Rating the perception of jet noise crackle

Abstract

Crackle is a perceptual aspect of noise caused by impulsive acoustic shocks and observed in supersonic jets, including those from military aircraft and rockets. Overall and long-term spectral noise metrics do not account for the unique perception of crackle. Listening tests were designed to better understand perception of crackle and examine its relationship to physical noise metrics, such as skewness of the first time derivative of the pressure waveform, hereafter derivative skewness. It is hypothesized that as derivative skewness increases, the perception of crackle tends to increase. Two listening tests were conducted with 30 subjects to examine their perception of crackle. In the first test, subjects compared and ordered crackle-containing sounds. In the second test, category scaling was employed with subjects rating the crackle content with category labels: (1) smooth noise with no crackle, (2) rough noise with no crackle, (3) sporadic crackle, (4) continuous crackle, and (5) intense crackle. There is a high correlation between perception of crackle and derivative skewness. This five-point classification scheme appears to be an effective tool to measure crackle perception. These insights will help inform community noise models, allowing them to incorporate annoyance due to jet crackle. [Data courtesy of F-35 JPO.]