Temporal pitch perception and the binaural system

Two experiments examined the relationship between temporal pitch land, more generally, rate) perception and auditory lateralization. Both used dichoti c pulse trains that were filtered into the same high (3900-5400-Hz) frequen cy region in order to eliminate place-of-excitation cues. In experiment i, a 1-s periodic pulse train of rate Fr was presented to one ear, and a pulse train of rate 2Fr was presented to the other. In the "synchronous'' condit ion, every other pulse in the 2Fr train was simultaneous with a pulse in th e opposite ear. In each trial, subjects concentrated on one of the two bina ural images produced by this mixture: they matched its perceived location b y adjusting the interaural level difference (ILD) of a bandpass noise, and its rate/pitch was then matched by adjusting the rate of a regular pulse tr ain. The results showed that at low Fr (e.g., 2 Hz), subjects heard two pul se trains of rate Fr, one in the "higher rate" ear, and one in the middle o f the head. At higher Fu (>25 Hz) subjects heard two pulse trains on opposi te sides of the midline, with the image on the higher rate side having a hi gher pitch than that on the "lower rate" side. The results were compared to those in a control condition, in which the pulses in the two ears were asy nchronous. This comparison revealed a duplex region at Fr>25 Hz, where acro ss-ear synchrony still affected the perceived locations of the pulse trains , but did not affect their pitches. Experiment 2 used a 1.4-s 200-Hz dichot ic pulse train, whose first 0.7 s contained a constant interaural time diff erence (ITD), after which the sign of the ITD alternated between subsequent pulses. Subjects matched the location and then the pitch of the "new" soun d that started halfway through the pulse train. The matched location became more lateralized with increasing ITD, but subjects always matched a pitch near 200 Hz, even though the rate of pulses sharing the new ITD was only 10 0 Hz. It is concluded from both experiments that temporal pitch perception is not driven by the output of binaural mechanisms. (C) 2001 Acoustical Soc iety of America.