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From page 41...
... 41 C H A P T E R 4 4.1 Aircraft Flyovers The aircraft flyover test is used in a number of sound insulation programs. This method simultaneously measures the exterior free-field incident sound of flyovers and the diffuse sound field in the test room within the structure.
From page 42...
... 42 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs 4.1.1 Measurement Procedures Aircraft flyover measurements are made using a pair of synchronized digital programmable SLMs. One is located outside in the free field away from reflecting surfaces and extraneous noise sources; the other is located in the room to be measured for NLR, locating it away from the impinging façade and away from locations amplifying room acoustic effects.
From page 43...
... Findings and Applications 43 one microphone flush with the ground and one microphone 2 m (6 ft.) above the ground.
From page 44...
... 44 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs 4.1.2 Data Analyses The example results of the flyover measurement procedure above are shown in Table 4-1. This is from a measurement for the living room of test subject San Diego #1.
From page 45...
... Findings and Applications 45 A general rule of thumb is to measure about 25 flyover events to obtain a valid assessment of the NLR to within 0.5 dB. This varies with each individual measurement site.
From page 46...
... 46 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs of various variances from the mean are encountered. That is, the chronology of the events affects the analysis.
From page 47...
... Findings and Applications 47 44 27.4 0.9 28.1 0.42 ± 0.13 43 29.1 0.8 28.1 0.42 ± 0.12 42 29.0 0.7 28.1 0.41 ± 0.12 41 27.6 0.7 28.1 0.38 ± 0.12 40 27.6 0.7 28.1 0.36 ± 0.11 39 27.6 0.7 28.1 0.35 ± 0.11 38 28.9 0.6 28.1 0.35 ± 0.11 37 27.7 0.6 28.1 0.34 ± 0.11 36 27.7 0.6 28.1 0.32 ± 0.10 35 27.7 0.6 28.1 0.32 ± 0.11 34 27.7 0.6 28.1 0.32 ± 0.11 33 28.8 0.5 28.1 0.31 ± 0.11 32 27.8 0.5 28.1 0.31 ± 0.11 31 27.8 0.5 28.1 0.29 ± 0.10 30 27.8 0.5 28.1 0.29 ± 0.10 29 27.8 0.5 28.1 0.29 ± 0.10 28 27.8 0.5 28.1 0.29 ± 0.11 27 27.8 0.5 28.2 0.28 ± 0.11 26 27.8 0.5 28.2 0.28 ± 0.11 25 27.8 0.5 28.2 0.28 ± 0.11 24 27.8 0.5 28.2 0.27 ± 0.11 23 28.7 0.4 28.2 0.26 ± 0.11 22 28.7 0.4 28.2 0.25 ± 0.11 21 27.9 0.4 28.2 0.24 ± 0.10 20 27.9 0.4 28.2 0.22 ± 0.09 19 27.9 0.4 28.2 0.21 ± 0.10 18 28.0 0.3 28.2 0.21 ± 0.09 17 28.0 0.3 28.2 0.20 ± 0.09 16 28.0 0.3 28.2 0.19 ± 0.09 15 28.0 0.3 28.3 0.19 ± 0.10 14 28.0 0.3 28.3 0.18 ± 0.10 13 28.0 0.3 28.3 0.17 ± 0.09 12 28.0 0.3 28.3 0.16 ± 0.09 11 28.5 0.2 28.3 0.13 ± 0.08 San Diego #1 -- Sorted by Standard Deviaon n NLR |NLR NLRAvg| NLR AVG Std Dev 95% CI 10 28.5 0.2 28.4 0.08 ± 0.05 9 28.4 0.1 28.4 0.07 ± 0.05 8 28.4 0.1 28.3 0.05 ± 0.04 7 28.4 0.1 28.3 0.05 ± 0.04 6 28.4 0.1 28.3 0.05 ± 0.04 5 28.3 0.0 28.3 0.04 ± 0.04 4 28.3 0.0 28.3 0.00 ± 0.00 3 28.3 0.0 28.3 0.00 ± 0.00 2 28.3 0.0 28.3 0.00 ± 0.00 1 28.3 0.0 28.3 0.00 ± 0.00 Note: The 2 dB reflecon correcon has not been applied to the above data. A blank cell indicates either no event recorded at interior or no event noted by the airport monitoring system.
From page 48...
