(b) That if an important tone has occurred the tone correction has been adjusted to the value it would have had if the tone had been recorded fully in a single one-third octave band.
a. Explanation
None
b. Supplemental Information
(1) Band sharing is discussed under section A36.4.4.2.
c. Procedures
None
198. Section A36.4.4 Maximum tone-corrected perceived noise level
199. Section A36.4.4.1
The maximum tone-corrected perceived noise level, PNLTM, must be the maximum calculated value of the tone-corrected perceived noise level PNLT(k). It must be calculated using the procedure of section A36.4.3. To obtain a satisfactory noise time history, measurements must be made at 0.5 second time intervals.
Note 1: Figure A36-2 is an example of a flyover noise time history where the maximum value is clearly indicated.
Note 2: In the absence of a tone correction factor, PNLTM would equal PNLM.
Figure A36-2: Example of Perceived Noise Level Corrected for Tones as a Function of Aircraft Flyover Time
200. Section A36.4.4.2
After the value of PNLTM is obtained, the frequency band for the largest tone correction factor is identified for the two preceding and two succeeding 500 ms data samples. This is performed in order to identify the possibility of tone suppression at PNLTM by one-third octave band sharing of that tone. If the value of the tone correction factor C(k) for PNLTM is less than the average value of C(k) for the five consecutive time intervals, the average value of C(k) must be used to compute a new value for PNLTM.
a. Explanation
This section specifies the method of accounting for the effects of the suppression of tones occurring at or near the band edges of one-third-octave-band filters when determining a tone correction factor at the time of PNLTM.
b. Supplemental Information
(1) Band Sharing Adjustment Concept: The one-third-octave-band filtering process specified for analysis of airplane noise certification data may allow the tone-correction procedure presented in section A36.4.3 to under-predict a tone correction factor when the frequency of a tone is located at or near the edge of one or more one-third-octave bands. To account for this phenomenon, a band sharing adjustment is computed that takes advantage of the fact that, as a result of the Doppler Effect, a tone that is suppressed at PNLTM will probably appear normally in the spectra that occur before or after PNLTM. By averaging the tone correction factors calculated for the spectra within a 2-second period around PNLTM, the tone correction factor that would have occurred at PNLTM if it were not suppressed can be reasonably estimated.
c. Procedures
(1) Computation of Band Sharing Adjustment: Although part 36 refers to identification of the frequency bands in which maximum tone-corrections occur for the records near PNLTM, the presence or absence of band-sharing cannot be established merely by observing these frequencies. Even though the maximum tone that occurs in a one-third-octave band spectrum may not be related to the band of maximum tone-correction in the PNLTM spectrum, a related tone may still be present. Therefore, the average of the tone-corrections of all spectra within 1-second (five one-half second data records) of PNLTM must be used regardless of the bands in which maximum tones are found. If the band sharing adjustment is believed to result from effects other than band sharing, the applicant must demonstrate its absence for each event.
(2) Adjustment of PNLTM for Band Sharing: The band sharing adjustment must be computed before the determination of the 10 dB-down period and must be included in the reported PNLTM and EPNL values for the test condition data.
(3) Application of Band Sharing Adjustment for Simplified Procedure: When the simplified procedure is used to adjust data to reference conditions, the bandsharing adjustment, must be applied to the PNLTr at time of PNLTM before “delta 1" and EPNLr is calculated.
(4) Application of Band Sharing Adjustment for Integrated Procedure: When the integrated procedure is used to adjust data to reference conditions, a new band sharing adjustment must be calculated from the five data records for the one-third-octave-band spectra (adjusted to reference conditions) encompassing the PNLTr at time of PNLTM (this includes two data records prior to PNLTr at time of PNLTM, the PNLTr at time of PNLTM record, and two data records after PNLTr at time of PNLTM).
201. Section A36.4.5 Duration correction
202. Section A36.4.5.1
The duration correction factor D determined by the integration technique is defined by the expression:
PNLTMdt 2 t 1 t 10 PNLTantilogT1log10D -œœœßøŒŒŒºØ ò÷łöçŁæ= ÷łöçŁæ ÷łöçŁæ
where T is a normalizing time constant, PNLTM is the maximum value of PNLT, t(1) is the first point of time after which PNLT becomes greater than PNLTM-10, and t(2) is the point of time after which PNLT remains constantly less than PNLTM-10.
