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Code of Federal Regulations (Last Updated: November 8, 2024) |
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Title 14 - Aeronautics and Space |
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Chapter I - Federal Aviation Administration, Department of Transportation |
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SubChapter C - Aircraft |
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Part 21 - Certification Procedures for Products and Articles |
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Subpart B - Type Certificates |
Appendix B to Part 36 - Aircraft Noise Evaluation Under § 36.103
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Sec. B36.1 General. B36.3 Perceived noise level. B36.5 Correction for spectral irregularities. B36.7 Maximum tone corrected perceived noise level. B36.9 Duration correction. B36.11 Effective perceived noise level. B36.13 Mathematical formulation of noy tables. Section B36.1
General. The procedures in this appendix must be used to determine the noise evaluation quantity designated as effective perceived noise level, EPNL, under §§ 36.103 and 36.803. These procedures, which use the physical properties of noise measured as prescribed by appendix A of this part, consist of the following:(a) The 24 one-third octave bands of sound pressure level are converted to perceived noisiness by means of a noy table. The noy values are combined and then converted to instantaneous perceived noise levels, PNL(k).
(b) A tone correction factor, C(k), is calculated for each spectrum to account for the subjective response to the presence of the maximum tone.
(c) The tone correction factor is added to the perceived noise level to obtain tone corrected perceived noise levels, PNLT(k), at each one-half second increment of time. The instantaneous values of tone corrected perceived noise level are noted with respect to time and the maximum value, PNLTM, is determined.
PNLT(k)=PNL(k)+C(k) (d) A duration correction factor, D, is computed by integration under the curve of tone corrected perceived noise level versus time.
(e) Effective perceived noise level, EPNL, is determined by the algebraic sum of the maximum tone corrected perceived noise level and the duration correction factor.
EPNL=PNLTM+D Section B36.3
Perceived noise level. Instantaneous perceived noise levels, PNL(k), must be calculated from instantaneous one-third octave band sound pressure levels, SPL(i,k), as follows:(a)
Step 1. Convert each one-third octave band SPL(i,k), from 50 to 10,000 Hz, to perceived noisiness, n(i,k), by reference to Table B1, or to the mathematical formulation of the noy table given in § B36.13 of this appendix.(b)
Step 2. Combine the perceived noisiness values, n(i,k), found in step 1 by the following formula:N(k)=
n (k)+0.15 [[Σ 2 4i−1 n(i,k)]−
n (k)]=0.85n(K)+0.15 Σ 24i−1n(i,k) where n (k) is the largest of the 24 values of n(i,k) and N(k) is the total perceived noisiness.(c)
