National Academies Press: OpenBook

Noise and Military Service: Implications for Hearing Loss and Tinnitus (2006)

Chapter: 3 Noise and Noise-Induced Hearing Loss in the Military

« Previous: 2 Noise-Induced Hearing Loss
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

3
Noise and Noise-Induced Hearing Loss in the Military

The focus of this chapter is on noise and noise-induced hearing loss in theU.S. military. The committee was asked to identify sources of potentially damaging noise in the military setting and to review and assess available evidence on hearing loss incurred by members of the armed services as a result of noise exposure during military service since World War II. Concern about noise exposure and hearing loss among military personnel has been evident throughout this period (e.g., Glorig, 1952; Carmichael, 1955; CHABA, 1968; Yarington, 1968; Walden et al., 1971; Yankaskas and Shaw, 1999).

The first part of the chapter briefly reviews the services’ policies and programs to collect data on noise levels generated by equipment used by military personnel and the noise doses received by military personnel working in certain settings. Examples of the kinds of data collected through these efforts are provided. The remainder of the chapter focuses on the committee’s assessment of data on hearing thresholds and hearing loss among military service members since World War II.

NOISE IN THE MILITARY ENVIRONMENT

The sources of noise in the military are as varied as the activities carried out by the members of the Army, Navy, Air Force, Marine Corps, and Coast Guard. Obvious sources of potentially hazardous noise are weapons systems and jet engines, but vehicles, other aircraft, watercraft, communication systems, and industrial-type activities also serve as sources of potentially damaging noise.

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

Collection of Data on Noise Levels and Estimated Noise Exposures

Since World War II, numerous measurements of the sound pressure levels in proximity to various weapon systems and other military equipment have been collected. In addition, information has been collected on estimated noise doses for personnel working in steady-state noise. In the late 1970s, the Department of Defense (DoD) established, as part of an overall hearing conservation program, a department-wide requirement for periodic surveys of noise-hazardous environments and, subsequently, requirements for noise dosimetry. Each military service was responsible for collecting and maintaining information about hazardous noise environments and noise exposures. Many military sites had been collecting such information well before the DoD requirements were put in place. This section briefly reviews DoD-level requirements concerning measurement of noise levels and noise exposure. It also reviews the services’ data collection activities and the availability of these data. Noise-exposure limits are discussed in Chapter 5.

Department of Defense Requirements

In 1978, DoD established a requirement that each of the military services conduct sound surveys to identify and periodically monitor noise-hazardous environments (DoD, 1978). By 1987, the requirements included provisions for measuring noise exposures for workers exposed to noise levels of 85 dBA or more (DoD, 1987). Also included were separate specifications for the measurement of impulse noise and performance criteria for the measurement devices to be used. The current requirements, contained in DoD Instruction 6055.12, DoD Hearing Conservation Program, specify that sound pressure levels (SPLs) are to be measured in all potentially hazardous noise work areas at least once and within 30 days of any change in operations affecting noise levels (DoD, 2004).

Noise exposure (i.e., dose) is to be measured as time-weighted average (TWA) noise levels for military personnel working in industrial-type operations with hazardous noise levels.1 The surveys must be conducted by trained personnel using sound-level meters or dosimeters meeting or exceeding relevant standards established by the American National Standards Institute (ANSI). The DoD instruction does not require measurement of noise doses associated with military activities, whether actual operations or training exercises. Noise exposure during such activities can be highly variable, and typical dosimeters are not designed to capture the rapid rise to briefly sustained peak sound pressure levels in excess of 140 dB that occur

1  

The DoD instructions also apply to noise-exposed civilian workers.

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

with weapons fire and other impulse noise (e.g., Kardous and Willson, 2004).

Requirements for maintaining data from noise surveys and exposure assessments have changed over time. The initial requirement in 1978 was that data be maintained for 5 years. By 1987, the period had been extended to 30 years. In 1996, DoD specified that noise exposure data were to be maintained “for the duration of employment plus 40 years” (DoD, 1996).

DoD also has established design standards for noise levels of new materiel designed or purchased for the military services. In the most recent version of these standards (DoD, 1997), the stated purpose is to lead to equipment that minimizes noise-induced hearing loss, permits acceptable speech communication in a noisy environment, minimizes aural detection by an enemy, minimizes community annoyance, and provides acceptable habitability of personnel quarters (DoD, 1997). The design standards include limits for steady-state and impulse noise in occupied areas and noise from shipboard equipment and aircraft, including rotary-wing aircraft. However, for both new and older equipment used in “military-unique” settings,2 DoD regulations give priority to maintaining combat readiness and allow for tradeoffs between noise reduction and weight, speed, cost, or other factors crucial to the effectiveness of the equipment (DoD, 2004).

Air Force

The Air Force began requiring noise measurements in 1948 with its first regulation regarding hazardous noise: AFR 160-3, Precautionary Measures Against Noise Hazards (Gasaway, 1988). By 1956, regulations required the use of either direct measurement or published data to plot master plans of bases to indicate where exposure to hazardous noise might occur. Data on noise levels of aircraft and other power machinery were published periodically by the Wright Air Development Center at Wright-Patterson Air Force Base. One notable compendium contains measurements from within cockpit areas of hundreds of types and models of aircraft (Gasaway, 2002; also see Gasaway, 1986).

Dosimetry measurements began at selected airbases in the late 1970s (Fairman and Johnson, 1979). A 1982 Air Force regulation required evaluation of individual noise exposures for personnel whose exposure exceeded

2  

The term “military-unique” settings refers to DoD military and civilian operations and workplaces that are unique to the national defense mission (DoD, 1998). They include combat, combat training, and operation, testing, and maintenance of military equipment and systems, among which are weapons, aircraft, ships, submarines, missiles, ordnance, and tactical vehicles. The designation applies to such operations as peacekeeping missions, field maneuvers, naval operations, and military flight.

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

the equivalent of an 8-hour time-weighted average of 84 dBA (Department of the Air Force, 1982). For a group of employees doing similar work with similar noise exposures (referred to as a “similar exposure group”), it was and remains permissible to monitor the most highly exposed individual and to assign the resulting measurement to each group member, essentially a “worst case” assumption. Current noise evaluation procedures (Department of the Air Force, 1994) require dosimetry for a minimum of 3 worker-days (defined as one worker for 3 days, or three workers for 1 day) to identify the average daily exposure.

Starting in the late 1980s, various Air Force installations began automating their recordkeeping for sound pressure levels and dosimetry. In 2005, each installation continues to maintain its own database. The dosimetry data are used primarily for local shop or worksite decisions, or occasional installation-level uses. Compilation of such data across the entire Air Force is possible but is not done for routine analysis (Weisman, 2005).

Navy and Marine Corps

Navy requirements for the collection of noise survey data date back at least to a 1983 regulation requiring noise measurements and personal dosimetry with appropriate equipment and calibration (Department of the Navy, 1983). The Navy is also responsible for noise surveys for Marine Corps facilities. To date, data on sound pressure levels are routinely collected at Navy and Marine Corps facilities but are not routinely transferred to a central database.

Noise dosimetry data are routinely collected by local Navy medical units to perform exposure assessments and to make recommendations for placement of personnel into the hearing conservation program. Under current procedures, such noise exposure data, in the form of time-weighted average sound levels, must be provided to the exposed individuals, the command, and the entity providing medical surveillance (Navy Environmental Health Center, 2004b). Starting in 2002, noise dosimetry data collected for a variety of industrial, shipboard, and other naval operations, including Marine Corps activities, have been added annually to the Navy Occupational Exposure Database (Crowder, 2005). Some of these data date back to 1980. The data are not routinely used in the Navy’s overall hearing conservation program, but they are used on a case-by-case basis to respond to inquiries (Crowder, 2005).

Army

The Army has both a centralized program to evaluate the sound pressure levels of new weapons systems and equipment and a distributed pro-

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

gram for noise measurement and analysis at worksites at all Army installations. Through the centralized Health Hazard Assessment Program, begun in 1980, new equipment is tested to assess various potential hazards, including noise, chemicals, radiation, and vibration. The measurements of sound pressure levels are used to estimate likely time-weighted averages during use of the equipment, but noise dosimetry is not carried out as part of this program. The test information is used to make recommendations regarding the need for personal hearing protection as well as possible restrictions on training time with the systems (personal communication, F. Sachs, U.S. Army Center for Health Promotion and Preventive Medicine, August 18, 2004). The Army also has comprehensive data on sound pressure levels from weapons and equipment beginning from the 1970s and a more limited set of data going back to the 1960s.

In addition, each Army installation evaluates work environments for potential noise hazards from steady-state noise in industrial-type operations. Since 1988, the sound pressure level and noise dosimetry measurements have been collected in the Health Hazard Information Module database of the Army’s Occupational Health Management Information System. Dosimetry measurements are not routinely attempted for military-unique activities in the Army, in part because the impulse noise components are not readily measured by current instrumentation (U.S. Army Center for Health Promotion and Preventive Medicine, 1999; personal communication, D. Ohlin, U.S. Army Center for Health Promotion and Preventive Medicine, 2005).

Coast Guard

Coast Guard noise surveys were part of the Coast Guard hearing conservation program by the late 1960s and early 1970s (McConnell, 2004). Sound pressure level and noise dosimetry measurements made by the Coast Guard are provided to units in the form of written reports (McConnell, 2005).

Defense Occupational and Environmental Health Readiness System–Industrial Hygiene

In 2005, as this report was being written, all the services were still using their own databases on sound pressure levels and noise dosimetry. However, development of a DoD-wide database for recording, storing, and retrieving sound pressure level and noise dosimetry data, as well as information related to other occupational exposures, is in advanced stages. Introduction of the Defense Occupational and Environmental Health Readiness System–Industrial Hygiene (DOEHRS-IH) is planned for fall 2005 (personal communication, K. Wisniewski, U.S. Army Center for Health

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

Promotion and Preventive Medicine, February 2005). This database is intended to provide a longitudinal record of noise and other occupational exposures for DoD personnel.

Sound Levels and Noise Doses in the Military Environment

Information on noise sources and noise levels in the military environment is plentiful and detailed but not complete and not easily summarized. Sound levels vary depending on the distance from the sound source and the conditions under which the sound is being generated. Important characteristics of impulse noise include not only the peak sound pressure level, but the time pattern of the impulses and the frequency spectrum.

Table 3-1 provides examples of some of the measurements made since the 1950s of average sound levels found in ground vehicles and aircraft and peak sound pressure levels generated by certain weapons.3 On aircraft carriers, flight operations create an environment with combinations of aircraft noise, mechanical noise, and impact noise (Yankaskas and Shaw, 1999). Below the flight deck, sound levels have been measured at 106 dBA during aircraft launches. Exposure to high sound levels has also been reported for military personnel in positions such as radio operators (Robertson et al., 1990) and sonar technicians (Marshall and Carpenter, 1988) in the Navy and cryptolinguists in the Air Force (Ritter and Perkins, 2001). In addition, military personnel may encounter potentially damaging noise from equipment and activities comparable to those found in industrial settings, such as the operation of heavy equipment (Chandler and Fletcher, 1983). Data are also available on the acoustic spectra of some types of noise in the military environment (e.g., Johnson and Nixon, 1974; Gasaway, 2002), but they are not illustrated in Table 3-1.