... 48 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs 4.1.3 Sources of Error: Overview Reflections: Up to 4 dB increase in sound level from ground reflections and reflections from the façade under test (if the outdoor microphone is located near the building façade)
From page 49...
... Findings and Applications 49 power settings, volume of daytime and nighttime operations, landings, etc. used to prepare the NEM.
From page 50...
... 50 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs 4.1.3.4 Non-Reverberant Sound Field Acoustical consultants have long recognized the lack of an ideal reverberant sound field in measuring rooms within homes. This problem exists with all measurement methods, but is ameliorated to some degree with the loudspeaker method where the measurement within the room is attended by manually moving the microphone to achieve a better spatial average of the sound field.
From page 51...
... Findings and Applications 51 Residence Room Arithmec Average Median Difference (Arith Median) San Diego #1 Living Room 26.3 26.3 0.0 Dining Room 28.0 28.2 -0.2 San Diego #2 Living Room 24.3 24.2 0.1Bedroom 4 20.4 20.4 0.0 San Diego #3 Living Room 23.7 24.0 -0.3Master BR 24.7 24.4 0.3 San Diego #4 Living Room 23.2 23.5 -0.3Bedroom 1 26.3 26.3 0.0 San Diego #5 Living Room 24.0 24.3 -0.3Bedroom 1 30.0 30.2 -0.2 San Diego #6 Living Room 24.9 24.9 0.0 Dining Room 27.4 27.5 -0.1 San Diego #7 Living Room 25.1 25.1 0.0 Family Room 26.5 26.8 -0.3 San Diego #8 Master BR 22.2 21.7 0.5 Dining Room 19.4 19.2 0.2 San Diego #9 Living Room 21.8 21.9 -0.1Bedroom 1 31.7 31.6 0.1 San Diego #10 Bedroom 1 17.5 17.5 0.0Bedroom 2 25.0 25.3 -0.3 Average 0.0 Table 4-4.
From page 52...
... 52 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs The long boom length of the rotating microphone required that large rooms be measured; most rooms were living rooms. The two stationary microphones were generally placed in opposite room quadrants to measure the noise environment in distinct areas.
From page 53...
... Findings and Applications 53 other measurement techniques as well. For example, an 80-dB flyover with a concentration of low frequency energy will produce a lower NLR than another 80-dB flyover with more energy concentrated in the higher frequencies.
From page 54...
... 54 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs Table 4-7 compares the computed exterior and interior SEL (an integrated measure of the total sound energy of a noise event) , values for the aircraft classes, and computes the attendant NLR values.
From page 55...
... Findings and Applications 55 • In general, the results varied little from measurement to measurement; however, there were a few outliers which warranted closer examination. • Similar to the elevated loudspeaker, the NLR decreased by approximately 1 dB when the roof and walls were measured at the exterior (rather than just the walls)
From page 56...
... 56 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs on ASTM E966-10) to account for the reverberant noise build-up at the façade, and (c)
From page 57...
... Findings and Applications 57 While the conversion utilizes standard acoustical calculations, there is no standard guidance on how to determine the reference aircraft spectrum. Many consultants involved with sound insulation programs measure multiple arrivals and departures at a given airport and then average these events to calculate the reference spectrum.
From page 58...
... 58 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs Residence Room Reference Spectrum NLR (dB) San Diego #5 Living SAN 21.3 OITC 20.7 Difference 0.6 Bedroom 1 SAN 26.3 OITC 25.0 Difference 1.3 San Diego #6 Living SAN 20.9 OITC 20.2 Difference 0.7 Dining SAN 26.4 OITC 24.9 Difference 1.5 San Diego #7 Family SAN 25.7 OITC 26.4 Difference -0.7 Difference 0.2 Living SAN 24.6 OITC 24.4 San Diego #9 Living SAN 19.4 OITC 18.8 Difference 0.6 Bedroom 1 SAN 25.6 OITC 25.0 Difference 0.6 San Diego #10 Bedroom 1 SAN 17.6 OITC 17.7 Difference -0.1 Bedroom 2 SAN 25.1 OITC 25.9 Difference -0.8 Boston #1 (storm windows closed)
From page 59...
... Findings and Applications 59 4.2.3 Repeatability At one of the test homes, the research team repeated the ground-level loudspeaker measurement with no change in loudspeaker position to determine whether the results changed from test to test. The goal was to determine whether the measurement engineer could induce significant variation in the test results.
From page 60...
... 60 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs Measured Noise Reducon (dB) Residence Room Ref.