Step 3. Convert the total perceived noisiness, N(k), into perceived noise level, PNL(k), by the following formula:PNL(k)=40.0+33.22 log N(k) which is plotted in Figure B1. PNL(k) may also be obtained by choosing N(k) in the 1,000 Hz column of Table B1 and then reading the corresponding value of SPL(i,k) which, at 1,000 Hz, equals PNL(k). EC28SE91.103 Table B1 Perceived Noisiness (NOYs) as a Function of Sound Pressure Level SPL 1/3 Octave Band Center Frequencies in Hz (c/s)50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000 4 0.10 0.10 5 0.10 0.11 0.10 6 0.11 0.12 0.11 7 0.13 0.14 0.13 0.10 8 0.14 0.16 0.14 0.11 9 0.10 0.16 0.17 0.16 0.14 10 0.11 0.17 0.19 0.18 0.16 0.10 11 0.13 0.19 0.22 0.21 0.18 0.12 12 0.10 0.14 0.22 0.24 0.24 0.21 0.14 12 0.11 0.16 0.24 0.27 0.27 0.24 0.16 14 0.13 0.18 0.27 0.30 0.30 0.27 0.19 15 0.10 0.14 0.21 0.30 0.33 0.33 0.30 0.22 16 0.10 0.10 0.10 0.10 0.10 0.11 0.16 0.24 0.33 0.35 0.35 0.33 0.26 17 0.11 0.11 0.11 0.11 0.11 0.13 0.18 0.27 0.35 0.38 0.38 0.35 0.30 0.10 18 0.10 0.13 0.13 0.13 0.13 0.13 0.15 0.21 0.30 0.38 0.41 0.41 0.38 0.33 0.12 19 0.11 0.14 0.14 0.14 0.14 0.14 0.17 0.24 0.33 0.41 0.45 0.45 0.41 0.36 0.14 20 0.13 0.16 0.16 0.16 0.16 0.16 0.20 0.27 0.36 0.45 0.49 0.49 0.45 0.39 0.17 21 0.10 0.14 0.18 0.18 0.18 0.18 0.18 0.23 0.30 0.39 0.49 0.53 0.53 0.46 0.42 0.21 0.10 22 0.11 0.16 0.21 0.21 0.21 0.21 0.21 0.26 0.33 0.42 0.53 0.57 0.57 0.53 0.46 0.25 0.11 23 0.13 0.18 0.24 0.24 0.24 0.24 0.24 0.30 0.36 0.46 0.57 0.62 0.62 0.57 0.50 0.30 0.13 24 0.10 0.14 0.21 0.27 0.27 0.27 0.27 0.27 0.33 0.40 0.50 0.62 0.67 0.67 0.62 0.55 0.33 0.15 25 0.11 0.16 0.24 0.30 0.30 0.30 0.30 0.30 0.35 0.43 0.55 0.67 0.73 0.73 0.67 0.60 0.36 0.17 26 0.13 0.18 0.27 0.33 0.33 0.33 0.33 0.33 0.38 0.48 0.60 0.73 0.79 0.79 0.73 0.65 0.39 0.20 27 0.10 0.14 0.21 0.30 0.35 0.35 0.35 0.35 0.35 0.41 0.52 0.65 0.79 0.85 0.85 0.79 0.71 0.42 0.23 28 0.11 0.16 0.24 0.33 0.38 0.38 0.38 0.38 0.38 0.45 0.57 0.71 0.85 0.92 0.92 0.85 0.77 0.46 0.26 29 0.13 0.18 0.27 0.35 0.41 0.41 0.41 0.41 0.41 0.49 0.63 0.77 0.92 1.00 1.00 0.92 0.84 0.50 0.30 30 0.10 0.14 0.21 0.30 0.38 0.45 0.45 0.45 0.45 0.45 0.53 0.69 0.84 1.00 1.07 1.07 1.00 0.92 0.55 0.33 31 0.11 0.16 0.24 0.33 0.41 0.49 0.49 0.49 0.49 0.49 0.57 0.76 0.92 1.07 1.15 1.15 1.07 1.00 0.60 0.37 32 0.13 0.18 0.27 0.36 0.45 0.53 0.53 0.53 0.53 0.53 0.62 0.83 1.00 1.15 1.23 1.23 1.15 1.07 0.65 0.41 33 0.14 0.21 0.30 0.39 0.49 0.57 0.57 0.57 0.57 0.57 0.67 0.91 1.07 1.23 1.32 1.32 1.23 1.15 0.71 0.45 34 0.10 0.16 0.24 0.33 0.42 0.53 0.62 0.62 0.62 0.62 0.62 0.73 1.00 1.15 1.32 1.41 1.41 1.32 1.23 0.77 0.50 35 0.11 0.18 0.27 0.36 0.46 0.57 0.67 0.67 0.67 0.67 0.67 0.79 1.07 1.23 1.41 1.51 1.51 1.41 1.32 0.84 0.55 36 0.13 0.21 0.30 0.40 0.50 0.62 0.73 0.73 0.73 0.73 0.73 0.85 1.15 1.32 1.51 1.62 1.62 1.51 1.41 0.92 0.61 37 0.15 0.24 0.33 0.43 0.55 0.67 0.79 0.79 0.79 0.79 0.79 0.92 1.23 1.41 1.62 1.74 1.74 1.62 1.51 1.00 0.67 38 0.17 0.27 0.37 0.48 0.60 0.73 0.85 0.85 0.85 0.85 0.85 1.00 1.32 1.51 1.74 1.86 1.86 1.74 1.62 1.10 0.74 39 0.10 0.20 0.30 0.41 0.52 0.65 0.79 0.92 0.92 0.92 0.92 0.92 1.07 1.41 1.62 1.86 1.99 1.99 1.86 1.74 1.21 0.82 40 0.12 0.23 0.33 0.45 0.57 0.71 0.85 1.00 1.00 1.00 1.00 1.00 1.15 1.51 1.74 1.99 2.14 2.14 1.99 1.86 1.34 0.90 41 0.14 0.26 0.37 0.50 0.63 0.77 0.92 1.07 1.07 1.07 1.07 1.07 1.23 1.62 1.86 2.14 2.29 2.29 2.14 1.99 1.48 1.00 42 0.16 