203. Section A36.4.5.2
Since PNLT is calculated from measured values of sound pressure level (SPL), there is no obvious equation for PNLT as a function of time. Consequently, the equation is to be rewritten with a summation sign instead of an integral sign as follows:
( ) PNLTM10 kPNLTlogt.antiT1log10D td 0k -œßøŒºØ ÷łöçŁæ= å=D D
where Dt is the length of the equal increments of time for which PNLT(k) is calculated and d is the time interval to the nearest 0.5s during which PNLT(k)remains greater or equal to PNLTM-10.
204. Section A36.4.5.3
To obtain a satisfactory history of the perceived noise level use one of the following:
(a) Half-second time intervals for Dt; or
(b) A shorter time interval with approved limits and constants.
205. Section A36.4.5.4
The following values for T and Dt must be used in calculating D in the equation given in section A36.4.5.2:
T = 10 s, and
Dt = 0.5s (or the approved sampling time interval).
Using these values, the equation for D becomes:
( ) 13PNLTM10 kPNLTlogantilog10D d2 0k --œßøŒºØ= å=
where d is the duration time defined by the points corresponding to the values PNLTM-10.
a. Explanation
None
b. Supplemental Information
(1) EPNL Equations: The equation for the duration correction, D, as shown in A36.4.5.4, is valid only for records of one-half second in length. The constant value 13 is used to normalize the one-half second values to the 10-second standard duration (10*log10 (10 seconds of ½ -second data records = 20 records) =13.01).
c. Procedures
None
206. Section A36.4.5.5
If in using the procedures given in section A36.4.5.2, the limits of PNLTM-10 fall between the calculated PNLT(k) values (the usual case), the PNLT(k) values defining the limits of the duration interval 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.
a. Explanation
This section specifies a requirement to calculate a duration correction, D, which is determined by means of integrating (summing) the PNLT values within 10 dB of PNLTM.
b. Supplemental Information
None
c. Procedures
(1) Identification of the First and Last Records Within the 10 dB-Down Period: When identifying the records that define the limits of the 10 dB-down period, those records having PNLT values closest to the actual value of PNLTM-10 dB must be used. As a result, the PNLT values for the PNLTM-10 dB points may not always be greater than or equal to PNLTM-10 dB.
(2) Calculation of the Duration Correction, D: When calculating the value of D, the full PNLT value and duration of each record within the 10 dB-down period must be included. Interpolation of discrete PNLT values to the exact point of PNLTM-10 dB is not allowed.
(3) Recorded Data: If recorded data do not encompass the entire 10 dB-down period, an EPNL cannot be calculated from those data, and the event must not be used for aircraft noise certification purposes.
207. Section A36.4.6 Effective perceived noise level
208. Section A36.4.6
The total subjective effect of an airplane noise event, designated effective perceived noise level, EPNL, 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 using the procedures given in sections A36.4.2, A36.4.3, A36.4.4 and A36.4.5.
209. Section A36.4.7 Mathematical formulation of noy tables
210. Section A36.4.7.1
The relationship between sound pressure level (SPL) and the logarithm of perceived noisiness is illustrated in Figure A36-3 and Table A36-3.
211. Section A36.4.7.2
The bases of the mathematical formulation are:
(a) The slopes (M(b), M(c), M(d) and M(e)) of the straight lines;
(b) The intercepts (SPL(b) and SPL(c)) of the lines on the SPL axis; and
(c) 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).
212. Section A36.4.7.3 Calculate noy values using the following equations:
(a) ( ) ( ) ( ) [ ] { }
SPL SPL antilog SPL SPL ≥ = − a n M c c
(b) ( ) ( ) ( ) ( ) [ ] { }
SPL SPL SPL antilog SPL SPL b a n M b b £ < = −
(c) ( ) ( ) ( ) ( ) [ ] { }
SPL SPL SPL antilog SPL SPL e b n M e e £ < = − 0 3 .
(d) ( ) ( ) ( ) ( ) [ ] { }
SPL SPL SPL antilog SPL SPL d e n M d d £ < = − 0 1 .