From page 61...
... San Diego #5 Living OITC Exterior Wall and Roof 20.0 Exterior Wall Only 21.3 Difference -1.3 SAN Exterior Wall and Roof 20.6 Exterior Wall Only 22.0 Difference -1.4 San Diego #7 Family OITC Exterior Wall and Roof 24.1 Exterior Wall Only 24.7 Difference -0.6 SAN Exterior Wall and Roof 24.4 Exterior Wall Only 25.0 Difference -0.6 San Diego #8 Dining OITC Exterior Wall and Roof 18.7 Exterior Wall Only 19.7 Difference -1.0 SAN Exterior Wall and Roof 18.9 Exterior Wall Only 20.2 Difference -1.3 Master Bedroom OITC Exterior Wall and Roof 26.2 Exterior Wall Only 27.9 Difference -1.7 SAN Exterior Wall and Roof 27.5 Exterior Wall Only 29.1 Difference -1.6 Residence Room Ref. Spectrum Descrip on Noise Reduc on (dB)
From page 62...
... 62 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs façade; measurements of this diffuse field are taken along with measurements of the reverberant sound field in the room under test. Section 4.3.1 describes the measurement procedure in detail.
From page 63...
... Findings and Applications 63 (20 feet to 40 feet) above grade; a bucket/crane truck was required to accomplish this.
From page 64...
... 64 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs Study OITC 27.1 Difference -0.5 Average Difference (Flyover – OITC) 0.3 Standard Deviaon 0.6 Note: SAN and BOS reference spectrum refers to the average flyover spectrum measured at the home.
From page 65...
... Findings and Applications 65 4.3.4 Measurement of Exterior Wall and Roof vs. Exterior Wall Only Aircraft noise enters into a residence via the building envelope.
From page 66...
... 66 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs San Diego #7 Family OITC Exterior Wall and Roof 25.2 Exterior Wall Only 25.3 Difference -0.1 SAN Exterior Wall and Roof 25.4 Exterior Wall Only 25.7 Difference -0.3 Living OITC Exterior Wall and Roof 23.1 Exterior Wall Only 23.7 Difference -0.6 SAN Exterior Wall and Roof 23.4 Exterior Wall Only 24.2 Difference -0.8 San Diego #8 Dining OITC Exterior Wall and Roof 18.7 Exterior Wall Only 20.1 Difference -1.4 SAN Exterior Wall and Roof 19.2 Exterior Wall Only 20.6 Difference -1.4 Master Bedroom OITC Exterior Wall and Roof 27.1 Exterior Wall Only 28.4 Difference -1.3 SAN Exterior Wall and Roof 27.8 Exterior Wall Only 29.3 Difference -1.5 Residence Room Reference Spectrum Descripon NLR (dB) San Diego #10 Bedroom 1 OITC Exterior Wall and Roof 19.2 Exterior Wall Only 19.6 Difference -0.4 SAN Exterior Wall and Roof 18.6 Exterior Wall Only 19.1 Difference -0.5 Bedroom 2 OITC Exterior Wall and Roof 25.5 Exterior Wall Only 26.3 Difference -0.8 SAN Exterior Wall and Roof 24.9 Exterior Wall Only 25.6 Difference -0.7 Average Difference OITC -0.8 SAN -0.9 Overall -0.8 Standard Deviaon OITC 0.4 SAN 0.4 Overall 0.4 Note: SAN reference spectrum refers to the average flyover spectrum measured at the home.
From page 67...
... Findings and Applications 67 4.4 Interior Loudspeaker The interior loudspeaker measurement method was created by one acoustical consultant working on airport sound insulation programs. This method has been employed at a few airport sound insulation programs, and the research team understands that the local FAA representatives overseeing those airport sound insulation programs approved the measurement method.
From page 68...
... 68 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs corrections were then applied: (1) the subtraction of ambient noise, (2)
From page 69...
... Residence Room Reference Spectrum NLR (dB) San Diego #9 Living SAN 21.8 OITC 20.7 Difference 1.1 Bedroom 1 SAN 27.6 OITC 26.1 Difference 1.5 San Diego #10 Bedroom 1 SAN 23.7 OITC 22.7 Difference 1.0 Bedroom 2 SAN 27.0 OITC 26.6 Difference 0.4 Boston #1 (storm windows closed)
From page 70...