0.30 0.41 0.55 0.69 0.84 1.00 1.15 1.15 1.15 1.15 1.15 1.32 1.74 1.99 2.29 2.45 2.45 2.29 2.14 1.63 1.10 43 0.19 0.33 0.45 0.61 0.76 0.92 1.07 1.23 1.23 1.23 1.23 1.23 1.41 1.86 2.14 2.45 2.63 2.63 2.45 2.29 1.79 1.21 44 0.10 0.22 0.37 0.50 0.67 0.83 1.00 1.15 1.32 1.32 1.32 1.32 1.32 1.52 1.99 2.29 2.63 2.81 2.81 2.63 2.45 1.99 1.34 45 0.12 0.26 0.42 0.55 0.74 0.91 1.08 1.24 1.41 1.41 1.41 1.41 1.41 1.62 2.14 2.45 2.81 3.02 3.02 2.81 2.63 2.14 1.48 46 0.14 0.30 0.46 0.61 0.82 1.00 1.16 1.33 1.52 1.52 1.52 1.52 1.52 1.74 2.29 2.63 3.02 3.23 3.23 3.02 2.81 2.29 1.63 47 0.16 0.34 0.52 0.67 0.90 1.08 1.25 1.42 1.62 1.62 1.62 1.62 1.62 1.87 2.45 2.81 3.23 3.46 3.46 3.23 3.02 2.45 1.79 48 0.19 0.38 0.58 0.74 1.00 1.17 1.34 1.53 1.74 1.74 1.74 1.74 1.74 2.00 2.63 3.02 3.46 3.71 3.71 3.46 3.23 2.63 1.98 49 0.10 0.22 0.43 0.65 0.82 1.08 1.26 1.45 1.64 1.87 1.87 1.87 1.87 1.87 2.14 2.81 3.23 3.71 3.97 3.97 3.71 3.46 2.81 2.18 50 0.12 0.26 0.49 0.72 0.90 1.17 1.36 1.56 1.76 2.00 2.00 2.00 2.00 2.00 2.30 3.02 3.46 3.97 4.26 4.26 3.97 3.71 3.02 2.40 51 0.14 0.30 0.55 0.80 1.00 1.26 1.47 1.68 1.89 2.14 2.14 2.14 2.14 2.14 2.46 3.23 3.71 4.26 4.56 4.56 4.26 3.97 3.23 2.63 52 0.17 0.34 0.62 0.90 1.08 1.36 1.58 1.80 2.03 2.30 2.30 2.30 2.30 2.30 2.64 3.46 3.97 4.56 4.89 4.89 4.56 4.26 3.46 2.81 53 0.21 0.39 0.70 1.00 1.18 1.47 1.71 1.94 2.17 2.46 2.46 2.46 2.46 2.46 2.83 3.71 4.26 4.69 5.24 5.24 4.89 4.56 3.71 3.02 54 0.25 0.45 0.79 1.09 1.28 1.50 1.85 2.09 2.33 2.64 2.64 2.64 2.64 2.64 3.03 3.97 4.56 5.24 5.61 5.61 5.24 4.89 3.97 3.23 55 0.30 0.51 0.89 1.18 1.39 1.71 2.00 2.25 2.50 2.83 2.83 2.83 2.83 2.83 3.25 4.26 4.89 5.61 6.01 6.01 5.61 5.24 4.26 3.46 56 0.34 0.59 1.00 1.29 1.50 1.85 2.15 2.42 2.69 3.03 3.03 3.03 3.03 3.03 3.48 4.56 5.24 6.01 6.44 6.44 6.01 5.61 4.56 3.71 57 0.39 0.67 1.09 1.40 1.63 2.00 2.33 2.61 2.88 3.25 3.25 3.25 3.25 3.25 3.73 4.89 5.61 6.44 6.90 6.90 6.44 6.01 4.89 3.97 58 0.45 0.77 1.18 1.53 1.77 2.15 2.51 2.81 3.10 3.48 3.48 3.48 3.48 3.48 4.00 5.24 6.01 6.90 7.39 7.39 6.90 6.44 5.24 4.26 59 0.51 0.87 1.29 1.66 1.92 2.33 2.71 3.03 3.32 3.73 3.73 3.73 3.73 3.73 4.29 5.61 6.44 7.39 7.92 7.92 7.39 6.90 5.61 4.56 60 0.59 1.00 1.40 1.81 2.08 2.51 2.93 3.26 3.57 4.00 4.00 4.00 4.00 4.00 4.59 6.01 6.90 7.92 8.49 8.49 7.92 7.39 6.01 4.89 61 0.67 1.10 1.53 1.97 2.26 2.71 3.16 3.51 3.83 4.29 4.29 4.29 4.29 4.29 4.92 6.44 7.39 8.49 9.09 9.09 8.49 7.92 6.44 5.24 62 0.77 1.21 1.66 2.15 2.45 2.93 3.41 3.79 4.11 4.59 4.59 4.59 4.59 4.59 5.28 6.90 7.92 9.09 9.74 9.74 9.09 8.49 6.90 5.61 63 0.87 1.32 1.81 2.34 2.65 3.16 3.69 4.06 4.41 4.92 4.92 4.92 4.92 4.92 5.66 7.39 8.49 9.74 10.4 10.4 9.74 9.09 7.39 6.01 64 1.00 1.45 1.97 2.54 2.88 3.41 3.98 4.39 4.73 5.28 5.28 5.28 5.28 5.28 6.06 7.52 9.09 10.4 11.2 11.2 10.4 9.74 7.92 6.44 65 1.11 1.60 2.15 2.77 3.12 3.69 4.30 4.71 5.08 5.66 5.66 5.66 5.66 5.66 6.50 8.49 9.74 11.2 12.0 12.0 11.2 10.4 8.49 6.90 66 1.22 1.75 2.34 3.01 3.39 3.99 4.64 5.07 5.45 6.06 6.06 6.06 6.06 6.06 6.96 9.09 10.4 12.0 12.8 12.8 12.0 11.2 9.09 7.39 67 1.35 1.92 2.54 3.28 3.68 4.30 5.01 5.46 5.85 6.50 6.50 6.50 6.50 6.50 7.46 9.74 11.2 12.8 13.8 13.8 12.8 12.0 9.74 7.92 68 1.49 2.11 2.77 3.57 3.99 4.64 5.41 5.88 6.27 