On the Pitch of Periodic Pulses

Abstract

Human subjects adjusted the frequency of one periodic pulse train to match the pitch of another train fixed in frequency. Two modes of pitch perception were found. In the first mode, for pulse rates less than 100 pulses per sec. the pulse trains were ascribed a pitch equal to the number of pulses per second, regardless of the polarity pattern of the pulses. In the second mode, for fundamental frequencies in excess of 200 cps, the sounds were assigned a pitch equal to the fundamental frequency. Between these frequency regions a mode transition occurred in which the pitch judgments generally fell between the pulse-rate and fundamental-frequency values. An effort was made to correlate the psychophysical results with the displacement and derivative patterns observed with an electrical analog of the basilar membrane. The two pitch modes were found to be manifested in the mechanical operation of the cochlea.