Time constants of pitch processing arising from auditory filtering

Abstract

This study uses rippled noise and ‘‘AABB’’ noise [Wiegrebe et al., J. Acoust. Soc. Am. 104, 2307–2313 (1998)] to investigate time constants associated with pitch processing in the auditory system. RN and AABB have identical long-term spectra and autocorrelations but they differ in their temporal dynamics. Previously, it was shown that, when the pitch of the stimuli is below about 350 Hz, listeners could discriminate broadband AABB from RN based on a pitch-strength difference. Here, the effect of frequency passband on the RN-AABB discrimination was investigated. In each 1-kHz band, discrimination performance decreased with decreasing delay (32–4 ms). As the center frequency increased from 0.5 to 4 kHz, the rate of decrease became smaller such that discrimination was still significant in the highest band with the shortest delay. Further experiments suggest that the RN-AABB discrimination and its frequency effects are based on pitch-strength differences. Auditory simulations suggest that integration of pitch information occurs in two stages comprising a short, frequency-dependent time constant of auditory filtering and a long, yet undetermined neural time constant separated by a nonlinear transformation, i.e., half-wave rectification. [Supported by the Medical Research Council, the ‘‘Prof. Dr. Ing. Erich Mueller-Stiftung’’ and the ‘‘Deutsche Forschungsgemeinschaft.’’]