6.96 6.96 6.96 6.96 6.96 8.00 10.4 12.0 13.8 14.7 14.7 13.8 12.8 10.4 8.49 69 1.65 2.32 3.01 3.80 4.33 5.01 5.84 6.33 6.73 7.46 7.46 7.46 7.46 7.46 8.57 11.2 12.8 14.7 15.8 15.8 14.7 13.8 11.2 9.09 70 1.82 2.59 3.28 4.23 4.69 5.41 6.31 6.81 7.23 8.00 8.00 8.00 8.00 8.00 9.19 12.0 13.8 15.8 16.9 16.9 15.8 14.7 12.0 9.74 71 2.02 2.79 3.57 4.60 5.09 5.84 6.81 7.33 7.75 8.57 8.57 8.57 8.57 8.57 9.85 12.8 14.7 16.9 18.1 18.1 16.9 15.8 12.8 10.4 72 2.23 3.07 3.88 5.01 5.52 6.31 7.36 7.90 8.32 9.19 9.19 9.19 9.19 9.19 10.6 13.8 15.8 18.1 19.4 19.4 18.1 16.9 13.8 11.2 73 2.46 3.37 4.23 5.45 5.99 6.81 7.94 8.50 8.93 9.85 9.85 9.85 9.85 9.85 11.3 14.7 16.9 19.4 20.8 20.8 19.4 18.1 14.7 12.0 74 2.72 3.70 4.60 5.94 6.50 7.36 8.57 9.15 9.59 10.6 10.6 10.6 10.6 10.6 12.1 15.8 18.1 20.8 22.3 22.3 20.8 19.4 15.8 12.8 75 3.01 4.06 5.01 6.46 7.05 7.94 9.19 9.85 10.3 11.3 11.3 11.3 11.3 11.3 13.0 16.9 19.4 22.3 23.9 23.9 22.3 20.8 16.9 13.8 76 3.32 4.46 5.45 7.03 7.65 8.57 9.85 10.6 11.0 12.1 12.1 12.1 12.1 12.1 13.9 18.1 20.8 23.9 25.6 25.6 23.9 22.3 18.1 14.7 77 3.67 4.89 5.94 7.66 8.29 9.19 10.6 11.3 11.8 13.0 13.0 13.0 13.0 13.0 14.9 19.4 22.3 25.6 27.4 27.4 25.6 23.9 19.4 15.8 78 4.06 5.37 6.46 8.33 9.00 9.85 11.3 12.1 12.7 13.9 13.9 13.9 13.9 13.9 16.0 20.8 23.9 27.4 29.4 29.4 27.4 25.6 20.8 16.9 79 4.49 5.90 7.03 9.07 9.76 10.6 12.1 13.0 13.6 14.9 14.9 14.9 14.9 14.9 17.1 22.3 25.6 29L4 31.5 31.5 29.4 27.4 22.3 18.1 80 4.96 6.48 7.66 9.85 10.6 11.3 13.0 13.9 14.6 16.0 16.0 16.0 16.0 16.0 18.4 23.9 27.4 31.5 33.7 33.7 31.5 29.4 23.9 19.4 81 5.48 7.11 8.33 10.6 11.3 12.1 13.9 14.9 15.7 17.1 17.1 17.1 17.1 17.1 19.7 25.6 29.4 33.7 36.1 36.1 33.7 31.5 25.6 20.8 82 6.06 7.81 9.07 11.3 12.1 13.0 14.9 16.0 16.9 18.4 18.4 18.4 18.4 18.4 21.1 27.4 31.5 36.1 38.7 38.7 36.1 33.7 27.4 22.3 83 6.70 8.57 9.87 12.1 13.0 13.9 16.0 17.1 18.1 19.7 19.7 19.7 19.7 19.7 22.6 29.4 33.7 38.7 41.5 41.5 38.7 36.1 29.4 23.9 84 7.41 9.41 10.7 13.0 13.9 14.9 17.1 18.4 19.4 21.1 21.1 21.1 21.1 21.1 24.3 31.5 36.1 41.5 44.4 44.4 41.5 38.7 31.5 25.6 85 8.19 10.3 11.7 13.9 14.9 16.0 18.4 19.7 20.8 22.6 22.6 22.6 22.6 22.6 26.0 33.7 38.7 44.4 47.6 47.6 44.4 41.5 33.7 27.4 86 9.05 11.3 12.7 14.9 16.0 17.1 19.7 21.1 22.4 24.3 24.3 24.3 24.3 24.3 27.9 36.1 41.5 47.6 51.0 51.0 47.6 44.4 36.1 29.4 87 10.0 12.1 13.9 16.0 17.1 18.4 21.1 22.6 24.0 26.0 26.0 26.0 26.0 26.0 29.9 38.7 44.4 51.0 54.7 54.7 51.0 47.6 38.7 31.5 88 11.1 13.0 14.9 17.1 18.4 19.7 22.6 24.3 25.8 27.9 27.9 27.9 27.9 27.9 32.0 41.5 47.6 54.7 58.6 58.6 54.7 51.0 41.5 33.7 89 12.2 13.9 16 .0 18.4 19.7 21.1 24.3 26.0 27.7 29.9 29.9 29.9 29.9 29.9 34.3 44.4 51.0 58.6 62.7 62.7 58.6 54.7 44.4 36.1 90 13.5 14.9 17.1 19.7 21.1 22.6 26.0 27.9 29.7 32.0 32.0 32.0 32.0 32.0 36.8 47.6 54.7 62.7 67.2 67.2 62.7 58.6 47.6 38.7 91 14.9 16.0 18.4 21.1 22.6 24.3 27.9 29.9 31.8 34.3 34.3 34.3 34.3 34.3 39.4 51.0 58.6 67.2 72.6 72.0 67.2 62.7 51.0 41.5 92 16.0 17.1 19.7 22.6 24.3 26.0 29.9 32.0 34.2 36.8 36.8 36.8 36.8 36.8 42.2 54.7 62.7 72.0 77.2 77.2 72.0 67.2 54.7 44.4 93 17.1 18.4 21.1 24.3 26.0 27.9 32.0 34.3 36.7 39.4 39.4 39.4 39.4 39.4 45.3 58.6 67.2 77.2 82.7 82.7 77.2 72.0 58.6 47.6 94 18.4 19.7 22.6 26.0 27.9 29.9 34.3 36.8 39.4 