Audibility of Group-Delay Equalization

This paper discusses the audibility of group-delay variations. Previous research has found limits as a function frequency for different test signals, but extracting tolerance group delay to help audio reproduction system designers is hard. study considers four critical three synthetic and one recorded, modified with digital allpass filters. The signals are filtered produce positive or negative peak covering most sensitive range from 500 Hz 4 kHz, without changing at other frequencies. ABX listening tests using headphones reveal thresholds each signal. perception highly dependent on signal, unit impulse pink signals. Negative variations more easily audible than ones. smallest mean threshold was $-$0.56 ms 0.64 delay, obtained impulse. smaller those in previous studies. A hi-hat sound decaying 60 dB 80 hides variation. variation difficult hear recorded castanet work demonstrates how response loudspeakers can be perceptually tested, leads better understanding systems should equalized avoid distortion.