Monaural Sensitivity to Dispersion in Impulses and Speech.

摘要

Little is known of the ear's phase sensitivity limits outside the well known fact that excessive dispersion in speech signals results in chirp-like sound quality. The limits of phase sensitivity may be determined in reference to the parameters of an idealized dispersion since phase shifts are nothing more than delays in the short-time spectra of a signal. A number of discrimination tests were conducted which contrasted standard stimuli with phase modified variants of the stimuli to determine the limits of phase sensitivity. The idealized dispersion was that of delaying a band of frequency components such that discriminability could be measured as functions of center frequency, bandwidth and delay. The stimuli used in the tests included an impulse, phonemes, words, and a sentence. Sensitivity to dispersion in impulses was shown to be dependent on intensity, center frequency, bandwidth, and dealy. Discrimination scores half way between chance and perfect performance were achieved for dispersed impulses with delayed bands of frequency components centered between 250 and 500 Hz and delayed between 0.0625 and 0.125 milliseconds. Sensation level of the stimulus pairs was 80 dB. The effect of bandwidth on discriminability appears to reach a plateau at 100 Hz, i.e., bandwidths of interest are less than 100 Hz.