Abstract:

The auditory system must encode dynamic aspects of acoustic stimuli at frequencies throughout the audible spectrum. This coding is limited by the temporal resolution of the ear. Recent measures of modulation detection and temporal gap detection thresholds with narrow-band noises of fixed bandwidth indicate that temporal resolution does not vary with noise carrier frequency from 500 to 4400 Hz. The present study investigated temporal processing using a modified masking period pattern technique. Masked thresholds were measured for pure tones of 500, 2000, and 4000 Hz that were 400 ms in duration. Maskers consisted of narrow-band noises centered on the signal frequency that were either unmodulated or sinusoidally amplitude modulated (modulation depth=1.0) at frequencies from 4 to 256 Hz. The noise bandwidth ranged from 200 to 1600 Hz at each center frequency. By comparing masked thresholds for the unmodulated and amplitude modulated noises, one may assess both within-channel (narrowband noises) and across-channel (wideband noises) temporal processing. Preliminary results indicate that thresholds for a given masker bandwidth depend strongly on modulation frequency but vary little with signal frequency over the range tested. The data will be discussed relative to measures of temporal resolution and comodulation masking release.