42.2 42.2 42.2 42.2 42.2 48.5 62.7 72.0 82.7 88.6 88.6 82.7 77.2 62.7 51.0 95 19.7 21.1 24.3 27.9 29.9 32.0 36.8 39.4 42.2 45.3 45.3 45.3 45.3 45.3 52.0 67.2 77.2 88.6 94.9 94.9 88.6 82.7 67.2 54.7 96 21.1 22.6 26.0 29.9 32.0 34.3 39.4 42.2 45.3 48.5 48.5 48.5 48.5 48.5 55.7 72.0 82.7 94.9 102 102 94.9 88.6 72.0 58.6 97 22.6 24.3 27.9 32.0 34.3 36.8 42.2 45.3 48.5 52.0 52.0 52.0 52.0 52.0 59.7 77.2 88.6 102 109 109 102 94.9 77.2 62.7 98 24.3 26.0 29.9 34.3 36.8 39.4 45.3 48.5 52.0 55.7 55.7 55.7 55.7 55.7 64.0 82.7 94.9 109 117 117 105 102 82.7 67.2 99 26.0 27.9 32.0 36.8 39.4 42.2 48.5 52.0 55.7 59.7 59.7 59.7 59.7 59.7 68.6 88.6 102 117 125 125 117 109 88.6 72.0 100 27.9 29.9 34.3 39.4 42.2 45.3 52.0 55.7 59.7 64.0 64.0 64.0 64.0 64.0 73.5 94.9 109 125 134 134 125 117 94.9 77.2 101 29.9 32.0 36.8 42.2 45.3 48.5 55.7 59.7 64.0 68.6 68.6 68.6 68.6 68.6 78.8 102 117 134 144 144 134 125 102 82.7 102 32.0 34.3 39.4 45.3 48.5 52.0 59.7 64.0 68.6 73.5 73.5 73.5 73.5 73.5 84.4 109 125 144 154 154 144 134 109 88.6 103 34.3 36.8 42.2 48.5 52.0 55.7 64.0 68.6 73.5 78.8 78.8 78.8 78.8 78.8 90.5 117 134 154 165 165 154 144 117 94.9 104 36.8 39.4 45.3 52.0 55.7 59.7 68.6 73.5 78.8 84.4 84.4 84.4 84.4 84.4 97.0 125 144 165 177 177 165 154 125 102 105 39.4 42.2 48.5 55.7 59.7 64.0 73.5 78.8 84.4 90.5 90.5 90.5 90.5 90.5 104 134 154 177 189 189 177 165 134 109 106 42.2 45.3 52.0 59.7 64.0 68.6 78.8 84.4 90.5 97.0 97.0 97.0 97.0 97.0 111 144 165 189 203 203 189 177 144 117 107 45.3 48.5 55.7 64.0 68.6 73.5 84.4 90.5 97.0 104 104 104 104 104 119 154 177 203 217 217 203 109 154 125 108 48.5 52.0 59.7 68.6 73.5 78.8 90.5 97.0 104 111 111 111 111 111 128 165 189 217 233 233 217 203 165 134 109 52.0 55.7 64.0 73.5 78.8 84.4 97.0 104 111 119 119 119 119 119 137 177 203 233 249 249 233 217 177 144 110 55.7 59.7 68.6 78.8 84.4 90.5 104 111 119 128 128 128 128 128 137 189 217 249 267 267 249 233 189 154 111 59.7 64.0 73.5 84.4 90.5 97.0 111 119 128 137 137 137 137 137 158 203 233 267 286 286 267 249 203 165 112 64.0 68.6 78.8 90.4 97.0 104 119 128 137 147 147 147 147 147 169 217 249 286 307 307 286 267 217 177 113 64.6 73.5 84.4 97.0 104 111 128 137 147 158 158 158 158 158 181 233 267 307 329 329 307 286 233 189 114 73.5 78.8 50.5 104 111 119 137 147 158 169 169 169 169 169 194 249 286 329 352 352 329 307 249 203 115 78.8 84.4 97.0 111 119 128 147 158 169 181 181 181 181 181 208 267 307 352 377 377 352 329 267 217 116 84.4 90.5 104 119 128 137 158 169 181 194 194 194 194 194 223 286 329 377 404 404 377 352 286 233 117 90.5 97.6 111 128 137 147 169 181 194 208 208 208 208 208 239 307 352 404 433 433 404 377 307 249 118 97.0 104 119 137 147 158 181 194 208 223 223 223 223 223 256 329 377 433 464 464 433 404 329 267 119 104 111 128 147 158 169 194 208 223 239 239 239 239 239 274 352 404 464 497 497 464 433 352 286 120 111 119 137 158 169 181 208 223 239 256 256 256 256 256 294 377 433 497 533 533 497 464 377 307 121 119 128 147 169 181 194 223 239 256 274 274 274 274 274 315 404 464 533 571 571 533 497 404 329 122 128 137 158 181 194 208 239 256 274 294 294 294 294 294 338 433 497 571 611 611 571 533 433 352 123 137 147 169 194 208 223 256 274 294 315 315 315 315 315 