The examples of noise levels associated with equipment and weaponry in the military included in Table 3-1 clearly demonstrate that there are many sources of high sound pressure levels in the military environment that exceed criteria for safe exposure. Data on sound pressure levels, however, are not sufficient by themselves to determine the noise dose received by an individual. As described above, dosimetry data have also been collected, but the committee found little published dosimetry data that could be used to draw conclusions about typical exposures (e.g., Fairman and Johnson, 1979; Jordan and Jones, 1983).

3  

Appendix F provides an illustrative list of documents, most of which are available in the published literature or in electronic form from government sources, that report sound levels generated by a variety of military aircraft, vehicles, equipment, and weapons systems.

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

TABLE 3-1 Examples of Sound Levels Associated with Military Equipment

a. Aircraft in Use in the 1950s

Name

Model

Location

Condition

Sound Level dBC/F

Sound Level dBA

 

Douglas Skyraider (USN; in use 1950s–1960s)

A-1J (AD-7)

Cockpit

Takeoff

132

128

Climb

118

117

Level

121

120

Cruise

113

109

Douglas Skyraider (USN)

A-1J (AD-7)

Passenger area

Taxi

87

81

Takeoff

111

111

Normal cruise

106

103

High cruise

109

108

NOTES: dBC/F, C-weighted or flat-weighted levels; dBA, A-weighted levels.

SOURCE: Gasaway (2002).

b. Military Equipment in Use in the 1960s

Name

Model

Location

Condition

Sound Level dB

Tanks

 

Interior

 

115 (±10)

Personnel carrier (APC)

 

Interior

 

120 (±10)

NATO rifle

M-14

Operator’s right ear

20 rounds, full automatic

159

3.7-in rocket launcher (bazooka)

 

Operator’s right ear

 

163

105mm howitzer

 

 

 

190 (impulse)

Sergeant missile

 

100 ft from launch site

 

145

Helicopter (Shawnee)

H-21C

Crew chief, 15-20 ft from aircraft

Rotor engaged

110

 

SOURCE: Adapted from Yarington (1968).

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

c.Flight Operations at Landing Signal Officer Platform, U.S. Navy Aircraft Carrier, 1970s

Event (n)

Aircraft

Average Noise Level dB(SPL)

Noise Level dBA

Average Duration at ≥ 90 dBA (seconds per event)

Trap (35)

F4

128

122

5

Trap (1)

A7

123

114

4

Trap (2)

C1

114

108

5

Bolter (6)

F4

120

116

5

Wave-off (8)

F4

125

124

5

Touch and go (10)

F4

129

121

4

Deck launch (2)

C1

127

123

20

 

SOURCE: Robertson et al. (1978a).

d. Military Equipment in Use in 2005

Army Vehicles

Model

Condition

Location

Speed km/hr (mph)

Sound Level dBA

High-mobility multipurpose wheeled vehicle (HMMWV), non-heavy variants

M966, also: M996, M997, M998, M1037, and others

2/3 payload

Crew positions

0(idle)

78

48(30)

84

88(55)

94

HMMWV, heavy variant

M1097, M1097A2, M1113, M1114

2/3 payload

Crew positions

Up to 50(31)

< 85

64(40)

88

80(50)

92

96(60)

98

HMMWV heavy variant

M1097

Full payload

Crew positions

Up to 40(25)

< 85

96(60)

100

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

Army Vehicles

Model

Condition

Location

Speed km/hr (mph)

Sound Level dBA

Commercial utility cargo vehicle

M1008, M1009, M1010, M1028

 

In cab

Below 88(55)

< 85

88(55)

85–91

Ambulance

M1010

 

Patient areas

All speeds

< 85

Armored personnel carrier, A3 version

M113A3 family, including M106A2, M1064A3, M1059A3, M58A3, M730A2, M901A3, M981A3

 

 

Idle

85–92

16(10)

106

32(20)

109

48(30)

114

63(40)

118

Abrams tank

M1A2, M1, M1A1

 

In vehicle

Idle

93

Tactical idle

103

16(10)

108

48(30)

114

63(40)

117

Army Helicopters

Model

Sound Level Location

dBA

Chinook

CH-47D

Cockpit

103

Blackhawk

UH-60A

Pilot

106

Copilot

106

Apache

YAH-64

Pilot

104

Copilot

101

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

Weapons (Impulse Noise)

Model

Condition

Location

Sound Level dBP

9mm pistol

M9

 

Shooter

157

5.56mm rifle

M16A2

 

Shooter

157

5.56mm squad automatic weapon fired from HMMWV

M249

 

Gunner

160

7.62mm machine gun

M60

Fired from HMMWV

Gunner

155

0.50 caliber machine gun

M2

Fired from HMMWV

Gunner

153

Machine gun

MK 19, Mod 3

Fired from HMMWV

Gunner

145

Grenade

M26

 

At 50 ft

164

MAAWS recoilless rifle

M3

 

Gunner

190

Light antitank weapon

M72A3

 

Gunner

182

Javelin antitank missile

 

Open position

Gunner

160

Enclosed position

Gunner

166

Fighting position

Gunner

172

105mm towed howitzer

Ml 19

At charge 8

Gunner

183

155mm towed howitzer

M198

Firing M203 propellant

Gunner

178

NOTES: In flight, helicopter crews wear helmets with integral hearing protectors. Passengers must rely on their own hearing protectors (e.g., earplugs) or ones supplied by air operations. HMMWV, high-mobility multipurpose wheeled vehicle; MAAWS, multi-role anti-armor anti-personnel weapon system.

SOURCE: Adapted from U.S. Army Center for Health Promotion and Preventive Medicine (2004d).

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

Estimating Cumulative Noise Exposures

Despite the existence of data on sound pressure levels generated by weapons and equipment, and dosimetry estimates of noise exposure for certain personnel, arriving at an estimate of the cumulative noise exposure of any service member or group of service members is nearly impossible. To an even greater extent than civilian workers, military personnel are not likely to experience homogeneous noise exposures over the course of their military service.

The impulsive and intermittent nature of many military noise exposures (e.g., gunfire, plane launches and landings, tank operation, 6-month shipboard deployments) adds an element of uncertainty to considerations of exposure and effect. For example, “high noise levels” for about 3 hours of a 14-hour period have been described as typical of high-tempo flight operations on an aircraft carrier (Yankaskas and Shaw, 1999). As discussed in Chapter 2, intermittent noise exposure may permit recuperation, thus ameliorating to some extent the hazardous effect of noise exposures. However, military personnel may also have noise exposures that are prolonged compared to those of civilians. At sea, for example, sailors are exposed to ambient shipboard noise continuously and may encounter potentially hazardous noise levels even in their sleeping quarters, giving their auditory systems no opportunity for short-term recovery (Yankaskas and Shaw, 1999; Yankaskas, 2001, 2004).

Even for personnel assigned to a specific occupational specialty, it is reasonable to assume that the typical activities for an individual vary over time and that the activities at any given time vary among personnel at different military installations. In addition, members of the military frequently change assignments and may be exposed to different degrees of noise hazard in different work settings. Among a sample of Navy enlisted personnel who served during the period 1982–2004 and were still serving after 2001, for example, the average length of service was 80 months, and time on shore duty averaged 40 months (Shaw and Trost, 2005). Finally, as described in detail in Chapter 5, wide variations in the effective use of hearing protection devices among military personnel can dramatically affect an individual’s noise exposure.

In sum, despite the availability of data on sound pressure levels and some dosimetry data, the complexity of military noise exposures precludes ready estimates of service members’ cumulative noise doses.


FINDING: The evidence is sufficient to conclude that hazardous noise levels are and have been present in many military settings.


FINDING: Extensive collections of data on sound pressure levels produced by equipment and activities in military settings are available from World War II to the present. Many estimates of noise exposures (doses)

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

from specific activities also are available from more restricted time periods. However, because of the changing nature of assignments in the military, the unpredictable aspects of military training and combat, the intermittent nature of many military noise exposures, and the sporadic use of hearing protection while in the military, these data do not provide a sufficient basis for estimating cumulative noise exposures over the course of military service for individuals or for subgroups (e.g., occupational specialties, branches, or eras).

EVIDENCE REGARDING THE EFFECTS OF NOISE ON HEARING AMONG U.S. MILITARY PERSONNEL

The committee was asked to review the evidence that hearing loss has been incurred by members of the armed services as a result of noise exposures during military service since World War II. To investigate this subject, the committee examined information from various sources, including studies reported in the published literature, reports prepared for the military services, and data from the military services’ hearing conservation databases, which were provided at the request of the committee. The committee also undertook additional analyses of some of the data.

The available information proved to offer an incomplete picture of changes in hearing thresholds over the course of military service and virtually no direct measures of the noise exposure or noise dose for individuals or groups. In the remainder of the chapter, the nature of the available data and their limitations are discussed, followed by a review of the data examined by the committee and presentation of the committee’s conclusions.

Studying Noise-Induced Hearing Loss Among Military Personnel

Potentially damaging noise exists in the military environment, but assessing its effects on the hearing of military personnel is not straightforward. Predictive formulas have been adopted as a basis for estimating the amount of hearing loss to be expected in an industrial population exposed to specified levels and durations of occupational noise (i.e., ISO-1999 [ISO, 1990]; ANSI S3.44 [ANSI, 1996]), but they are based on assumptions of exposures to noise of up to 8 hours per day, 5 days per week, and for periods of 10 to 40 years. Frequently, noise exposures in military settings do not conform to these conditions.

An alternative would be to have longitudinal data obtained using consistent measurement tools to track noise doses and hearing thresholds for individual military service members, or at least defined subgroups, over the course of their military service. Other factors that might affect hearing would also have to be taken into account, including nonoccupational noise

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

exposures. Such analyses have not been conducted and are impossible with the existing data.

In the studies reviewed by the committee, two approaches primarily have been used to assess risk of noise-induced hearing loss in the military. They are: (1) measurement of noise doses and estimation of the hearing loss expected from the measured dosages; and (2) measurement of pure-tone hearing thresholds in groups of military personnel. In the latter case, the data may consist of the actual thresholds measured at several frequencies or the relative shift in thresholds over some period of time.

Noise Doses

Comprehensive data on cumulative noise doses received by individual service members are not available. Furthermore, as discussed above, the available dosimetry data are selective and not in a form that would support reasonable efforts to incorporate them in analyses of noise-induced hearing loss.