213. Section A36.4.7.4
Table A36-3 lists the values of the constants necessary to calculate perceived noisiness as a function of sound pressure level.
a. Explanation
This section specifies a requirement for using table A36-3 constants to calculate perceived noy values related to sound-pressure-level values.
b. Supplemental Information
None
c. Procedures
None
Siope = M(c) SPL(a), log n (a) Logarithm perceived noisiness, log n SPL(d) Slope - - M(b) SPL(C) SPL(b) Sound pressure level SPL М(e) Slope = SPL(e), log(0.3) M(d) Slope
- 1.0 Figure A36-3: Perceived noisiness as a function of sound pressure level Page 115
BAND SPL SPL SPL SPL SPL HZ (a) (b) (c) (d) (e) M(b) M(c) M(d) М(e) 1 50 91.0 64 52 49 55 0.043478 0.030103 0.079520 0.058098 63 85.9 60 51 44 51 0.040570 0.068160 80 87.3 56 49 39 46 0.036831 0.052288 4 100 79.9 53 47 34 42 0.059640 0.047534 5 125 79.8 51 46 30 39 0.035336 0.053013 0.043573 6 160 76.0 48 45 27 36 0.033333 7 200 74.0 46 43 24 33 0.040221 250 74.9 44 42 21 30 0.032051 0.037349 9 315 94.6 42 41 18 27 0.030675 0.030103 0.034859 10 400 40 40 16 25 0.030103 500 40 40 16 25 12 630 40 40 16 25 13 14 1 000 800 40 40 40 40 16 16 25 25 NOT APPLICABLE 0.053013 15 1 250 38 38 15 23 0.030103 0.059640 0.034859 16 1 600 34 34 12 21 0.029960 0.053013 0.040221 17 2 000 32 32 9 18 0.037349 18 2 500 30 30 15 0.047712 0.034859 19 3 150 29 29 4 14 20 4 000 29 29 5 14 0.053013 21 5 000 30 30 6 15 0.034859 22 6 300 00 31 31 10 17 0.029960 0.068160 0.037349 23 8 000 44.3 37 34 17 23 0.042285 0.029960 0.079520 24 10 000 50.7 41 37 21 29 0.059640 0.043573 Table A36-3: Constants for mathematically formulated noy values.
214. Section A36.5. Reporting of Data to the FAA
215. Section A36.5.1 General
216. Section A36.5.1.1
Data representing physical measurements and data used to make corrections to physical measurements must be recorded in an approved permanent form and appended to the record.
217. Section A36.5.1.2
All corrections must be reported to and approved by the FAA, including corrections to measurements for equipment response deviations.
218. Section A36.5.1.3
Applicants may be required to submit estimates of the individual errors inherent in each of the operations employed in obtaining the final data.
a. Explanation
None.
b. Supplemental Information
(1) Compliance Records: For compliance with section A36.5.1.1 through A36.5.1.3, all data measured during noise certification testing, including all time histories of physical measurements, noise recordings, instrument calibrations, etc., are to be recorded in permanent form and made available to the FAA for review, inspection, and approval. A common procedure is for the applicant to submit representative samples of test data for each noise measurement point and adjustments to measured data to permit the FAA to determine compliance with the regulation. The applicant may either: 1.) submit the complete test records along with the required corrections, or 2.) when approved by the FAA, the applicant may instead submit samples of test data along with the required data adjustments.
c. Procedures
(1) Test Records: All test records are to be submitted to the FAA for compliance review and approval. Adjustments to the measured data are also to be submitted to the FAA for review and approval. The FAA may require an applicant to submit records showing estimates of the magnitude of potential errors at each step in the measurement, analysis, and adjustment of data. Specific data-reporting requirements are identified in section A36.5.2.
219. Section A36.5.2 Data reporting
An applicant is required to submit a noise certification compliance report that includes the following.
a. Explanation
None.
b. Supplemental Information
(See section 36.1501(a))
c. Procedures
None
220. Section A36.5.2.1
The applicant must present measured and corrected sound pressure levels in one-third octave band levels that are obtained with equipment conforming to the standards described in section A36.3 of this appendix.
221. Section A36.5.2.2
The applicant must report the make and model of equipment used for measurement and analysis of all acoustic performance and meteorological data.
222. Section A36.5.2.3
The applicant must report the following atmospheric environmental data, as measured immediately before, after, or during each test at the observation points prescribed in section A36.2 of this appendix.
(a) Air temperature and relative humidity;
(b) Maximum, minimum and average wind velocities; and
(c) Atmospheric pressure.
223. Section A36.5.2.4
The applicant must report conditions of local topography, ground cover, and events that might interfere with sound recordings.
