A Psychoacoustic Test for Urban Air Mobility Vehicle Sound Quality 2023-01-1107

This paper will describe a psychoacoustic test that was completed during the summer 2022 in the Exterior Effects Room (EER) at the NASA Langley Research Center. This test investigated whether sound quality metrics (tonality, sharpness, etc.) may be useful for predicting noise-induced annoyance to notional sounds of Urban-Air Mobility (UAM) vehicles (“air taxis”, perhaps). A suite of 137 short (5 second long) samples of UAM noise was synthesized based upon aeroacoustic predictions of a NASA reference UAM quadrotor aircraft under several flight conditions. The synthesizer had parameters that could change aspects of the sound such as, for instance, the blade-passage frequency, the balance of tonal rotor noise to broadband noise, and aspects of the motor noise. These parameters nonlinearly impacted sound quality in a way that created a spread of predictors both in synthesizer parameters and in sound quality metrics. 40 subjects listened to the sound suite in the EER and judged each sound individually on a standard scale of annoyance. This paper intends to cover background and motivation for the test, details of the design of the test and generation of the test stimuli, details of the test execution, a method for assigning equivalent loudness values to the results of the test, and basic results that can be gleaned from the data.