As an alternative, some studies use data on short-term noise doses or sound levels in given settings. Other indicators, such as military occupational categories, are also used. If the categories are broad, however, it may be difficult to know if there are significant variations in actual noise exposures within each group. A range of noise exposures within groups would tend to blur distinctions among groups.

In addition, differences in age or length of service cannot be assumed to correspond to differences in the amount of noise exposure. Personnel showing signs of threshold shifts may be moved to jobs with lower noise levels. Those who remain in military service for longer periods may move into lower noise assignments. Use of hearing protection can vary over time and among groups. Many recent analyses have been based on data for personnel who are enrolled in the services’ hearing conservation programs and, by definition, considered to be at risk for damaging noise exposures. However, their effective noise doses are not necessarily greater than those of other personnel because of the protective measures that are part of the hearing conservation program. There is also no information from which to assess whether noise exposures at a given age or length of service are comparable in personnel who have served in different eras.

Measurement of Hearing Thresholds

Threshold data from periodic hearing tests have been recorded in service members’ individual medical records since the 1950s. Service members’ medical records may also include the results of annual tests conducted in conjunction with the services’ hearing conservation programs. Access to

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

these data is often difficult or impractical, and only limited use has been made of them for analytic studies.4 Some of the studies reviewed by the committee used actual databases from the hearing conservation programs, but others relied on test data collected specifically for the study or for some other purpose. Most of the reports reviewed were cross-sectional analyses.

The committee focused on reports from the 1970s and later, although a few earlier studies are noted. The emphasis on the more recent data reflects, in part, the evolution of audiometric testing standards and equipment between World War II and 1970. Data collected since the 1970s are considered more reliable and consistent than earlier data, although changes since then, such as the shift from self-recording audiometers to microprocessor-based audiometers, could affect the comparability of measurements. Differences may also exist among data sources in the range of values recorded during hearing testing, with the military seldom using levels below 0 dB HL.

No specific metric has been developed to establish unequivocal evidence for the presence of noise-induced hearing loss. A primary indicator of the presence of noise-induced hearing loss is the pattern of hearing loss in the high frequencies, referred as the “noise notch,” in which hearing thresholds at 3000, 4000, or 6000 Hz are worse than those at lower frequencies or at 8000 Hz. Chapter 2 described work being done to try to define a “notch index” that may characterize such notches quantitatively, but currently, a variety of approaches are used to present data in studies of noise-induced hearing loss.

Frequently, data reviewed by the committee were presented in terms of group averages, such as mean or median values for thresholds at individual frequencies or groups of frequencies (e.g., 3000, 4000, and 6000 Hz). These averages obscure the variation within the group. A few reports provided data on the distribution of pure-tone thresholds at various frequencies, making it possible to determine the percentage of the group whose thresholds exceeded specific values. Some reports for Army and Air Force personnel also included the percentage of personnel whose thresholds met criteria for hearing-loss classification systems used in medical fitness profiles.

In many cases, threshold data available to the committee were not measured pure-tone thresholds, but the percentages of personnel in the services’ hearing conservation programs who experienced a significant threshold shift (STS). STS provides an indication of the relative changes in

4  

The present Institute of Medicine study included a review of audiometric reports contained in the medical records of a sample of veterans. That review focused on procedural aspects of the testing and reporting, not the audiometric results. The findings from the record review are discussed in Chapter 6.

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

hearing thresholds from baseline measurements following some unspecified period of time (usually, at least 1 year). Follow-up testing is required to determine whether the threshold shift is permanent.

An STS indicates only that a change in hearing of at least a certain magnitude has occurred. It does not capture the amount of change or the new hearing thresholds. The committee received annual STS data from the services’ hearing conservation programs and also reviewed published reports on STS in the military. Although the data are potentially useful, several administrative problems make their validity suspect at present. Those problems are described below.

Comparisons between groups are also used to explore the effects of differences in exposures. The committee undertook age-specific comparisons of average high-frequency thresholds among specific groups of military personnel and those in a reference population. The group data available to the committee permit only a limited analysis. The committee identified a small number of other studies that were able to go further and explore the likelihood of finding hearing loss among military veterans on the basis of data for individuals and that used statistical methods to account for other relevant differences among the members of the comparison groups. One study examined the risk of hearing loss among veterans with and without service in Vietnam. The other study compared veterans and nonveterans.

Most of the reports of hearing thresholds in the military reviewed by the committee, including reports on STS, are based on a single measurement at a specific point in time and are not appropriate for drawing conclusions about longitudinal trends. Comparisons of age groups within studies or across studies conducted at different times are subject to the cohort effects of differences over time in the characteristics and exposures of the members of the groups, as well as differences in data definitions, measurement tools, and other aspects of data collection. In studying noise-induced hearing loss in the military population during the 60 years since World War II, a few important considerations include the irregular timing of armed conflicts and changes in hearing conservation programs, audiometer technology, and the types of hearing protection available (see Table 3-2).

In summary, there are no data that permit a comprehensive review of noise-induced hearing loss experienced by military personnel in each of the armed services during the period since World War II. Most of the data identified by the committee came from cross-sectional reports of average (a mix of mean and median) hearing levels among various categories of service members. The reports typically provided data stratified by age or length of service. The committee reviewed at least 12 such reports. (See Table D-5 in Appendix D for summary information on the features of these reports.) No data on Coast Guard personnel were available to the committee. Only very

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

TABLE 3-2 Time Line of Major Conflicts, Milestones in Hearing Conservation Programs, and Hearing Protection Devices

Year

Major Conflicts

Hearing Conservation Milestones

Hearing Protection Available

1941

World War II begins

 

Cotton, fingers, or no protection

1945

World War II ends

 

Some early hearing protection available: V-51R, early earmuffs

1948

 

Air Force issues first regulation concerning hazardous noise

 

1950

Korean War begins

1950s: Introduction and increasing use of pure-tone audiometry

 

1953

Korean War ends

 

 

1956

 

Air Force introduces first of services’ hearing conservation programs

 

1960

 

Pure-tone audiometry replaces whisper test for screening military applicants

1960s: V-51R, triple-flange earplugs, improved earmuffs

1964

Vietnam War begins

 

 

1970

 

First Navy comprehensive hearing conservation program

Air Force begins automated handling and storage of audiometric monitoring data (late 1974)

1970s: Same earplugs and earmuffs, new foam earplugs, helmets with noise attenuation introduced

1975

Vietnam War ends

 

 

1978

 

DoD Instruction establishing hearing conservation programs

 

1980

 

First comprehensive Army hearing conservation program

Army begins data repository for audiometric data

1980s: Conventional earplugs and muffs same as 1960s and 1970s; some tanker helmets introduced with active noise reduction (ANR) included

1983

 

OSHA Final Noise Standard

 

1990

Gulf War deployments begin: Operation Desert Shield

 

1990s: Performance of existing earplugs and muffs essentially the same; new use of earphone in foam earplugs for tank and helicopter communication under helmet

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

Year

Major Conflicts

Hearing Conservation Milestones

Hearing Protection Available

1991

Gulf War: Operation Desert Storm

Gulf War ends

 

Widespread use of ANR in tanker helmets, some in aircraft flight helmets

1999

 

Introduction of DOEHRS-HC to standardize audiometric data repositories across services

 

2001

War on Terrorism: Operation Enduring Freedom (Afghanistan) begins

 

2000s: Introduction of noise-level-dependent earplugs (Combat Arms Earplug)

2003

War on Terrorism: Operation Iraqi Freedom begins

 

 

2004

 

Services adopt OSHA definition for STS

 

NOTES: Additional information on developments in hearing protection can be found in Table 5-2. DoD, Department of Defense; DOEHRS-HC, Defense Occupational and Environmental Health Readiness System-Hearing Conservation; OSHA, Occupational Safety and Health Administration; STS, significant threshold shift.

SOURCES: Gasaway (1988); Nixon (1998); personal communication, E. Berger, E-A-R/Aearo Company, March 2005; Department of Veterans Affairs (2005); Ohlin (2005).

limited data were available on women in the services, and many of the committee’s analyses were based on data for men alone. In some cases, including the reports from DOEHRS-HC on STS, data for men and women were not reported separately. Women have been a small proportion of the military population, but their numbers are increasing. It will be important to understand how their hearing loss experience compares with that of men to interpret changes in hearing thresholds over time.

Although the committee’s focus is on data since the 1970s, this is not to imply that there were no attempts to examine noise-induced hearing loss in the military by the scientific community prior to this era (e.g., Glorig et al., 1957; Solomon and Fletcher, 1958). Rather, the 1970s represent the initial period for which substantial amounts of hearing-threshold data, obtained with appropriate equipment and procedures, became available from reasonable samples of personnel and from multiple branches of the military.

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

The next section presents the data reported since 1970 on the average hearing thresholds measured in military personnel from various branches of the military. This is followed by presentation of data on the variations in hearing thresholds across personnel over this same time period.

EVIDENCE BASED ON AVERAGE HEARING THRESHOLDS

Following a brief presentation of results for the special case of acoustic trauma, average pure-tone hearing thresholds across frequency are presented for groups of military personnel. This section concludes with the presentation of several summaries of average hearing thresholds for several branches of the military.

Acoustic Trauma

Acoustic trauma presents, perhaps, the clearest cause-and-effect link between noise exposure and hearing loss. Even in those cases, however, the amount of change in hearing thresholds as a result of that event cannot be determined conclusively without information about preexposure thresholds. The committee found no systematic data on the number of events that occur among U.S. military personnel, and acoustic trauma has not been a reportable injury for military personnel (AMSA, 1998; Ohlin, 2004a). Reports of hearing loss among 62 percent of personnel with blast injuries who were treated at Walter Reed Army Medical Center from March 2003 through May 2005 (n = 414) (Chandler, 2005) provide an indication that acoustic trauma is occurring, and likely occurred in the past, but does not provide sufficient evidence to estimate its overall incidence. It is likely that cases of hearing loss resulting from acoustic trauma are included in the remainder of the data discussed.

Average Thresholds

Examples of Noise-Notch Patterns of Hearing Loss Among Military Personnel

The earliest data examined in detail were from studies of Army personnel in combat arms branches—infantry, armor, and artillery (Walden et al., 1971; Walden et al.,1975). An initial pilot study in 1971 was followed in 1974 by a more systematic study based on a random sample of Army enlisted personnel in these three branches at 10 posts. The mean hearing levels for the three groups were similar, with those for armor personnel lying between those for the artillery and infantry personnel. Figure 3-1 illustrates the average hearing thresholds as a function of frequency for

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

FIGURE 3-1 Mean hearing thresholds (left ear) for Army enlisted men serving in 1974 in the infantry, by frequency and length-of-service group. Error bars for one standard deviation toward better hearing are shown at each frequency for the 2-year length-of-service group. Error bars for one standard deviation toward worse hearing are shown at each frequency for the 20-year length-of-service group.

