Noise and Military Service Implications for Hearing Loss and Tinnitus (2006) / Chapter Skim
Currently Skimming:
3 Noise and Noise-Induced Hearing Loss in the Military
3 Noise and Noise-Induced Hearing Loss in the Military
Pages 72-115
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 72... ...
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)
|
From page 73... ...
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)
|
From page 74... ...
. DoD also has established design standards for noise levels of new materiel designed or purchased for the military services.
|
From page 75... ...
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.
|
From page 76... ...
. Coast Guard Coast Guard noise surveys were part of the Coast Guard hearing conservation program by the late 1960s and early 1970s (McConnell, 2004)
|
From page 77... ...
. 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)
|
From page 78... ...
78 dBA Sound Level 128 117 120 109 81 111 103 108 dB Level Level (±10)
|
From page 79... ...
79 continued Level 78 84 94 85 88 92 98 85 Sound dBA < < 100 (sec Duration event)
|
From page 80... ...
80 Level 85 85 93 Sound dBA < < 106 109 114 118 103 108 114 117 8591 8592 idle (mph)
|
From page 81... ...
Preventive propellant multipurpose HMMWV HMMWV HMMWV position 8 and position hearing from from from position M203 charge Condition Fired Fired Fired Open Enclosed Fighting At Firing integral high-mobility Promotion 3 with Health Mod HMMWV, for helmets 19, 19 wear Center Model M9 M16A2 M249 M60 M2 MK M26 M3 M72A3 Ml M198 operations. crews Army air by U.S.
|
From page 82... ...
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)
|
From page 83... ...
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.
|
From page 84... ...
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.
|
From page 85... ...
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)
|
From page 86... ...
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)
|
From page 87... ...
NOISE AND NOISE-INDUCED HEARING LOSS IN THE MILITARY 87 TABLE 3-2 Time Line of Major Conflicts, Milestones in Hearing Conservation Programs, and Hearing Protection Devices Hearing Conservation Year Major Conflicts Milestones Hearing Protection Available 1941 World War II Cotton, fingers, or no begins protection 1945 World War II Some early hearing protection ends available: V-51R, early ear muffs 1948 Air Force issues first regulation concerning hazardous noise 1950 Korean War 1950s: Introduction and in begins creasing use of pure-tone audiometry 1953 Korean War ends 1956 Air Force introduces first of services' hearing conservation programs 1960 Pure-tone audiometry 1960s: V-51R, triple-flange replaces whisper test earplugs, improved earmuffs for screening military applicants 1964 Vietnam War begins 1970 First Navy comprehensive 1970s: Same earplugs and ear hearing conservation muffs, new foam earplugs, program helmets with noise Air Force begins automated attenuation introduced handling and storage of audiometric monitoring data (late 1974) 1975 Vietnam War ends 1978 DoD Instruction establishing hearing conservation programs 1980 First comprehensive Army 1980s: Conventional earplugs hearing conservation and muffs same as 1960s and program 1970s; some tanker helmets Army begins data reposi- introduced with active noise tory for audiometric reduction (ANR)
|
From page 88... ...
begins 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.
|
From page 89... ...
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.
|
From page 90... ...
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)
|
From page 91... ...
were from audiometric testing done for the hearing conservation program in 19751976. The Navy data were reported by length of service, whereas the Air Force report used age.
|
From page 92... ...
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.
|
From page 93... ...
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 1824 years, in the unscreened data were comparable to those of small groups of Army (n = 246)
|
From page 94... ...
Average thresholds were lower at every age compared with the 1970s data, but exceeded the unscreened reference levels by 35 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)
|
From page 95... ...
and aviators (x) in the early 1980s; and enlisted men from the infantry, armor, and artillery enrolled in the hearing conservation program in 1989 ( )
|
From page 96... ...
. In more recent data for enlisted men in the Navy's hearing conservation program
|
From page 97... ...
in the 1970s ( ) and for both ears for enlisted Marine Corps men in the hearing conservation program in 19951999 ()
|
From page 98... ...
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)
|
From page 99... ...
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.
|
From page 100... ...
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.
|
From page 101... ...
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)
|
From page 103... ...
103 enter 1975 (c 4554 in to 4000 (top) program years column)
|
From page 104... ...
, 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)
|
From page 105... ...
, 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.
|
From page 106... ...
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.
|
From page 107... ...
Since then, the STS percentage for the Navy and Marine Corps hearing conservation programs declined from levels of about 2225 percent to levels of about 1518 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.
|
From page 108... ...
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.
|
From page 109... ...
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)
|
From page 110... ...
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.
|
From page 111... ...
Data provided to the Institute of Medicine Com mittee 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.
|
From page 112... ...
U.S. Navy and Marine Corps Hearing Conservation Program, 19951999: Mean hearing thresholds for en listed personnel by gender and age groups.
|
From page 113... ...
1988. Occupational hearing conservation in the military.
|
From page 114... ...
Army Branches. Hearing Conservation Special Study No.
|
From page 115... ...
2004a. DOEHRS Data Repository: Army Hearing Conservation Program Compliance Reports, 19882003.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.