DETECTING PITCH-PULSE ASYNCHRONIES AND DIFFERENCES IN FUNDAMENTAL-FREQUENCY

A series of experiments investigated the detection of pitch-pulse asyn chronies (PPAs) and of differences in fundamental frequency (Delta F0' s) between two simultaneous ''formants,'' each of which consisted of a group of sinusoidal components spaced sufficiently closely in frequen cy to be incompletely resolved by the peripheral auditory system. For such stimuli, introducing a Delta F0 caused the pitch pulses of the tw o groups to become progressively more asynchronous at later and later parts of the stimulus. A comparison of the psychometric functions for the detection of Delta F0's and of (constant) PPAs suggested that list eners could, under some circumstances, detect Delta F0's from the resu lting asynchrony. Using an adaptive procedure, it was also shown that, for a range of F0's from 20 to 125 Hz, the threshold PPA was constant at about 2.5 ms. This relationship between PPA threshold and F0 diffe rs from that previously reported for the detection of envelope asynchr onies between pairs of sinusoidally modulated tones [e.g., Strickland et al., J. Acoust. Soc. Am. 86, 2160-2166 (1989)], which remain consta nt in degrees, rather than in ms. Further experiments investigated the role of onset asynchronies in the detection of PPAs and showed that, although an asynchrony between the first pitch pulse in each formant w as sufficient for near-asymptotic performance, listeners could still d o the task when this cue was removed. For the detection of Delta F0's, onset asynchronies also aided, but were not necessary for, discrimina tion.