362 464 533 611 655 655 611 571 464 377 124 147 158 181 208 223 239 274 294 315 338 338 338 338 338 388 497 571 655 702 702 655 611 497 404 125 158 169 194 223 239 256 294 315 338 362 362 362 362 362 416 533 611 702 752 752 702 655 533 433 126 169 181 208 239 256 274 315 338 362 388 388 388 388 388 446 571 655 752 806 806 752 702 571 464 127 181 194 223 256 274 294 338 362 388 416 416 416 416 416 479 611 702 806 863 863 606 732 611 497 128 194 208 239 274 294 315 362 388 416 446 446 446 446 446 512 655 752 863 925 925 863 806 655 533 129 208 223 256 294 315 338 388 416 446 478 478 478 478 478 549 702 806 925 991 991 925 863 702 571 130 223 239 274 315 338 362 416 446 478 512 512 512 512 512 588 752 863 991 1062 1062 991 925 752 611 131 239 256 294 338 362 388 446 478 512 549 549 549 549 549 630 806 925 1062 1137 1137 1062 991 606 655 132 256 274 315 362 388 416 478 512 549 588 588 588 588 588 676 863 991 1137 1219 1219 1137 1062 863 702 133 274 294 338 388 416 446 512 549 588 630 630 630 630 630 724 925 1062 1219 1306 1306 1219 1137 925 752 134 294 315 362 416 446 478 549 588 630 676 676 676 676 676 776 991 1137 1306 1399 1399 1306 1219 991 606 135 315 338 388 446 478 512 588 630 676 724 724 724 724 724 832 1062 1219 1399 1499 1499 1399 1306 1062 863 136 338 362 416 478 512 549 630 676 724 776 776 776 776 776 891 1137 1306 1499 1606 1606 1499 1399 1197 925 137 362 388 446 512 549 588 676 724 776 832 832 832 832 832 955 1219 1399 1606 1721 1721 1606 1499 1219 991 138 398 416 478 549 588 630 724 776 832 891 891 891 891 891 1024 1306 1499 1721 1844 1844 1721 1606 1306 1062 139 416 446 512 588 630 676 776 832 891 955 955 955 955 955 1098 1399 1606 1844 1975 1975 1844 1721 1399 1137 140 446 478 549 630 676 724 832 891 955 1024 1024 1024 1024 1024 1176 1499 1721 1975 1975 1844 1499 1219 141 478 512 588 676 724 776 891 955 1024 1098 1098 1098 1098 1098 1261 1606 1844 1975 1606 1306 142 512 549 630 724 776 832 955 1024 1098 1176 1176 1176 1176 1176 1351 1721 1975 1721 1399 143 549 588 676 776 832 891 1024 1098 1176 1261 1261 1261 1261 1261 1448 1844 1844 1499 144 588 630 724 832 891 955 1098 1176 1261 1351 1351 1351 1351 1351 1552 1975 1975 1606 145 630 676 776 891 955 1024 1176 1261 1351 1448 1448 1448 1448 1448 1664 1721 146 676 724 832 955 1024 1098 1261 1351 1448 1552 1552 1552 1552 1552 1783 1844 147 724 776 891 1024 1098 1176 1351 1448 1552 1664 1664 1664 1664 1664 1911 1975 148 776 832 955 1098 1176 1261 1448 1552 1664 1783 1783 1783 1783 1783 2048 149 832 891 1024 1176 1261 1351 1552 1664 1783 1911 1911 1911 1911 1911 150 891 955 1098 1261 1351 1448 1664 1783 1911 2048 2048 2048 2048 2048 Section B36.5
Correction for spectral irregularities. Noise having pronounced irregularities in the spectrum (for example, discrete frequency components or tones), must be adjusted by the correction factor C(k) calculated as follows:(a)
Step 1. Starting with the corrected sound pressure level in the 80 Hz one-third octave band (band number 3), calculate the changes in sound pressure level (or “slopes”) in the remainder of the one-third octave bands as follows:s(3,k)=no value
s(4,k)=SPL(4,k)−SPL(3,k)
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.