... 70 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs For the San Diego measurements, interior loudspeaker measurements were conducted in ten homes. In Boston, interior loudspeaker measurements were conducted in nine homes, but aircraft flyover noise spectrum was only available in four out of the nine homes.
From page 71...
... Findings and Applications 71 Table 4-16. Interior loudspeaker, comparison of wall/roof and wall only measurement.
From page 72...
... 72 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs methods are used extensively during the design process of new buildings, and the results are used to inform the architect of the required TL performance of the building envelope components (e.g., windows, doors)
From page 73...
... Findings and Applications 73 4.5.2 Acoustical Calculation Procedure In order to calculate the noise reduction of a room, there are three primary steps: (1) determine the TL of each element, (2)
From page 74...
... 74 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs 4.5.2.1 IBANA Calculation Model The first model employed was the IBANA (Insulating Buildings Against Noise from Aircraft) software, which was created by the National Research Council Canada.
From page 75...
... Findings and Applications 75 • Optional correction factors (not used) : – Air absorption.
From page 76...
... 76 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs • It is important that the field survey be very detailed so the calculations are accurate; even then, it is possible to miss flanking paths (noise leaks) that would overstate the calculated NLR.
From page 77...
... Figure 4-8. TL calculation sample spreadsheet.
From page 78...
... Average NLR (no int. spkr.)
From page 79...
... Findings and Applications 79 2. The fan was then turned on and either created a positive or negative pressure differential between the room under test and the adjacent spaces (including the outside)
From page 80...
... 80 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs measured flyover noise reduction and the noise reduction measured using an exterior loud speaker. As can also be seen in Figures 4-11 and 4-12, NLR is not correlated to the measured air infiltration.
From page 81...
... Findings and Applications 81 San Diego #6 Living San Diego #6 Dining San Diego #1 Living San Diego #8 Dining San Diego #5 Flyover N LR Ext. Spkr N LR A ir Infiltraon (cfm )
From page 82...
... 82 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs Summary: The research team conducted sound intensity measurements in five homes within the vicinity of the San Diego International Airport. Additional sound intensity measurements were conducted at a research team member's residence in Champaign, IL, for comparison purposes.
From page 83...
... Findings and Applications 83 conventional sound pressure measurements. One of the most important questions posed about sound intensity measurements is as follows: Does the flow of sound power into or out of a room and its measurement ameliorate the resonance issues that are prevalent with measurements of sound pressure (i.e., the loudspeaker or flyover method)
From page 84...
... 84 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs While this plan appears to be straightforward, to obtain the 2.5° resolution specified for this microphone assembly, one has to know the position of the microphone assembly with respect to the object or room under test, and the pitch and yaw of the microphone assembly itself. Since the goal is to gather directional data on sound power flow, it is not sufficient just to know the x, y, and z coordinates of the microphone assembly; one must also know the orientation of the assembly with respect to the source.
From page 85...
... Findings and Applications 85 Figure 4-13 shows the wand being synched to a known coordinate in the room; the wall to be measured is shown in the background. The red, green and blue colors showing the three coordinates are not actually physically in the room, but are superimposed showing the reference for the coordinate system.
From page 86...
... 86 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs Figure 4-14. Champaign home floor plan and measurement location.
From page 87...
... Findings and Applications 87 cavities in the wall were fully filled with batt insulation, and the wall was finished with a brick veneer. The windows are 43-year-old narrow line, double pane models.
From page 88...
... 88 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs Figure 4-16 shows the composite of the wall stitched together, in this case from five individual measurement episodes, one from each quadrant around the window, and one from the center of the window. To make the comparison of the results for the two flow directions easier to view, Figure 4-17 contains a side view and again shows the frontal view of the composites for each of the two directions of flow.
From page 89...
... Figure 4-16. The "stitching" together of a composite from individual measurements (the "A" in parentheses signifies that the measure is A-weighted)
From page 90...
... 90 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs In contrast, the vector plots of power flow that constitute Figure 4-20 show that the two measurement episodes taken left of the window look similar to one another, and different from the measurement episode that was only through the window. The vectors indicate flow in from the window, as expected, but then they appear to turn and split into at least two streams.
From page 91...
... Findings and Applications 91 Figure 4-18. Front view for each of the three measurements shown in Figure 4-17.
From page 92...
... 92 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs expected. The data are very complicated, neither straight through nor at a common angle; thus far the research has not been able to interpret the results.
From page 93...