SOURCE: Walden et al. (1975).

infantry personnel in 1974 (Walden et al., 1975). The pilot study (Walden et al., 1971) found similar hearing levels among a mixed population of officers and enlisted personnel from these three branches.

The data plotted in Figure 3-1 are the mean hearing thresholds in the left ear at each frequency tested, by length-of-service (LOS) categories. In this study, the left-ear data represent the “worse ear,” a pattern observed in most of the reports reviewed and one that is common with exposure to gunfire. The difference between left and right ears, however, was seldom more than a few decibels.

The audiometric configuration shows the notch at higher frequencies that serves as a hallmark of noise-induced hearing loss. The hearing thresh-

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

olds are poorest at 6000 Hz, a pattern seen in the other reports reviewed by the committee and reported previously for military noise exposures (e.g., Gravendeel and Plomp, 1959; Ylikoski and Ylikoski, 1994). There is a fairly broad maximum for the hearing loss that spans from about 3000 Hz to 8000 Hz. The pattern can be seen for all lengths of service, with worse thresholds at nearly all frequencies for those with longer service. The pattern of greater differences in hearing thresholds among groups with shorter lengths of service, up to 10–15 years, and smaller differences among groups with longer service, has also been commonly observed in studies of industrial noise-induced hearing loss (see Chapter 2).

Frequency-specific data from the 1970s were also available for certain personnel in the Navy (Robertson et al., 1978b) and Air Force (Sutherland and Gasaway, 1978). The Navy data were for enlisted personnel in 16 occupational specialties (referred to in the Navy as ratings), representing about 20 percent of all rating categories. The Air Force data (median thresholds) were from audiometric testing done for the hearing conservation program in 1975–1976. The Navy data were reported by length of service, whereas the Air Force report used age. In both the Navy and Air Force data, maximum hearing thresholds were at 6000 Hz, with a fairly broad maximum beginning at 3000 Hz. An upturn at 8000 Hz, a characteristic of the noise notch, could be seen in the Navy data, but Air Force personnel were not tested at that frequency. The average hearing thresholds were higher with greater length of service or at older ages. However, the thresholds for Air Force personnel were consistently better than those for Army and Navy personnel in comparable age/LOS groups.

Unfortunately, measures of hearing thresholds obtained from military personnel after the 1970s no longer included 8000 Hz as a test frequency. As a result, it is unclear whether a “notch” exists in the average data, given that the notch typically occurred at 6000 Hz when threshold measurements included 8000 Hz. This situation is illustrated by the data in Figure 3-2, which depicts the average hearing thresholds through 6000 Hz from Bohnker et al. (2002) for 51,643 individuals enrolled in the Navy’s hearing conservation program in 1995–1999. A noise notch is not apparent in these average data.

Summary of Average Hearing-Threshold Data for the 1970s, 1980s, and 1990s

For the most part, large-scale studies of hearing loss from multiple branches of the military using reliable and valid measurement procedures and conditions were not available until the 1970s. In nearly all of these studies, data were gathered from military personnel grouped according to age, length of service, or both. In the few reports that used only length of

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

FIGURE 3-2 Mean hearing thresholds (left ear) for enlisted men enrolled in the Navy hearing conservation program, by frequency and age group, 1995–1999. Error bars for one standard deviation toward better hearing are shown at each frequency for the age group 17–24 years. Error bars for one standard deviation toward worse hearing are shown at each frequency for the age group 40–44 years. Data for age groups of 45–49 years and 50 years or older are not shown in this figure due to smaller sample sizes compared to those age groups depicted.

SOURCE: Bohnker et al. (2002).

service, age at entry into military service was assumed to be 18 years and length of service was assumed to be correlated with age. To assess average hearing thresholds of military personnel in various age groups, it is necessary to compare these results to the average hearing thresholds of similar age groups from the general population.

Accordingly, the committee examined age-specific comparisons between the average hearing thresholds for certain groups of military personnel and those of two reference groups of the same average age. As noted in Chapter 2, there are essentially two types of reference datasets available on age-

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

related hearing loss. One is based on an unscreened sample that may include people who have a history of certain types of otologic disease or noise exposure. The other type is a screened sample that is designed to exclude such individuals. For an unscreened reference point, the committee used data drawn from the results of a U.S. Public Health Service (USPHS) survey completed in 1962, whose participants were a nationally representative sample (n = 6,672) of the civilian adult population in the United States at that time (Glorig and Roberts, 1965).5 The better-ear thresholds from the 1962 USPHS study comprise database B from the ISO-1999 standard, but most of the studies of military personnel did not report better-ear thresholds. As a result, the reference set of data from the 1962 USPHS study was used to derive an average amount of hearing loss for both ears for each age group. The screened sample used was database A from the ISO-1999 standard (ISO, 1990). For both the screened and unscreened reference data, the specific measure used for comparison was an average high-frequency threshold, calculated as the arithmetic average of the mean or median (depending on the source) thresholds at 3000, 4000, and 6000 Hz, for both ears combined. This average was selected to focus on the frequencies most closely associated with noise-induced hearing loss.

When determining the effects of industrial or military noise on hearing, one would prefer that the reference or comparison data be obtained from a non-noise-exposed sample that was otherwise identical to the noise-exposed sample. Military personnel are subjected to a hearing-related screening that is less rigorous than that in studies of “screened” samples, but possibly more rigorous than that of “unscreened” samples (e.g., Robertson et al., 1978b; AMSARA, 2002). Thus, it is unclear which reference group would be the most appropriate to use for comparison to the hearing thresholds measured in military personnel.

One approach to resolving this is to compare the hearing thresholds of recruits prior to military noise exposure to those thresholds observed in screened and unscreened samples of the same age. An initial comparison found that the thresholds for men, ages 18–24 years, in the unscreened data were comparable to those of small groups of Army (n = 246) and Navy (n = 121) recruits of similar age (Walden et al., 1971; Robertson et al., 1978b). Similar thresholds were also reported for a larger group of Army recruits (n = 3,534) at a later date (Ohlin, 1992), suggesting no marked change over this period in the baseline hearing thresholds for Army personnel and, therefore, correspondence with the thresholds from the 1962 Public Health Service study. The average thresholds for both the Army and

5  

The reported thresholds were corrected to reflect the values for audiometric zero that were adopted in 1969 (ANSI, 1969).

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

Navy recruits, as well as the corresponding age group from the 1962 USPHS study, were approximately 5–10 dB HL in the low and mid frequencies, increasing to about 15–20 dB HL at 6000 Hz. The average thresholds for a screened sample of this age would basically be 0 dB HL at all frequencies. Thus, at entry into military service, these samples of recruits from the Army and Navy appear to have average hearing thresholds equivalent to those of a separate group of unscreened young adults of similar age from the 1962 USPHS study.

Figure 3-3 displays data on age-specific average high-frequency hearing thresholds in various groups of Army personnel in the 1970s and early and late 1980s, along with the thresholds for the two sets of reference data. The data from the two relatively large studies (n ~ 3,000) in the 1970s (Walden et al., 1971; Walden et al., 1975) show average high-frequency thresholds that are similar for men in the infantry, artillery, and armor branches, all of whom were considered to have had high noise doses. Those thresholds exceed the unscreened reference thresholds by greater amounts at older ages, a pattern consistent with noise-induced hearing loss in excess of expected age-related changes alone. A similar study (Ohlin, 1992) examined data from 1989 for enlisted men from the same three branches who were enrolled in the Army’s hearing conservation program. Average thresholds were lower at every age compared with the 1970s data, but exceeded the unscreened reference levels by 3–5 dB. Factors contributing to the change in thresholds between 1974 and 1989 may have included not only differences in noise exposure or use of hearing protection, but also unidentified selection effects in hearing conservation registry data and demographic differences arising from a higher percentage of black soldiers in the population in 1989 (Ohlin, 1992; Henselman et al., 1995). Hearing thresholds for blacks have been observed to be lower than those for whites (Royster et al., 1978).

Figure 3-3 also includes data from studies with smaller sample sizes from the early 1980s. Army engineers (n = 209) in various occupational specialties generally had thresholds similar to the 1970s data (Chandler and Fletcher, 1983). Average high-frequency thresholds for two small groups of Army aviators, however, were generally similar to those in the unscreened comparison (Walden et al., 1971; Peters and Ford, 1983). Another study used Army hearing conservation registry data for 1989 to compare, by race, hearing thresholds of enlisted men presumed to be exposed to high noise levels (i.e., in the armor, artillery, and infantry branches; n = 39,006) or to low noise levels (e.g., personnel in administration, supply and services, public affairs; n = 18,730) (Henselman et al., 1995). These data represented 25 percent of soldiers in the noise-exposed branches and 18 percent of the soldiers in the non-noise-exposed occupational groups. Because the results were reported in terms of average age-corrected thresholds at 1000, 2000, 3000, and 4000 Hz, they were not comparable to the data from the studies

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

FIGURE 3-3 Average high-frequency thresholds for both ears (arithmetic average of mean values at 3000, 4000, and 6000 Hz in both ears), by age, for selected groups of Army personnel during the 1970s, 1980s, and 1990s. The Army data plotted are for a 1971 pilot study (◊); a sample of recruits (R) and enlisted men in the infantry (○), armor (∇), and artillery (☐) branches in 1974; small groups of engineers (+) and aviators (×) in the early 1980s; and enlisted men from the infantry, armor, and artillery enrolled in the hearing conservation program in 1989 (★). Average high-frequency thresholds for men from screened (A; ISO-1999, 1990) and unscreened (U; Glorig and Roberts, 1965) reference groups are also shown.

SOURCES: Glorig and Roberts (1965); Walden et al. (1971); Walden et al. (1975); Chandler and Fletcher (1983); Peters and Ford (1983); ISO (1990); Ohlin (1992).

described above and displayed in Figure 3-3. For all soldiers, the difference in age-corrected average thresholds between those with high and low noise exposure was less than 5 dB, regardless of length of service.

Figure 3-4 shows data for certain Navy personnel from the 1970s (n = 3,050) and 1990s (n = 51,643). The earlier data (Robertson et al., 1978b) for enlisted personnel in 16 occupational specialties show average high-frequency thresholds that exceed those for the unscreened reference. With a

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

FIGURE 3-4 Average high-frequency thresholds for both ears for selected Navy enlisted personnel in the 1970s and for Navy enlisted men enrolled in the hearing conservation program in 1995–1999 (●). The 1970s data are for eight occupational specialties considered to have high noise exposure (□) and eight considered to have low noise exposure (○), plus recruits (R). Average high-frequency thresholds for men for screened (A; ISO-1999, 1990) and unscreened (U; Glorig and Roberts, 1965) reference groups are also shown.

