Pitch of Periodic Pulses without Fundamental Component

Abstract

The pitch-matching experiment described at the previous meeting was extended to filtered stimuli. Listeners adjusted the frequency of an unfiltered periodic pulse-train to match the pitch of a train which was high-pass filtered to remove the fundamental component. The stimuli were three combinations of plus and minus pulses per fundamental period: (a) +; (b) +, −; (c) +, +, −, −. The interpulse interval was an integral divisor of the fundamental period. Before being filtered, the pulses were rectangular, equal in amplitude, and 0.1 msec in duration. Listening was done in quiet at a sensation level of approximately 45 db with earphones connected binaurally in phase. The results indicate that for fundamental frequencies less than about 50 cps the pitch ascribed to the filtered stimuli is equal the number of pulses per second, regardless of pulse polarity. For fundamental frequencies greater than about 500 cps, the pitch ascribed equals, or approaches, the frequency of the lowest component passing the high-pass filter. Matches in the range 50 to 500 cps tend to equate the fundamental frequencies of the filtered and unfiltered stimuli. Toward explication, the amplitude and phase spectra of the stimuli are considered, and an electrical analog of the basilar membrane is used in an effort to relate the subjective results to patterns of membrane displacement.