Implementation of Accurate Atmospheric Sound Attenuation Calculations in Aircraft Noise Certification Processes

The paper introduces a new simplified method that calculates sound attenuation over the propagation path, addressing the limitations of the existing SAE ARP 866A method. The new method, based on the Volpe acoustic center's research, utilizes regression analysis of data derived from the ISO 9613–1 and ANSI SI.26-1995 standards. The paper delineates the integration of the SAE method into software for calculating aircraft Effective Perceived Noise Level (EPNL) and presents a comparative analysis of sound attenuation, sound pressure level, tone-corrected perceived noise level, and EPNL using the current calculation methodology. The results show that although both methods yield comparable sound attenuation from 50 Hz to 5 kHz, the SAE method exhibits significantly greater attenuation in the 6.3 kHz to 10 kHz frequency band. Furthermore, the SAE method can result in EPNL calculations that are, on average, 0.2 to 0.5 EPNdB higher than those obtained using the SAE 866A method under various noise certification testing conditions.