Relative rates of growth of annoyance of impulsive and non-impulsive noises.

Twenty-nine people judged the relative annoyance of five variable level signals and 29 impulsive and non-impulsive fixed-level signals in an adaptive paired comparison study. Signals were presented for judgment as heard indoors in a facility capable of accurately reproducing the very low-frequency content of sonic booms. When the annoyance of sonic booms unaccompanied by rattle was compared with that of sounds containing more higher-frequency energy (an aircraft flyover and an octave band of noise centered at 1 kHz), the relative rate of growth of annoyance, as expressed in C-weighted SEL units, was nearly 2:1. In other words, to maintain subjective equality of annoyance, each increase in level of sonic booms had to be matched by nearly twice the increase in level of an aircraft flyover or an octave band of noise centered at 1 kHz. Relative rates of growth of annoyance of sonic booms accompanied by rattle and of non-impulsive sounds, including both low- (63-Hz octave band of noise) and high-frequency energy (1-kHz octave band of noise and an aircraft flyover), were closer to 1:1. Relative rates of growth of annoyance for sonic booms unaccompanied by rattle and low-frequency sounds (63 Hz) were also about 1:1. These differences in relative rates of growth of annoyance of impulsive and non-impulsive sounds are as plausibly attributed to their relative low-frequency content as to impulsiveness per se. It may therefore be more useful for some purposes to express the annoyance of impulsive signals and other environmental noises containing substantial low-frequency energy in terms of effective (duration-corrected) loudness level rather than commonplace ASEL or CSEL.