Investigation of the use of lower frequency acoustic data in helicopter environmental noise modeling

摘要

The Federal Aviation Administration (FAA) aircraft noise modeling tools AviationrnEnvironmental Design Tool (AEDT) and Integrated Noise Model (INM) do not currentlyrnconsider noise below 50 Hz in their computations. This paper describes a preliminaryrnstudy to determine the effect of including low-frequency data on the accuracy ofrnAEDT/INM results. Expanded aircraft noise spectra containing one-third octave bandrndata to 12.5 Hz were analyzed using methods adapted from AEDT/INM. Results fromrnexpanded spectral data are compared with results from the historical AEDT/INM spectralrndata (one-third octave band data from 50 Hz to 10 kHz). This comparison showed a rangernof differences, from increases in overall un-weighted sound pressure levels (SPL), tornnegligible changes in A-weighted and Time Audible metrics. These changes may bernparticularly important for helicopters, with dominant low-frequency rotor noise below 50rnHz. Following the comparison, the potential implementation of expanded spectral data inrnAEDT is discussed.