SOURCES: Glorig and Roberts (1965); Robertson et al. (1978b); ISO (1990); Bohnker et al. (2002).

few exceptions, however, the thresholds for eight occupational specialties thought to have the least noise exposure are within 3 to 5 dB of those for the unscreened reference. The eight specialties thought to have the most noise exposure generally had higher average thresholds than the low-noise groups, but Robertson and colleagues noted more overlap between the high- and low-noise groups than had been anticipated. The thresholds for older Navy personnel, even for the presumed high-noise job specialties, are better than those observed in the 1970s Army data (see Figure 3-3). In more recent data for enlisted men in the Navy’s hearing conservation program

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

during the period 1995–1999 (Bohnker et al., 2002), average high-frequency thresholds are slightly better than those in the unscreened sample.

The available data from both the 1970s and the 1990s for Marine Corps personnel (Figure 3-5) (Goldenberg, 1977; Bohnker et al., 2002) and Air Force personnel (Figure 3-6) (Sutherland and Gasaway, 1978; Thomas, 1995) show average high-frequency thresholds that were similar to or somewhat better than those for the unscreened sample. All the Air Force data are for participants in the hearing conservation program. The more recent Marine Corps data are also for participants in the hearing conservation

FIGURE 3-5 Average high-frequency thresholds for the better ear for selected Marine Corps personnel (officers and enlisted men) in the 1970s (○) and for both ears for enlisted Marine Corps men in the hearing conservation program in 1995–1999 (●). Average high-frequency thresholds (both ears) for men for screened (A; ISO-1999, 1990) and unscreened (U; Glorig and Roberts, 1965) reference groups are also shown.

SOURCES: Glorig and Roberts (1965); Goldenberg (1977); ISO (1990); Bohnker et al. (2002).

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

FIGURE 3-6 Average high-frequency thresholds for Air Force personnel enrolled in the hearing conservation program in 1975 (○), 1975–1976 ( ), and 1995 (●). Average high-frequency thresholds for men for screened (A; ISO-1999, 1990) and unscreened (U; Glorig and Roberts, 1965) reference groups are also shown.

SOURCES: Glorig and Roberts (1965); Sutherland and Gasaway (1976, 1978); ISO (1990); Thomas (1995).

program. The earlier data (available for the better ear only) are for Marine Corps officers and enlisted personnel tested at a single base. The committee was surprised by the comparability of the Marine Corps thresholds to the unscreened comparison and the contrast with the higher thresholds seen in the 1970s data for Army personnel in infantry, artillery, and armor specialties. The committee had no information on baseline thresholds of Marine Corps personnel, the effect of the inclusion of officers in the Marine Corps study population (versus only enlisted personnel in the Army study), or unidentified selection factors that might have affected the characteristics of the populations tested. Information was also lacking on the distribution of thresholds (see below) and the difference between the better-ear thresholds

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

reported for the Marines and their average thresholds for both ears (the measure reported in Army study). These or other factors might help explain the difference between the data from the Marine Corps and the Army with regard to average high-frequency hearing loss.

EVIDENCE BASED ON VARIATIONS IN HEARING THRESHOLDS WITHIN GROUPS

The average thresholds do not reflect the variability within the group or the nature of the distribution of the data, so the committee also examined data describing the distribution of thresholds and other measures of variability within groups. As the data on hearing thresholds deviate increasingly from a normal distribution, typical measures of central tendency, such as the mean, become less representative of the group. For example, a set of normally distributed thresholds and a set of thresholds distributed with either positive or negative skewness may each have the same mean value, but the two underlying distributions would provide different interpretations with regard to the proportion of each sample who have noise-induced hearing loss. Generalizing from mean thresholds to thresholds for individuals is essentially impossible.

The committee’s work was limited by the lack of data available to examine the range of hearing thresholds within a given population. The limited data offering some indication of the distribution of hearing thresholds in military populations are reviewed here. This section begins with a discussion of the distributions of pure-tone thresholds. It then turns to a review of the proportion of individuals in the military identified with various categories of hearing loss. It concludes with a review of the annual incidence of STS among military personnel. In all of these analyses, the goal is to get a clearer picture of the proportion of military personnel who have or are developing noise-induced hearing loss.

Individual Variations of Hearing Thresholds in Military Personnel

Standard-deviation error bars, such as those shown in Figure 3-1 for the mean data for the groups of Army infantry personnel with the shortest and longest lengths of service, provide some indication of the range of the middle two-thirds of the distribution of individual hearing thresholds. That is, assuming a normal distribution of hearing thresholds, 68 percent of the individual data will be within one standard deviation of the mean threshold. Thus, although the average high-frequency hearing threshold for Army infantry personnel from 1974 with 2 years of service is slightly below 20 dB HL (Figure 3-1), the range representing the middle two-thirds of the group is from about 0 dB HL to 40 dB HL. As noted, however, such estimates are based on an assumption of a normal distribution, and the distributions of

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

pure-tone thresholds at each frequency are usually not normal, most often being negatively skewed. The negatively skewed distributions of pure-tone hearing thresholds may be attributable in part to the restricted range of hearing thresholds that can be measured below 0 dB HL due to limitations in the equipment or facilities.

The Air Force report (Sutherland and Gasaway, 1978) on hearing thresholds from 99,318 military personnel enrolled in the hearing conservation program, during the period June 1975 through May 1976, was one of the few reports to include the distribution of pure-tone thresholds at each frequency for each age group. In Figure 3-7, the solid line represents the median hearing threshold at each frequency for personnel ages 45–54 years. The dashed lines represent the 10th and 90th percentiles of the distribution

FIGURE 3-7 Hearing thresholds (left ear), by frequency, for personnel ages 45–54 years in the Air Force hearing conservation program, 1975–1976. The solid line and filled circles are the median pure-tone thresholds (50th percentile) at each frequency. The dashed lines represent the 10th and 90th percentiles.

SOURCE: Sutherland and Gasaway (1978).

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

of hearing thresholds at each frequency. At 4000 Hz and 6000 Hz, the median thresholds were approximately 28 dB HL, corresponding to a mild degree of hearing loss. However, the upper dashed line indicates that 10 percent of the members of this age group had thresholds that were about 5 dB HL or better at 4000 Hz and 6000 Hz, well within normal limits. The lower dashed line indicates that another 10 percent had thresholds of about 70 dB HL or worse, a severe hearing loss at these frequencies.

Is this broad range of hearing thresholds for 45- to 54-year-old military personnel in the Air Force unique to noise-induced hearing loss or typical for this age group? To address this question, Figure 3-8 provides a more detailed look at some of the results from this same Air Force report (Sutherland and Gasaway, 1978). In this figure, the distributions of pure-tone thresholds at 3000, 4000, and 6000 Hz for Air Force military personnel are shown by the solid lines in the left, center, and right columns, respectively. Distributions are shown for four of the five age groups included in the Air Force report. For the oldest group included in that report, 55–64 years of age, the sample size (n = 364) was much smaller than for the other age groups and not considered to be representative. As a result, these data were excluded from Figure 3-8. For comparison, similar distributions have been displayed in Figure 3-8 for the pure-tone thresholds for men from the 1962 USPHS data (dashed lines). At all three frequencies, 5 dB was subtracted from the hearing-threshold-level categories to correct the USPHS data to the ANSI (1969) standard values used in the Air Force report.6 For both the Air Force and the USPHS data, the distributions are of hearing thresholds obtained from the left ear.

Several general trends are apparent in these data. First, every distribution is negatively skewed with a much greater spread of hearing thresholds above the mean than below it. Second, for both sets of distributions, the amount of the spread in hearing thresholds increases as the age of the group increases. Third, although there is some evidence of an upward shift in the distribution of hearing thresholds for the military personnel in the Air Force relative to the USPHS data in the younger age groups, this has largely disappeared in the older age groups. Finally, at the younger age groups where the two distributions differ, the differences are confined primarily to differences in the distribution of normal-hearing thresholds (thresholds less than 25 dB HL).

To recap, the variability of hearing thresholds across military personnel in the Air Force was shown in Figure 3-7 to be quite large for the age group comprised of 45- to 54-year-olds, the group with the greatest amount of high-frequency hearing loss and a substantial sample size (n = 3,340). The

6  

The actual correction factors from ASA (1951) to ANSI (1969), including allowance for the difference in headphones used, are 5.6, 4.8, and 4 dB at 3000, 4000, and 6000 Hz, respectively (Sutherland and Gasaway, 1978).

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

FIGURE 3-8 Distributions of pure-tone thresholds from Air Force personnel enrolled in the hearing conservation program in 1975–1976 (solid lines) and from an unscreened sample of men in the general population (dashed lines) at 3000 (left column), 4000 (center column), and 6000 Hz (right column). Each row depicts the distributions for separate age groups from 18–24 years (top) to 45–54 years (bottom). All data are for hearing thresholds from the left ear.

SOURCES: Glorig and Roberts (1965); Sutherland and Gasaway (1978).

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

comparison of distributions of hearing thresholds for this age group from the Air Force to comparable data from the 1962 USPHS study in Figure 3-8, however, suggests that the observed variability in hearing thresholds across individuals in the Air Force is similar to that of an unscreened sample of the general population. Again, this raises the issue of the appropriate reference group to which one should compare thresholds from military personnel. Considering the average-threshold data for both ears presented previously for the Air Force (Figure 3-6) and the distribution of individual pure-tone thresholds for the left ear for the Air Force (Figure 3-8), military personnel in the Air Force in the 1970s do not appear to have hearing thresholds that differ substantially from an unscreened sample of the general population. Unfortunately, there are no other data available on the distribution of pure-tone thresholds for military personnel, especially for groups for whom the average hearing thresholds appear to be substantially worse than an unscreened sample of the general population (e.g., Army data from the 1970s, Figure 3-3).

Although other reports of additional data on the distributions of pure-tone thresholds in military personnel were not available, some reports did provide percentages for individuals in each of several age groups who had hearing thresholds greater than some criterion amount of hearing loss. Goldenberg (1977), for example, reported on the percentage of better-ear hearing thresholds that were greater than 25 dB HL among 11,580 Marine Corps personnel whose hearing was tested at one base during a 13-month period. These percentages for Marine Corps personnel are displayed by the dashed lines in Figure 3-9 for pure-tone frequencies of 3000, 4000, and 6000 Hz and each of five age groups. Percentages at lower frequencies were all at or below about 10 percent, even for the oldest age group, and are not of interest here. The solid lines in Figure 3-9 provide comparison percentages from the 1962 USPHS unscreened sample for better-ear pure-tone thresholds greater than 25 dB HL (adjusted to ANSI (1969) standards) at the same three frequencies and for the same five age groups.

