Abstract by Menley Stewart
S. Hales Swift
Physics and Astronomy
Using Perception to Determine Acoustic Shock Threshold
Crackle is believed to be a major contributor to annoyance from military jet engine noise. Crackle, hypothesized to be related to the presence of acoustic shocks, may contribute to annoyance through mechanisms not captured by current metrics. We have conducted a listening study to investigate crackle perception. This included categorical scaling tests in which the participants rated the amount of crackle in each signal according to five categories, from smooth noise/no crackle to intense crackle. These ratings give us the opportunity to find a perceptually based definition of an acoustic shock. To count shocks in a waveform, a time-derivative threshold must be chosen. A shock threshold based on the standard deviation of the probability density function of the waveform time derivatives is correlated with listener ratings, and a recommended acoustic shock definition is proposed.