Identifying metrics to predict annoyance due to Mach-cutoff flight ground signatures

Abstract

Theoretically, Mach-cutoff flight under ideal atmospheric conditions could lead to boomless supersonic flight observed under the flight path on the ground. Such ideal atmospheric conditions refract the sonic boom waves upwards at the caustic line, so they do not reach the ground. This presentation describes the perception of the evanescent sound field below the flight path. The work investigates perceptual attributes and metrics related to these unique sounds. Annoyance and three other perceptual factors (“Thunderous,” “Rumbly,” and “Swooshing”) were analyzed through subjective testing using pair-wise comparison. Stimuli used were from recordings made during NASA’s “Farfield Investigation of No-boom Thresholds” (FaINT). Linear regression with principal component analysis indicated which perceptual factors contribute to annoyance, and stepwise regression identified candidate metrics for predicting annoyance. Traditional loudness metrics (i.e., weighted Sound Exposure Level) were analyzed alongside sonic-boom specific metrics (i.e., Perceived Loudness) and sound quality metrics (i.e., Sharpness). [Work supported by the U.S. Federal Aviation Administration Office of Environment and Energy through ASCENT, the FAA Center of Excellence for Alternative Jet Fuels and the Environment, Project 42 through FAA Award No. 13-C-AJFE-PSU under the supervision of Sandy Liu. Any opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the FAA.]