Examination of the low frequency limit for helicopter noise data in aviation environmental design tool and integrated noise model.

Abstract

The current Federal Aviation Administration (FAA) aircraft noise modeling tools, Aviation Environmental Design Tool (AEDT) and Integrated Noise Model (INM), do not consider noise below 50 Hz in their computations. This paper describes a preliminary study to determine the effect of including low-frequency data on the accuracy of AEDT/INM results. Expanded aircraft noise spectra containing one-third octave band data to 12.5 Hz were analyzed using methods adapted from AEDT/INM. Results from expanded spectral data are compared with results from the historical AEDT/INM spectral data (one-third octave band data from 50 Hz to 10 kHz). This comparison showed a range of differences, from increases in overall un-weighted sound pressure levels, to negligible changes in A-weighted and time audible metrics. These changes may be particularly important for helicopters, with dominant low-frequency rotor noise below 50 Hz. Following the comparison, the potential implementation of expanded spectral data in AEDT/INM is discussed.