... Findings and Applications 93 As an indication of the reasonableness of the 95.1 dB at the face of the wall, the measurements taken at 1.8 m (5.9 ft.) from the wall were consistently 93.9 dB (the loudspeaker at full volume is a very steady source)
From page 94...
... 94 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs episodes that make up the composite. In calculating this power, the sound intensity instrument uses only those vectors going through the area of the wall designated by the user.
From page 95...
... Findings and Applications 95 For example, for the first line in Table 4-19, the total power calculated by the sound intensity instrument and displayed on the meter is a watt level of 72.1 dB, and it is gathered with 1242 vectors. In this case, subtract 10*
From page 96...
... 96 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs As an example, consider the following two limit situations. In situation one, two measurements exactly replicate one another.
From page 97...
... Findings and Applications 97 In the results herein, there is overlap among the 5 out to in measurement episodes, in particular, episode 1 and 5 are almost equal, 41.2 and 41.1 respectively. In Figure 4.16 one can see that about 60% of episode 1 is overlapped by episode 5, and about 40% of episode 5 is overlapped by episode 1.
From page 98...
... 98 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs each of the five measurements from out to in. This table shows a rather large spread of pressure levels, just under 3 dB.
From page 99...
... Findings and Applications 99 To assess the reasonableness of the estimate of power flow into the dining room, the total room absorption calculated using the room acoustics formula above is compared with the total room absorption based on surface sizes and their finishes, furnishings, and people in the room. The two openings to the dining room are the doorway to the kitchen and the large opening to the living room.
From page 100...
... 100 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs Since there is reciprocity for both directions, the measurement from indoors to outdoors is the more promising direction. In this scenario, one creates a reverberant sound field in the room under test and determines the power flow from inside to outside by measuring the power flow out through the wall surface.
From page 101...
... Findings and Applications 101 0 to 30 cm (0 to ~1 foot) from the wall.
From page 102...
... 102 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs take the point midway between the two windows, or something close to that, and use the vertical line that goes through that point as the line dividing the wall into two sub-walls, each of which would be treated separately as above. In designating elements, the smallest permitted element dimension would be (for the current sound intensity microphone assembly)
From page 103...
... Findings and Applications 103 the user is interested in mapping the power flow through a wall or through a conformal surface that surrounds some machine. The most general analysis would divide the surfaces into logical relatively large elements.
From page 104...
... 104 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs include a pair of magnets with a hook on one of the magnets so that magnets could be on either side of drapery, or a shade, and would then support the checkerboard cord on the hook. Or, the magnet with the hook could be affixed to metal surfaces like a filing cabinet, and again supporting the checkerboard cord by the hook on the magnet.
From page 105...
... Findings and Applications 105 4.8.1 Outliers There were some rooms measured where the noise reduction results fell outside of the expected range of noise reduction and/or the flyover noise reduction varied significantly from the exterior loudspeaker noise reduction. A deeper analysis was performed for each of these rooms to determine why the results were atypical.
From page 106...
... 106 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs shielded from aircraft noise during the flyover measurements from the large overhang at the east façade and the building itself for the north façade. The living room windows are not shielded (i.e., they have full line-of-sight to the arriving aircraft)
From page 107...
... Findings and Applications 107 4.9 Comparison of Measurement Results from Loudspeaker and Flyover Testing It is reasonable to assume that if both the loudspeaker and the flyover measurement methods are valid and properly conducted, the NLR results from the two should closely agree. Unfortunately, this is not always the case, as shown by measurements for this study and previously those for the ATAC study, "Study of Noise Level Reduction (NLR)
From page 108...
... 108 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs incidence, materials are typically acoustically isotropic in that they produce the same TL when tested from either side of the building element. The actual frequencies for the first panel resonance, other resonances, and coincidence areas may be computed from the mass and stiffness properties of the various materials.
From page 109...
... Findings and Applications 109 • Façades are composed of different elements, some more susceptible to angle of incidence than are others. • The TL is not isotropic but orthotropic, meaning that the TL varies with direction.
From page 110...
... 110 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs Center, 1999)
From page 111...
... Findings and Applications 111 4.10.1 External Sound Spectra A significant factor that affects the measured noise reduction is the external sound spectra (i.e., the noise "signature" of aircraft overflights at a given airport)
From page 112...
... 112 Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs [NOTE: The above task 2.a is the same for both sound intensity and the interior loudspeaker described just above. These two methods depart in terms of the outdoor measurements.

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