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s(i,k)=SPL(i,k)−SPL[(i−l),k]
.
.
.
s(24,k)=SPL(24,k)−SPL(23,k)
(b)
Step 2. Encircle the value of the slope, s(i,k), where the absolute value of the change in slope is greater than 5; that is, where∥ Δ s(i,k)∥ =∥ s(i,k)−s[(i−1),k]∥ >5(c)
Step 3. (1) If the encircled value of the slope s(i,k) is positive and algebraically greater than the slope s[(i−1),k], encircle SPL(I,K).(2) If the encircled value of the slope s(1,k) is zero or negative and the slope s[i−1),k] is positive, encircle (SPL[(i−1),k])
(3) For all other cases, no sound pressure level value is to be encircled.
(d)
Step 4. Omit all SPL(i,k) encircled in Step 3 and compute new sound pressure levels SPL'prime;(i,k) as follows:(1) For nonencircled sound pressure levels, let the new sound pressure levels equal the original sound pressure levels,
SPL′(i,k)=SPL(i,k) (2) For encircled sound pressure levels in bands 1-23, let the new sound pressure level equal the arithmetic average of the preceding and following sound pressure levels.
SPL′(i,k)=( 1/2 )[SPL[(i−1),k]+SPL[(i+1),k]](3) If the sound pressure level in the highest frequency band (i=24) is encircled, let the new sound pressure level in that band equal
SPL′(24,k)=SPL(23,k+s(23,k). (e)
Step 5. Recompute new slopes s′ (i,k), including one for an imaginary 25-th band, as follows:s′(3,k)=s′(4,k)
s′(4,k)=SPL′(4,k)−SPL′(3,k)
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s′(i,k)=SPL′(i,k)−SPL′[(i−1),k]
s′(24,k)=SPL′(24,k)−SPL′(23,k)
s′(25,k)=s′(24,k)
(f)
Step 6. For i from 3 to 23, compute the arithmetic average of the three adjacent slopes as follows:s(i,k)=( 1/3 )[s′(i,k)+s′[(i+1),k] +s′[(i+2),k]](g)
Step 7. Compute final adjusted one-third octave-band sound pressure levels, SPL″ (i,k), by beginning with band number 3 and proceeding to band number 24 as follows:SPL″(3,k)=SPL(3,k)
SPL″(4,k)=SPL″(3.k)+s(3.k)
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SPL″(i,k)=SPL″[(i−1),k]+s[(i−1),k]
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SPL″(24,k)=SPL″(23,k)+s(23,k)
(h)
Step 8. Calculate the differences, F(i,k), between the original and the adjusted sound pressure levels as follows:F(i,k)=SPL(i,k)−SPL″(i,k) and note only value greater than one and a half. (i)
Step 9. For each of the 24 one-third octave bands, determine tone correction factors from the sound pressure level differences F(i,k) and Table B2.EC28SE91.104 Frequency f, Hz Level difference F, dB Tone correction C, dB 50 ≤ f< 5001 1/2 *≤ F< 3F/3− 1/2 3 ≤ F< 20F/6 20 ≤ F3 1/2 500 ≤ f≤ 5,0001 1/2 *≤ F< 32 F/3−1 3 ≤ F< 20F/3 20 ≤ F6 2/3 5,000 < f≤ 10,0001 1/2 *≤ F< 3F/3− 1/2 3 ≤ F< 20F/6 20 ≤ F3 1/3 * See Step 8. (j)
Step 10. Designate the largest of the tone correction factors, determined in Step 9, as C(k). An example of the tone correction procedure is given in Table B3.(k) Tone corrected perceived noise levels PNLT(k) are determined by adding the C(k) values to corresponding PNL(k) values, that is,
PNLT(k)=PNL(k)+C(k) (l) For any i-th one-third octave band, at any k-th increment of time, for which the tone correction factor is suspected to result from something other than (or in addition to) an actual tone (or any special irregularity other than aircraft noise), an additional analysis may be made using a filter with a bandwidth narrower than one-third of an octave. If the narrow band analysis corroborates that suspicion, then a revised value for the background sound pressure level, SPL″(i,k) may be determined from the analysis and used to compute a revised tone correction factor, F(i,k), for that particular one-third octave band.
(m) Tones resulting from ground-plane reflections in the 800 Hz and lower one-third octave bands may be excluded from the calculation of corrections for spectral irregularities. To qualify for this exclusion, the pseudotones must be clearly identified as not being related to the engine noise. This identification may be made either by comparing measured data with data from a flush
mounted microphone, or by observing the Doppler shift characteristics of the tone during the flyover-noise/time history. Since pseudotones are related to ground reflections, a microphone mounted flush to the ground will yield a spectral shape which can be distinguished from that produced by the 4-foot high microphone at those frequencies which can be related to ground reflection's geometrical relationships. Identification through Doppler shifting (the symmetric variation of frequency with time) can be made because the Doppler frequency variation yields a frequency increase for an approaching signal and a frequency decrease for a receding signal. Pseudotones at frequencies above 800 Hz generally should not yield significant tone corrections. However, for consistency, each tone correction value must be included in the computation for spectral irregularities. While the tone corrections below 800 Hz may be ignored for the spectral irregularity correction, the SPL values must be included in the noy calculation prescribed in section B36.13 of this appendix. (n) After the value of PNLTM for each flyover-noise/time history, is identified, the frequency for the largest tone correction factor (C(k)) must be identified for the two preceding and the two succeeding, 500-milli-second time intervals, to identify possible tone suppression at PNLTM as a result of band sharing of the tone. If the value of C(k) for PNLTM is less than the average value of C(k) for those five consecutive time intervals, that average value of C(k) must be used to compute a new value for PNLTM.