Although there is excellent agreement between the two sets of data for the two younger age groups, similar to what had been observed previously in the average data for Army and Navy recruits, for the three older age groups, the percentage of Marines with hearing thresholds greater than 25 dB HL at each frequency exceeds that of the unscreened sample from the general population by 15–25 percent. Thus, although the average-threshold data (better ear) for this same sample of Marines were generally consistent with average data from the USPHS unscreened sample (both ears) (Figure 3-5), the limited distributional data available from this same report (Figure 3-9) suggest there were substantially more Marines over age 35 years who had at least a mild hearing loss (> 25 dB HL) in the high frequencies in their better ear than in corresponding age groups from an unscreened sample of the general population.

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

FIGURE 3-9 Percentages of each age group, from 18–24 years (left) to 55–64 years (right) having hearing thresholds greater than 25 dB HL at each of three pure-tone frequencies: 3000 Hz (3), 4000 Hz (4), and 6000 Hz (6). Dashed lines represent data from the better ear of Marines in the 1970s and the solid lines represent data for the better ear of men in an unscreened sample of the general population from the 1962 U.S. Public Health Service survey.

SOURCES: Glorig and Roberts (1965); Goldenberg (1977).

Another study, by Robertson and colleagues (1978b), measured hearing thresholds in 3,050 Navy military personnel and defined a significant high-frequency hearing loss as an average threshold at 3000, 4000, and 6000 Hz ≥ 30 dB HL. Among personnel with more than 5 years of service, 37 percent of those in the high-noise occupational specialties and 23 percent of those in the low-noise occupational specialties had a significant high-frequency hearing loss. Unfortunately, there are no comparable percentages from the 1962 USPHS sample to which these values from the Navy can be compared to determine if such percentages are greater than expected in the general population.

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

The Army and the Air Force include criteria for hearing in a classification system used to characterize the medical fitness of service members. For hearing, these ratings, known as profiles, vary from H-1 (closest to normal hearing) to H-4 (the most severe hearing loss). The Army’s current criteria for an H-1 profile are an average threshold in each ear of ≤ 25 dB HL for the frequencies 500, 1000, and 2000 Hz; no individual threshold > 30 dB HL at these frequencies; and a threshold of ≤ 45 dB HL at 4000 Hz (Department of the Army, 2003). Thus, having an H-1 profile means having normal or near-normal hearing for low and middle frequencies (500–2000 Hz) in both ears, but moderate hearing losses are possible at 4000 Hz and profound hearing losses are possible at 6000 and 8000 Hz. Thus, H-1 classification is not synonymous with “normal” hearing (see Chapter 1).

Data for the Army from the 1970s for personnel in the infantry, armor, and artillery indicate that 20 to 30 percent were classified as H-2 or worse (Walden et al., 1971; Walden et al., 1975). Among a small group of recruits who had not begun basic training (n = 246), about 3 percent had H-2 hearing or worse. In a group of recruits who had completed their basic training (n = 255), 6 percent had H-2 hearing or worse. More recent data from the DOEHRS hearing conservation (DOEHRS-HC) database showed that from 1982 through 2003, only about 8 to 10 percent of Army personnel in the hearing conservation program were classified as H-2 or worse (U.S. Army Center for Health Promotion and Preventive Medicine, 2004b). The data suggest lower rates of hearing loss over the past 20 years compared to the mid-1970s, but the two populations are not necessarily comparable. For Air Force personnel in the hearing conservation program for the period 2000–2003, about 10 to 12 percent of those in the hearing conservation program were classified as H-2 hearing or worse (Air Force Hearing Conservation Registry, 2004a).

Given that the H-1 classification permits moderate-to-profound high-frequency hearing loss, the percentages of personnel who do not meet the H-1 standard most likely underestimate the prevalence of hearing loss at high frequencies. Such losses are consistent with noise exposure, but from the H classification system alone, it is not possible to determine their etiology. In addition, these overall percentages do not account for any differences in the underlying age distributions or noise-exposure histories of the populations under consideration.

Threshold Shifts

The committee also examined reports on cases of STS and permanent threshold shift (PTS) provided by the hearing conservation programs of the Army, Navy, Air Force, and Marine Corps. Although the definition of STS used by the services has varied over time, the purpose of the measure is to

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

identify for follow-up individuals who demonstrate a clinically significant change in hearing thresholds relative to an earlier baseline (reference) measurement. An STS should be followed up with up to two additional measurements of hearing thresholds after a prescribed period of quiet. If the STS remains, or if the individual is not retested, the STS is classified as a PTS and a new reference is established to be used in subsequent assessments of STS.

Reports of cases of STS are available for thousands of military personnel enrolled in the services’ hearing conservation programs, in some cases across several years. Data were available from the Army for 1983–2003 (U.S. Army Center for Health Promotion and Preventive Medicine, 2004c), from the Air Force for 1989–2004 (Air Force Hearing Conservation Registry, 2004c), and for the Navy and Marine Corps for 1999–2004 (Navy Environmental Health Center, 2004a). During this period, definitions of STS changed in 1987 and 1999. For example, for the period up to 1987, the Army defined STS as a change of at least 20 dB at 1000, 2000, 3000, or 4000 Hz or a change greater than 10 dB in the average hearing loss at 2000, 3000, and 4000 Hz in either ear. No age corrections were applied for the comparison with the reference thresholds. From 1987 to 1999, however, the Army used the same criteria, except that age corrections were applied. Applying age corrections would be expected to reduce the incidence of STS (and PTS), all else being equal, but a steady increase in reported STS occurred from 1987 through 1999. As of 1999, the Army (and the other branches of the military) eliminated age correction and the 20-dB individual-frequency criterion was reduced to 15 dB.

The data from the Army show that roughly 6 to 8 percent of the audiograms obtained from military personnel in the hearing conservation program demonstrated positive STS each year from 1983 to 1987. The percentage of tested personnel who were found to have an STS has progressed steadily since 1987, and by 1999, the STS percentage had reached about 18 percent. It has remained at about that level since 1999. Since then, the STS percentage for the Navy and Marine Corps hearing conservation programs declined from levels of about 22–25 percent to levels of about 15–18 percent. In general, STS percentages have been lowest for the Air Force hearing conservation program, ranging from about 7 to 13 percent over the 15-year period for which data are available. Reports of PTS have generally followed similar patterns, with the Air Force again having the lowest percentages.

Other STS data have also been reported. For example, the STS percentages for the Air Force hearing conservation program started at about 23 percent in 1975 and declined steadily to about 14 percent in 1979 (Department of the Air Force, 1980). However, a more complex definition of STS was employed in which the criterion amount of threshold change consid-

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

ered to be significant varied with the severity of hearing loss demonstrated in the reference thresholds.

Wolgemuth et al. (1995) reported on STS incidence for a large sample (n = 12,492) of Navy personnel in the hearing conservation program of the Atlantic Fleet from 1987 to 1990. An overall STS incidence of 29 percent was reported using STS definitions equivalent to those used by the Army. This level is about three times greater than that for the Army from the same 1987–1990 period. It is not clear, however, whether age corrections were applied to the Navy data, as was the case for the Army. If not, this could account for some of the difference in STS incidence. In addition, the Army data are provided only for positive STS cases, and it is unclear if this was also true for the data from the Navy.

A recent analysis conducted for the Navy (Shaw and Trost, 2005) used STS as an outcome variable to examine the effect of noise on hearing of Navy enlisted personnel (n ~ 251,000) during the period 1979–2004. STS was established based on the difference between a sailor’s earliest and latest hearing tests under the hearing conservation program. It was defined as an average change of 10 dB or more in thresholds at 2000, 3000, and 4000 Hz in either ear. In the absence of direct data on individual noise exposures, the analysis used data on occupational specialties and time spent assigned to various types of ships or other assignments to assess the combined effects on the risk of STS. The statistical analysis controlled for age, race, and gender.

Overall, 11 percent of the study population was found to have an STS, which is about half the annual incidence values reported in DOEHRS-HC for the Navy’s hearing conservation program from 1999 to 2004. Shaw and Trost (2005) identified some variables that can influence the amount of STS observed. They reported that the time assigned to surface warships (e.g., aircraft carriers, battleships, destroyers, amphibious ships), for example, had a greater impact on STS than time assigned to other surface ships, certain submarine duties, or shore duties. Assignments to submarine engine rooms and Air Wings produced no greater risk than shore assignments, possibly because of ready access to and use of hearing protection. The probability of an STS reached 0.46 if the individual spent the entire study assigned to a surface war ship, a level significantly higher than the probability of 0.27 for individuals assigned entirely to shore duty.

The foregoing review of STS data suggests that a substantial number of individuals may be experiencing declines of at least 10 dB in their hearing while in the military. It is not possible, however, to discern the causes underlying such changes (especially in the absence of age corrections), the time over which such shifts occurred (e.g., 1 year or 20 years), or the resulting degree of hearing loss associated with the shift (a shift from 0 to 15 dB HL, both levels reflecting normal hearing, or a shift from 20 to 35 dB

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

HL, from normal to mild hearing loss). Moreover, hearing thresholds at 6000 Hz are not considered in any definition of STS, yet the average data indicate that hearing loss among military personnel is likely to be greatest at this frequency.

These data must be interpreted with considerable caution for other reasons as well. The DOEHRS-HC system is still experiencing difficulty in collecting data from each service. Percentages of individuals in the hearing conservation programs for whom reports of annual audiograms have been submitted to the DOEHRS-HC system have varied but have averaged only about 45 percent for the Army since 1998 and 55 percent for the Air Force since 2000 (Air Force Hearing Conservation Registry, 2004b; U.S. Army Center for Health Promotion and Preventive Medicine, 2004a; also see Chapter 5). Similar problems have been described for the Army data for the years preceding the implementation of the DOEHRS-HC system (Ohlin, 2004b). Moreover, the apparent incidence of PTS reflects not only threshold shifts that persist after retesting, but any cases in which the follow-up testing was not done, likely leading to an overestimate of the true incidence of PTS.

EPIDEMIOLOGICAL STUDIES OF NOISE-INDUCED HEARING LOSS IN INDIVIDUALS WITH PRIOR MILITARY SERVICE

The Vietnam Experience Study, conducted by the Centers for Disease Control (CDC, 1988a,b), included examination of hearing status among a random sample of male veterans who had enlisted in the U.S. Army during the period 1965 through 1971. The hearing levels of the men who had served in Vietnam (n = 2,490) were compared with those of men who had not served in Vietnam (n = 1,972). The mean age of the study participants in each group was 37 years. High-frequency hearing loss was defined as an average threshold at 3000, 4000, and 6000 Hz ≥ 51 dB HL. Individual cases were classified as positive or negative with regard to the presence of high-frequency hearing loss based on this definition. Six covariates were included in the logistic regression analysis that was performed on these data: age at enlistment, race, year of enlistment, enlistment status (volunteer versus draftee), score on a general technical test, primary military occupation, and preservice hearing loss.

