Interaural pitch perception difference: dependence upon internal and external factors.

Tone pulses were presented consecutively to one and the other ear in normally hearing musicians. The frequency of pulses in one, reference ear was fixed. That in the other, test ear varied to achieve the same pitch of tones in both ears. The frequency deviation of the test tone from the reference one was judged as the interaural pitch perception difference, IPPD. No dissimilarities in IPPDs were found between females and males. On the other hand, in both genders the IPPD scores were greater at higher than at medium and, especially, at lower tone frequencies, 2000, 1000, and 500 Hz, respectively. Also, the IPPDs displayed greater values when the reference tone was administered to the left ear, while the right ear served for the application of the test tone, LrRt, than when the reference tone was delivered to the right ear, while the test tone was applied to the left ear, RrLt. The IPPD differences under LrRt and RrLt stimulus presentations modes were prominent just at higher than at medium and, especially, at lower tone frequencies. The results are interpreted proceeding from the peculiar coding of low- and high-frequency acoustic information into brain auditory structures. Correspondingly, the IPPD is considered to be a consequence of central neural rather than of peripheral receptor events.