Rate discrimination of high-pass-filtered pulse trains.

Difference limens for trains of 30-microseconds pulses were determined for repetition rates of 50, 100, 200, 400, and 800 pulses per second under conditions of no filtering and high-pass filtering (115 dB/oct) with corner frequencies of 2.5, 5.0, 7.5, and 10 kHz. Low-pass-filtered noise was mixed with the trains of impulses to preclude discrimination on the basis of potential low-frequency signal components. Measures were obtained from four trained listeners at a signal level of 30 dB SL relative to individually determined thresholds for each filter condition and repetition rate. The data support the hypothesis that resolution of pulse-train repetition rate involves both temporal- and frequency-based processes--the latter becoming ineffective when frequency resolution of the ear is insufficient to resolve separate harmonics of the signal. Inter- and intra-individual differences are interpreted as reflecting frequency resolution capacity.