Of the veterans who served in Vietnam, 18 percent met the hearing-loss criterion for their left ears, compared with 13 percent of those who were not in Vietnam. Smaller percentages had qualifying hearing losses in their right ears or in both ears. Overall, the Vietnam veterans were 40 percent more likely to have high-frequency hearing loss in either ear alone or both ears than the veterans who had not served in Vietnam. Follow-up analyses indicated that this was driven primarily by those Vietnam veterans with

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

military tactical occupational specialties (e.g., infantry, artillery, armor), who were 2.5 times more likely than non-Vietnam veterans to have high-frequency hearing loss. Those veterans who served in Vietnam in nontactical occupational specialties were not at significantly greater risk for hearing loss than otherwise similar veterans who did not serve in Vietnam.

These results illustrate the importance of exposure conditions, including combat, for identifying an elevated risk for hearing loss among Vietnam veterans. These data reflect hearing thresholds 15–20 years after service in Vietnam and include any effects of subsequent noise exposures or any selection effects that may have resulted in differences between the groups in subsequent noise exposure or survival.

Noe et al. (2002) compared hearing thresholds among veterans and nonveterans using data from a community-based cohort study of older adults in Beaver Dam, Wisconsin. The average age for both groups was approximately 65 years. Hearing loss was defined as a pure-tone average hearing threshold of 25 dB HL or greater for 500, 1000, 2000, and 4000 Hz, and cases were then classified as being either positive or negative with regard to hearing loss. Covariates included in the subsequent logistic-regression analysis included age, longest held occupation, history of head injury, and smoking. Veterans (n = 999) were not found to be at greater risk for hearing loss than nonveterans (n = 588). In addition, mean hearing thresholds for the two groups were similar at all measured frequencies from 500 through 8000 Hz. This analysis does not attempt to address differences related to noise exposure, only differences associated with prior military service. Nonveterans, too, are subject to occupational noise exposure, and in this study prior military service as such is not associated with an increased risk of hearing loss in a population of older adults.

FINDINGS

In the more than 60 years since the U.S. entrance into World War II, over 25 million people have served in the U.S. armed forces. Their experiences, in five different services and at least five major conflicts, as well as peacetime eras, have exposed many to loud noise. These noise exposures are likely to have varied widely, even within similar occupational specialties and eras. Data and analyses to document and quantify noise exposures of military personnel during this period, as well as to document and quantify their hearing thresholds and permanent changes in those thresholds over the course of military service, are not available.

The committee found only a limited number of studies on which to base its findings, and those studies were primarily for the period since 1970. Among these were cross-sectional studies showing patterns of hearing loss consistent with noise exposure, but no longitudinal studies that could pro-

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

vide reliable data on changes in individuals’ hearing thresholds over the course of military service.

The available studies were not designed to be representative of a service as a whole and only rarely of a particular occupational group. Together, these factors made it impossible to generalize findings from these studies to broader populations of military service members or veterans or to personnel serving in other time periods. Furthermore, the variability of individual responses to noise exposure precludes using the average hearing thresholds reported for groups of study participants to estimate the hearing loss of individuals.


FINDING: The evidence is sufficient to conclude that certain military personnel from World War II to the present have exhibited hearing thresholds while in the military that are typical of noise-induced hearing loss.


FINDING: The evidence is not sufficient to reach conclusions regarding the number or proportion of service members, overall or in specific occupational groups or eras since World War II, who have experienced noise-induced hearing loss while in the military.


FINDING: The evidence is not sufficient to determine the probability of acquiring noise-induced hearing loss associated with service in the military, or in specific branches of the military, for a given individual. The probability of acquiring noise-induced hearing loss can only be determined precisely with well-controlled, longitudinal epidemiological studies.


FINDING: The evidence is sufficient to conclude that, in the absence of audiograms obtained at the beginning and end of military service, it is difficult or impossible to determine with certainty how much of a specific individual’s hearing loss was acquired during military service.

REFERENCES

Air Force Hearing Conservation Registry. 2004a. DOEHRS Data Repository: Air Force Hearing Profile by Pay Grade, 2000–2004. Data provided to the Institute of Medicine Committee on Noise-Induced Hearing Loss and Tinnitus Associated with Military Service from World War II to the Present, Washington, DC.

Air Force Hearing Conservation Registry. 2004b. DOEHRS Data Repository: Hearing Conservation Compliance Report, 2000–2003. Data provided to the Institute of Medicine Committee on Noise-Induced Hearing Loss and Tinnitus Associated with Military Service from World War II to the Present, Washington, DC.

Air Force Hearing Conservation Registry. 2004c. DOEHRS Data Repository: Positive Significant Threshold Shift, 1999–2004. Data provided to the Institute of Medicine Committee on Noise-Induced Hearing Loss and Tinnitus Associated with Military Service from World War II to the Present, Washington, DC.

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

AMSA (Army Medical Surveillance Activity). 1998. Tri-Service Reportable Events: Guidelines and Case Definitions. [Online]. Available: http://amsa.army.mil/TriServiceRE/Jul98TriServREGuide.pdf [accessed April 24, 2005].

AMSARA (Accession Medical Standards Analysis and Research Activity). 2002. Annual Report 2002. Washington, DC: Walter Reed Army Institute of Research.

ANSI (American National Standards Institute). 1969. Specification for Audiometers (ANSI S3.6-1969). New York: Acoustical Society of America.

ANSI. 1996. ANSI S3.44 Determination of Occupational Noise Exposure and Estimation of Noise-Induced Hearing Impairment. New York: Acoustical Society of America.

ASA (American Standards Association). 1951. American Standard Specification for Audiometers for General Diagnostic Purposes. Pub. No. Z24.5-1951. New York: ASA.


Bohnker BK, Page JC, Rovig G, Betts LS, Muller JG, Sack DM. 2002. U.S. Navy and Marine Corps Hearing Conservation Program, 1995–1999: Mean hearing thresholds for enlisted personnel by gender and age groups. Military Medicine 167(2):132–135.


Carmichael JC. 1955. Noise health hazards in the Air Force. Public Health Reports 70(12):1251–1256.

CDC (Centers for Disease Control). 1988a. Health status of Vietnam veterans. I. Psychosocial characteristics. The Centers for Disease Control Vietnam Experience Study. Journal of the American Medical Association 259(18):2701–2707.

CDC. 1988b. Health status of Vietnam veterans. II. Physical health. The Centers for Disease Control Vietnam Experience Study. Journal of the American Medical Association 259(18):2708–2714.

CHABA (National Academy of Sciences–National Research Council Committee on Hearing, Bioacoustics, and Biomechanics). 1968. Proposed Damage-Risk Criterion for Impulse Noise (Gunfire). Report of Working Group 57 (Ward WD, ed.). Washington, DC: National Academy of Sciences.

Chandler D (Walter Reed Army Medical Center). 2005. RE: Seek your help with technical review. E-mail to L. Joellenbeck, Institute of Medicine, June 20.

Chandler DW, Fletcher JL. 1983. Hearing levels in U.S. Army engineers. Journal of Audiology Research 23(1):23–32.

Crowder L (Navy Environmental Health Center). 2005. RE: Request technical review of draft report sections. E-mail to L. Joellenbeck, Institute of Medicine, June 9.


Department of the Air Force. 1980. Hearing Conservation Program Status Report: January– June 1980. Washington, DC: Department of the Air Force.

Department of the Air Force. 1982. AF Regulation 161-35: Hazardous Noise Exposure. Washington, DC: Department of the Air Force.

Department of the Air Force. 1994. AFOSH Standard 48-19: Hazardous Noise Program. Washington, DC: Department of the Air Force.

Department of the Army. 2003. Section 3-30: Hearing conservation program. In: TRADOC Regulation 350-6: Training: Enlisted Initial Entry Training (IET) Policies and Administration. Washington, DC: Department of the Army.

Department of the Navy. 1983. Chapter 18: Hearing conservation and noise abatement. In: OPNAVINST 5100.23B: Navy Occupational Safety and Health Program Manual. Washington, DC: Department of the Navy.

Department of Veterans Affairs. 2005. America’s Wars. [Online]. Available: http://www1.va.gov/opa/fact/amwars.html [accessed May 2005].

DoD (Department of Defense). 1978. Department of Defense Instruction 6055.3: Hearing Conservation. Washington, DC: Department of Defense.

DoD. 1987. Department of Defense Instruction 6055.12: Department of Defense Hearing Conservation Program. Washington, DC: Department of Defense.

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

DoD. 1996. Department of Defense Instruction 6055.12: DoD Hearing Conservation Pro-gram. Washington, DC: Department of Defense.

DoD. 1997. MIL-STD-1474D: Department of Defense Design Criteria Standard—Noise Lim-its. Washington, DC: Department of Defense.

DoD. 1998. Department of Defense Instruction 6055.1: DoD Safety and Occupational Health (SOH) Program. Washington, DC: Department of Defense.

DoD. 2004. Department of Defense Instruction 6055.12: DoD Hearing Conservation Pro-gram. Washington, DC: Department of Defense.


Fairman TM, Johnson DL. 1979. Noise dosimeter measurements in the Air Force. Aviation, Space, and Environmental Medicine 50(11):1150–1157.


Gasaway DC. 1986. Noise levels in cockpits of aircraft during normal cruise and considerations of auditory risk. Aviation, Space, and Environmental Medicine 57(2):103–112.

Gasaway DC. 1988. Occupational hearing conservation in the military. In: Lipscomb DM, ed. [Jacobson JT, advisory ed.]. Hearing Conservation in Industry, Schools, and the Military. Boston: Little, Brown. Pp. 243–262.

Gasaway DC. 2002. Donald C. Gasaway’s Aircraft Noise Compendia. Washington, DC: Department of the Air Force.

Glorig A. 1952. Field investigations on military personnel as regards sound. In: University of Michigan School of Public Health, Institute of Industrial Health. The Acoustical Spec-trum. Sound—Wanted and Unwanted. Ann Arbor: University of Michigan Press. Pp. 99–106.

Glorig A, Roberts J. 1965. Hearing Levels of Adults by Age and Sex, United States, 1960–1962. Vital and Health Statistics. Series 11, No. 11. Washington, DC: Department of Health, Education, and Welfare.

Glorig A, Wheeler D, Quiggle R, Grings W, Summerfield A. 1957. 1954 Wisconsin State Fair Hearing Survey. Statistical Treatment of Clinical and Audiometric Data. Los Angeles: American Academy of Ophthalmology and Otolaryngology.

Goldenberg RA. 1977. Hearing loss in the Marine Corps. Transactions—American Academy of Ophthalmology and Otolaryngology 84(6):991–996.

Gravendeel DW, Plomp R. 1959. The relation between permanent and temporary noise dips. American Medical Association-The Archives of Otolaryngology 69(6):714–719.


Henselman LW, Henderson D, Shadoan J, Subramaniam M, Saunders S, Ohlin D. 1995. Effects of noise exposure, race, and years of service on hearing in U.S. Army soldiers. Ear and Hearing 16(4):382–391.


