DISCRIMINATION OF INTER-AURAL DELAYS IN COMPLEX WAVEFORMS - SPECTRAL EFFECTS

Sensitivity to interaural delays in high-frequency waveforms was examined using amplitude-modulated signals. Carrier frequencies ranged from 2-6 kHz and modulation was varied from 50-550 Hz. The signals'' components were not harmonically related. As carriers exceed 3 kHz a broad region appeared (from 150-350 Hz of modulation) over which there was little change in sensitivity to interaural time differences in the modulation envelope. Signals with interaurally-discrepant carriers were more difficult to lateralize, but for carriers at and above 4 kHz, a region of constant performance was found as the interaural frequency difference is increased from zero. Variations in modulation depth were useful in approximating the sideband attenuation occurring as wideband signals were filtered by the human auditory system. This technique allows an assessment of the importance of critical bands in these phenomena.