Section B36.7
Maximum tone corrected perceived noise level. (a) The maximum tone corrected perceived noise level, PNLTM, is the maximum calculated value of the tone corrected perceived noise level, PNLT(k), calculated in accordance with the procedure of section B36.5 of this appendix. Figure B2 is an example of a flyover noise time history where the maximum value is clearly indicated. Half-second time intervals,Δ t, are small enough to obtain a satisfactory noise time history.EC28SE91.105 (b) If there are no pronounced irregularities in the spectrum, then the procedure of § B36.5 of this appendix would be redundant since PNLT(k) would be identically equal to PNL(k). For this case, PNLTM would be the maximum value of PNL(k) and would equal PNLM.
Section B36.9
Duration correction. The duration correction factor D is determined by the integration technique defined by the expression:EC28SE91.107 Where T is a normalizing time constant, PNLTM is the maximum value of PNLT, and t(1) and t(2) are the limits of the significant noise time history. (a) Since PNLT is calculated from measured values of SPL, there will, in general, be no obvious equation for PNLT as a function of time. Consequently, the equation can be rewritten with a summation sign instead of an integral sign as follows:
where Δ t is the length of the equal increments of time for which PNLT(k) is calculated and d is the time interval to the nearest 1.0 second during which PNLT(k) is within a specified value, h, of PNLTM.(b) Half-second time intervals for
Δ t are small enough to obtain a satisfactory history of the perceived noise level. A shorter time interval may be selected by the applicant provided approved limits and constants are used.(c) The following values for T,
Δ t,and h, must be used in calculating D:T=10 sec, Δ t=0.5 sec. (or the approved sampling time interval), andh=10 dB. Using the above values, the equation for D becomes Where the integer d is the duration time defined by the points that are 10 dB less than PNLTM. (d) If the 10 dB-down points fall between calculated PNLT(k) values (the usual case), the applicable limits for the duration time must be chosen from the PNLT(k) values closest to PNLTM−10. For those cases with more than one peak value of PNLT(k), the applicable limits must be chosen to yield the largest possible value for the duration time.
(e) If the value of PNLT(k) at the 10 dB-down points is 90 PNdB or less, the value of d may be taken as the time interval between the initial and the final times for which PNLT(k) equals 90 PNdB.
(f) The aircraft testing procedures must include the 10 dB-down points in the flyover noise/time record.
Section B36.11
Effective perceived noise level. (a) The total subjective effect of an aircraft flyover is designated “effective perceived noise level,” EPNL, and is equal to the algebraic sum of the maximum value of the tone corrected perceived noise level, PNLTM, and the duration correction, D. That is,EPNL=PNLTM+D where PNLTM and D are calculated under sections B36.7 and B36.9 of this appendix. (b) The above equation can be rewritten by substituting the equation for D from § B36.9 of this appendix, that is,
(c) If, during a test flight, one or more peak values of PNLT are observed which are within 2 dB of PNLTM, the value of EPNL shall be calculated for each, as well as for PNLTM. If any EPNL value exceeds the value at the moment of PNLTM, the maximum value of such exceedance must be added as a further adjustment to the EPNL calculated from the measured data.
Section B36.13
Mathematical formulation of noy tables. (a) The relationship between sound pressure level and perceived noisiness given in Table B1 is illustrated in Figure B3. The variation of log (n) with SPL for a given one-third octave band can be expressed by straight lines as shown in Figure B3.
(1) The slopes of the straight lines M(b), M(c), and M(d) and M(e);
(2) The intercepts of the lines on the SPL axis, SPL (b) and SPL (c); and
(3) The coordinates of the discontinuities, SPL (a) and log n(a); SPL (d) and log n = −1.0; and SPL (e) and log n = log (0.3).
(b) The important aspects of the mathematical formulation are:
(1) SPL " SPL (a) n = antilog [M(c)*(SPL-SPL(c))] (2) SPL (b) ≤ SPL < SPL (a)n = antilog [M(b)*(SPL-SPL(b))] (3) SPL (e) ≤ SPL < SPL (b)n = antilog [M(e)*(SPL-SPL(b))] (4) SPL (d) ≤ SPL < SPL (e)n = 0.1 antilog [M(d)*(SPL-SPL(d))] (c) Table B4 lists the values of the important constants necessary to calculate sound pressure level as a function of perceived noisiness.
EC28SE91.111 EC28SE91.112