LAS EDIFICACIONES QUE SE EFECTUARÁN EN EL PREDIO CON EXPEDIENTE CATASTRAL 01-076-017, DE CONFORMIDAD CON EL REGLAMENTO DE ZONIFICACIÓN Y USOS DEL SUELO DEL MUNICIPIO DE

ANOPP predictions are made for the B737–800/CFM56–7B using the source noise modules identified in Table 2.5 and the flight procedure described above. The source noise from the engine and airframe are propagated to observers located 4 ft above the ground in accordance to the specifications for

Figure 2.8.—Predicted tone-weighted perceived noise level (PNLT) time history at approach certification point.

certification measurement procedure. Noise propagation effects accounted for include spherical spreading, Doppler shift and convective amplification, atmospheric attenuation, and ground reflections based on data for grass-covered ground. The propagated acoustic spectra for each noise component are predicted at (user specified time increments) half-second intervals at each measurement location. From these spectra, ANOPP computes the perceived noise level (PNL), tone-weighted PNL (PNLT), and EPNL noise metrics for the individual sources and for the total aircraft.

The predicted PNLT time histories and 1/3-octave band spectra at the certification approach, lateral sideline, and flyover observer locations are shown in Figure 2.8 to Fig- ure 2.13. The 1/3-octave band spectra results are only shown for the three polar emission angles θe = 45°, 90°, and 135°. For the approach flight segment, the PNLT time history predicted at the certification approach location is shown in Figure 2.8 and the associated 1/3-octave spectra at the three polar emission angles are shown in Figure 2.9. For polar angles prior to overhead (θe = 90°) the flap and slat noise dominates the airframe noise component. The engine sources are dominated by the fan inlet and discharge noise prior to and after the vehicle has passed overhead. The other engine noise components are minimal for the approach flight segment since the engine thrust is only at about 30 percent of the total available thrust. The PNLT time history predicted at the lateral sideline certification location is shown in Figure 2.10, and the associated 1/3-octave spectra at the three polar emission angles are shown in Figure 2.11. As expected, the engine noise sources dominate, particularly the jet and fan noise. The tonal character of the fan inlet can be seen in the PNLT time history by the spikes at polar angles less than 60°. The predicted results at the flyover location are shown in Figure 2.12 and

Figure 2.9.—Predicted sound pressure level (SPL) at approach certification point for three different polar directivity angles, θe. (a) 45°. (b) 90°. (c) 135°.

Figure 2.13. The trends are similar to those seen for the predictions at the lateral sideline location. The inlet fan noise dominates for polar angles less than θe = 90°, and the fan discharge and jet noise dominate for polar angles greater than θe = 90°.

Figure 2.10.—Predicted tone-weighted perceived noise level (PLNT) time history at lateral sideline certification point.

Figure 2.11.—Predicted sound pressure level (SPL) at lateral sideline certification point for three different polar directivity angles, θ_e. (a) 45°. (b) 90°. (c) 135°.

Figure 2.12.—Predicted tone-weighted perceived noise level (PNLT) time history for flyover (with cutback) condition.

Figure 2.13.—Predicted sound pressure level (SPL) at flyover (with cutback) location for three different polar directivity angles, θe. (a) 45°. (b) 90°. (c) 135°.

The predicted EPNL results for each noise component contributing to the total aircraft noise are shown in Figure 2.14 for each certification measurement location. To compare the relative importance of the component noise sources on an EPNL basis, the noise from each source (fan inlet, fan discharge, jet, core, etc.) is analytically flown past each certification observer (lateral sideline, flyover, and approach). The EPNL for each source is computed as the difference between the full-system EPNL and the EPNL determined with all but the source component of interest included. (This is done on a pressure-squared basis.) This technique reduces the effect of duration and directivity discrepancies. As expected the airframe noise is nearly equivalent to the engine levels on approach and the engine sources dominate during the takeoff flight segment. The capability to identify the contribution of individual noise components provides insight into the key noise mechanisms contributing to the overall noise levels.

Identification and reduction of these sources will allow for the development of quieter aircraft designs and flight procedures.

The predicted EPNL compared with certification measure- ments of this vehicle are shown in Figure 2.15 to Figure 2.17. The predicted results were made assuming the highest gross weight found for this vehicle and are indicated on the plots by the red square. These measurements were obtained from the FAA Web site and are the flight certification noise measure- ments obtained for Boeing 737–800 with CFM56–7B. The exact details of each vehicle configuration or engine operation are not known. The cause of the large scatter in the data, particularly for the lateral sideline and flyover locations can in part be attributed to model-type variations in the engine and airplane system, which cause differences in the measured certification noise. Airplane weight and thrust performance differences by type lead to changes in trajectory and throttle history, which can produce measured noise differences of the

Figure 2.14.—Predicted contributions from each noise component to total effective perceived noise level (EPNL) at the three certification points.

Figure 2.15.—Comparison of predicted effective

perceived noise level (EPNL) for B737–800/CFM56–7B and noise certification data of 73 certificated B737s equipped with CFM56–7B engines. Approach measurement location.

Figure 2.16.—Comparison of predicted effective

perceived noise level (EPNL) for B737–800/CFM56–7B and noise certification data of 73 certificated B737s equipped with CFM56–7B engines. Lateral sideline measurement location.

Figure 2.17.—Comparison of predicted effective perceived noise level (EPNL) for B737–800/CFM56–7B and noise certification data of 73 certificated B737s equipped with CFM56–7B engines. Flyover measurement location.

first order. Differences in engine model architecture, even within a family of engine type, lead to the different engine- type ratings and may cause a substantial change in emitted noise. However, these engineering design implementations are often impossible to model without access to company- proprietary information. Also it should be noted that the manufacturers have some latitude in how the aircraft is flown in the vicinity of the flyover microphone, whereas little or no latitude exists near the other certification points. Therefore, they are likely to operate in an optimal manner that differs from the nominal takeoff procedure assumed. This could also explain the overprediction for the flyover point. The predic- tions shown, however, were not tweaked, but were created based on best available inputs and then directly compared with the data shown in Figure 2.15 to Figure 2.17. With many of the inputs not known exactly, the ANOPP results are consid- ered fair to good in comparison with the data.