ISO (International Organization for Standardization). 1990. ISO 1999: Acoustics—Determi-nation of Occupational Noise Exposure and Estimation of Noise-Induced Hearing Im-pairment. Geneva, Switzerland: ISO.


Johnson DL, Nixon CW. 1974. Simplified methods for estimating hearing protector perfor-mance. Sound and Vibration 8(6):20–27.

Jordan DT Jr, Jones CM. 1983. Noise Exposure Study of Reese AFB Personnel Working on the Flightline in Selected Adjacent Shops. OEHL 83-220EH165HNA. Brooks Air Force Base, TX: U.S. Air Force Occupational and Environmental Health Laboratory.


Kardous CA, Willson RD. 2004. Limitations of using dosimeters in impulse noise environ-ments. Journal of Occupational and Environmental Hygiene 1(7):456–462.


Marshall L, Carpenter S. 1988. Hearing Levels of 416 Sonar Technicians. NSMRL Report No. 1123. Groton, CT: Naval Submarine Medical Research Laboratory.

McConnell W. 2004. Hearing Conservation in the Coast Guard. Presentation to the Insti-tute of Medicine Committee on Noise-Induced Hearing Loss and Tinnitus Associated with Military Service from World War II to the Present, Meeting I. Washington, DC. May 12.

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

McConnell W (U.S. Coast Guard). 2005. Technical Review of Draft Section on Coast Guard. Comments provided to the Institute of Medicine Committee on Noise-Induced Hearing Loss and Tinnitus Associated with Military Service from World War II to the Present, Washington, DC.


Navy Environmental Health Center. 2004a. DOEHRS Data Repository: Positive Significant Threshold Shift, 1999–2004. Data provided to the Institute of Medicine Committee on Noise-Induced Hearing Loss and Tinnitus Associated with Military Service from World War II to the Present, Washington, DC.

Navy Environmental Health Center. 2004b. Navy Medical Department Hearing Conservation Program Procedures. NECH-TM 6260.51.99-2. Portsmouth, VA: U.S. Navy, Bureau of Medicine and Surgery.

Nixon CW. 1998. A Glimpse of History: The Origin of Hearing Conservation Was in the Military? Wright-Patterson Air Force Base, OH: Air Force Research Laboratory.

Noe CM, Cruickshanks KJ, Nondahl D, Wiley TL, Wilson RH. 2002. Prevalence of Hearing Loss Among the Veteran Population in the Beaver Dam (WI) Cohort (abstract). Third Rehabilitation Research and Development Conference, Arlington, VA. February 10–12.


Ohlin D. 1992. 15 Years Revisited: The Prevalence of Hearing Loss Among Selected U.S. Army Branches. Hearing Conservation Special Study No. 51-01-PM82-93. Aberdeen Proving Ground, MD: U.S. Army Environmental Hygiene Agency.

Ohlin D. 2004a. DoD and Army Data and Databases. Presentation to the Institute of Medicine Committee on Noise-Induced Hearing Loss and Tinnitus Associated with Military Service from World War II to the Present, Meeting II. Washington, DC. July 19.

Ohlin D (U.S. Army Center for Health Promotion and Preventive Medicine). 2004b. Requested DOEHRS-HC Reports for Committee on Noise-Induced Hearing Loss and Tinnitus Associated with Military Service. E-mail to J. Durch, Institute of Medicine, July 23.

Ohlin D (U.S. Army Center for Health Promotion and Preventive Medicine). 2005. RE: Seek Help with STS Definitions. E-mail to L. Joellenbeck, Institute of Medicine, March 25.


Peters LJ, Ford H. 1983. Extent of Hearing Loss Among Army Aviators at Fort Rucker, Alabama. USAAMRL 83-12. Fort Rucker, AL: U.S. Army Aeromedical Research Laboratory.


Ritter DC, Perkins JL. 2001. Noise-induced hearing loss among U.S. Air Force cryptolinguists. Aviation, Space, and Environmental Medicine 72(6):546–552.

Robertson RM, Maxwell DW, Williams CE. 1978a. The Landing Signal Officer: Auditory Aspects. NAMRL-1255. Pensacola, FL: Naval Aerospace Medical Research Laboratory.

Robertson RM, Page JC, Williams CE. 1978b. The Prevalence of Hearing Loss Among Selected Navy Enlisted Personnel. NAMRL-1251. Pensacola, FL: Naval Aerospace Medical Research Laboratory.

Robertson RM, Greene JW, Williams CE, Maxwell DW. 1990. Noise Exposure of Naval Communication Station Radio Operators: A Field Study. NAMRL Technical Memorandum 90-1. Pensacola, FL: Naval Aerospace Medical Research Laboratory.

Royster LH, Thomas WG, Royster JD, Lilley D. 1978. Potential hearing compensation cost by race and sex. Journal of Occupational Medicine 20(12):801–806.


Shaw GB, Trost RP. 2005. Statistical Analysis of Hearing Loss Among Navy Personnel. CRM D0011228.A2. Alexandria, VA: CNA.

Solomon LN, Fletcher JL. 1958. Survey of hearing losses among armor personnel. Journal of Speech and Hearing Disorders 1(4):350–358.

Sutherland HC, Gasaway DC. 1976. Hearing Levels of Noise-Exposed U.S. Air Force Personnel Compared to Those in the Total U.S. Population. Report SAM-TR-76-27. Brooks Air Force Base, TX: US Air Force School of Aerospace Medicine.

Sutherland HC, Gasaway DC. 1978. Current Hearing Threshold Levels for Noise-Exposed U.S. Air Force Personnel. One Year’s Reportings. Report SAM-TR-78-39. Brooks Air Force Base, TX: U.S. Air Force School of Aerospace Medicine.

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×

Thomas JW. 1995. The Application of Audiometric Data Base Analysis to Selected Air Force Bases. Master’s thesis, University of North Carolina, Chapel Hill.


U.S. Army Center for Health Promotion and Preventive Medicine. 1999. Technical Guide 181: Noise Dosimetry and Risk Assessment. Aberdeen Proving Ground, MD: U.S. Army Center for Health Promotion and Preventive Medicine.

U.S. Army Center for Health Promotion and Preventive Medicine. 2004a. DOEHRS Data Repository: Army Hearing Conservation Program Compliance Reports, 1988–2003. Data provided to the Institute of Medicine Committee on Noise-Induced Hearing Loss and Tinnitus Associated with Military Service from World War II to the Present, Washington, DC.

U.S. Army Center for Health Promotion and Preventive Medicine. 2004b. DOEHRS Data Repository: Army Hearing Profile Reports, 1975–2003. Data provided to the Institute of Medicine Committee on Noise-Induced Hearing Loss and Tinnitus Associated with Military Service from World War II to the Present, Washington, DC.

U.S. Army Center for Health Promotion and Preventive Medicine. 2004c. DOEHRS Data Repository: Hearing Conservation Program Positive STS Report, 1983–2003. Data provided to the Institute of Medicine Committee on Noise-Induced Hearing Loss and Tinnitus Associated with Military Service from World War II to the Present, Washington, DC.

U.S. Army Center for Health Promotion and Preventive Medicine. 2004d. Noise Levels of Common Army Equipment. [Online]. Available: http://chppm-www.apgea.army.mil/hcp/NoiseLevelsPrint.htm [accessed April 21, 2004].


Walden BE, Worthington DW, McCurdy HW. 1971. The Extent of Hearing Loss in the Army: A Survey Report. Washington, DC: Walter Reed Army Medical Center.

Walden BE, Prosek RA, Worthington DW. 1975. The Prevalence of Hearing Loss Within Selected U.S. Army Branches. Washington, DC: Walter Reed Army Medical Center.

Weisman W (U.S. Air Force Surgeon General’s Office). 2005. Technical Review of Draft Section on Air Force Noise Measurements and Dosimetry. Comments provided to the Institute of Medicine Committee on Noise-Induced Hearing Loss and Tinnitus Associated with Military Service from World War II to the Present, Washington, DC.

Wolgemuth KS, Luttrell WE, Kamhi AG, Wark DJ. 1995. The effectiveness of the Navy’s hearing conservation program. Military Medicine 160(5):219–222.


Yankaskas K. 2001. Landing on the Roof: Flight Operation Noise. Presentation at the International Military Noise Conference, Baltimore, MD. April 25.

Yankaskas K. 2004. Shipboard Noise and Hearing Conservation Issues. Presentation to the Institute of Medicine Committee on Noise-Induced Hearing Loss and Tinnitus Associated with Military Service from World War II to the Present, Meeting IV, Washington, DC. December 7.

Yankaskas KD, Shaw MF. 1999. Landing on the roof: CVN noise. Naval Engineers Journal 111(4):23–34.

Yarington CT. 1968. Military noise induced hearing loss: Problems in conservation programs. Laryngoscope 78(4):685–692.

Ylikoski ME, Ylikoski JS. 1994. Hearing loss and handicap of professional soldiers exposed to gunfire noise. Scandinavian Journal of Work, Environment & Health 20(2):93–100.

Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 72
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 73
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 74
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 75
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 76
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 77
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 78
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 79
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 80
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 81
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 82
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 83
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 84
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 85
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 86
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 87
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 88
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 89
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 90
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 91
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 92
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 93
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 94
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 95
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 96
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 97
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 98
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 99
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 100
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 101
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 102
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 103
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 104
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 105
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 106
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 107
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 108
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 109
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 110
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 111
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 112
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 113
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 114
Suggested Citation:"3 Noise and Noise-Induced Hearing Loss in the Military." Institute of Medicine. 2006. Noise and Military Service: Implications for Hearing Loss and Tinnitus. Washington, DC: The National Academies Press. doi: 10.17226/11443.
×
Page 115
Next: 4 Tinnitus »
Noise and Military Service: Implications for Hearing Loss and Tinnitus Get This Book
×
Buy Paperback | $65.00
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

The Institute of Medicine carried out a study mandated by Congress and sponsored by the Department of Veterans Affairs to provide an assessment of several issues related to noise-induced hearing loss and tinnitus associated with service in the Armed Forces since World War II. The resulting book, Noise and Military Service: Implications for Hearing Loss and Tinnitus, presents findings on the presence of hazardous noise in military settings, levels of noise exposure necessary to cause hearing loss or tinnitus, risk factors for noise-induced hearing loss and tinnitus, the timing of the effects of noise exposure on hearing, and the adequacy of military hearing conservation programs and audiometric testing. The book stresses the importance of conducting hearing tests (audiograms) at the beginning and end of military service for all military personnel and recommends several steps aimed at improving the military services’ prevention of and surveillance for hearing loss and tinnitus. The book also identifies research needs, emphasizing topics specifically related to military service.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    Switch between the Original Pages, where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text.

    « Back Next »
  6. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  7. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  8. ×

    View our suggested citation for this chapter.

    « Back Next »
  9. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!