224. Section A36.5.2.5
The applicant must report the following:
(a) Type, model and serial numbers (if any) of airplane, engine(s), or propeller(s) (as applicable);
(b) Gross dimensions of airplane and location of engines;
(c) Airplane gross weight for each test run and center of gravity range for each series of test runs;
(d) Airplane configuration such as flap, airbrakes and landing gear positions;
(e) Whether auxiliary power units (APU), when fitted, are operating for each test run;
(f) Status of pneumatic engine bleeds and engine power take-offs for each test run;
(g) Indicated airspeed in knots or kilometers per hour for each test run;
(h) Engine performance data:
(1) For jet airplanes: engine performance in terms of net thrust, engine pressure ratios, jet exhaust temperatures and fan or compressor shaft rotational speeds as determined from airplane instruments and manufacturer's data for each test run;
(2) For propeller-driven airplanes: engine performance in terms of brake horsepower and residual thrust; or equivalent shaft horsepower; or engine torque and propeller rotational speed; as determined from airplane instruments and manufacturer's data for each test run;
(i) Airplane flight path and ground speed during each test run; and
(j) The applicant must report whether the airplane has any modifications or non-standard equipment likely to affect the noise characteristics of the airplane. The FAA must approve any such modifications or non-standard equipment.
a. Explanation
This section specifies the noise certification data-reporting requirements.
b. Supplemental Information
(1) Applicant's Reporting Requirements: Following are items that the applicant also must report in meeting the requirements of sections A36.5.2.1 through A36.5.2.5:
(i) Test conditions throughout the 10 dB-down period, including test airspeed, engine performance parameters, and airplane flight path position.
(ii) Recorder sampling rates.
(iii) Airplane and engine performance information, including airplane altitude and climb angle.
Any other parameters that may affect the measurement or adjustment of acoustical, airplane, or engine performance data must also be recorded throughout the 10 dB-down period (e.g., SBV position, CG position).
c. Procedures
None
225. Section A36.5.3 Reporting of noise certification reference conditions.
226. Section A36.5.3.1
Airplane position and performance data and the noise measurements must be corrected to the noise certification reference conditions specified in the relevant sections of appendix B of this part.
The applicant must report these conditions, including reference parameters, procedures and configurations.
a. Explanation
This section specifies a requirement to report reference conditions, parameters, procedures, and configurations used for noise certification testing.
b. Supplemental Information
(1) Reference Conditions: Reference conditions are specified under section B36.7.
(2) Equivalent Procedures: FAA does not approve equivalent procedures for noise certification reference conditions.
(3) DER Information: Reference airplane performance is to be FAA approved based on approved data. This may require that a flight analyst DER with appropriate authority for part 36 reference airplane performance submit completed FAA Form 8110-3 for review by the approving FAA flight test branch of the ACO.
(See the DER Guidance Handbook, reference 10 for additional information.)
c. Procedures
None
227. Section A36.5.4 Validity of results.
228. Section A36.5.4.1
Three average reference EPNL values and their 90 per cent confidence limits must be produced from the test results and reported, each such value being the arithmetical average of the adjusted acoustical measurements for all valid test runs at each measurement point (flyover, lateral, or approach). If more than one acoustic measurement system is used at any single measurement location, the resulting data for each test run must be averaged as a single measurement. The calculation must be performed by:
(a) Computing the arithmetic average for each flight phase using the values from each microphone point; and
(b) Computing the overall arithmetic average for each reference condition (flyover, lateral or approach) using the values in paragraph (a) of this section and the related 90 per cent confidence limits.
229. Section A36.5.4.2
For each of the three certification measuring points, the minimum sample size is six. The sample size must be large enough to establish statistically for each of the three average noise certification levels a 90 per cent confidence limit not exceeding ±1.5 EPNdB. No test result may be omitted from the averaging process unless approved by the FAA.
Note: Permitted methods for calculating the 90 per cent confidence interval are shown in the current advisory circular for this part.
a. Explanation
Appendix 1 of the appended TM describes methods for calculating 90 per cent confidence intervals
b. Supplemental Information
None
c. Procedures
None
230. Section A36.5.4.3
The average EPNL figures obtained by the process described in section A36.5.4.1 must be those by which the noise performance of the airplane is assessed against the noise certification criteria.
a. Explanation
This section specifies that average values of EPNLr (effective perceived noise level adjusted for reference conditions) for the flyover, lateral and approach noise measurement points are to be within a 90 percent confidence interval limit of ±1.5 dB. Both the mean EPNL levels and the associated confidence intervals are to be reported.
b. Supplemental Information
(1) Average EPNLr Levels: The average values of EPNLr are to be reported in a noise certification compliance document for flyover, lateral, and approach. The average value of EPNLr for n clustered data points, L1, L2, - - - -, Ln, is: Lmean = (L1 + L2 + - - - + Ln)(1/n). The average value of EPNLr from an NPD database is the noise level determined along the regression line through the adjusted data set at the appropriate thrust (power)