THE RELATION BETWEEN THE HUMAN FREQUENCY-FOLLOWING RESPONSE AND THE LOW PITCH OF COMPLEX TONES

RONNY DALE CHAMBERS, Purdue University

Abstract

The objective of this study was to evaluate the role of the frequency-following response (FFR) in the perception of pitch. Specifically, the relation between the value of the low pitch of complex tones and the fundamental frequency of the FFR was examined. Subjects were four normal-hearing adults with extensive musical training. The experiment was conducted in four stages. Initially, a series of 6-component complex tones was synthesized and calibrated such that the components of adjacent tones in the series i = 0 to 10 shifted upward in frequency by (DELTA)f. Mean pitch matches to a comparison pure tone were obtained for these stimuli in the second stage to derive pitch-shift functions for each subject. The pitch percepts were studied for two reasons. First, it was important to assure that the nature of the pitch-shift functions for the four subjects were similar to those reported in previous studies. Second, the pitch values obtained in the second stage were an integral part of the third stage. The FFRs elicited by the complex stimuli which were most divergent in pitch for each subject, and by pure tone signals of equal pitch, were recorded in stage three. In the final stage, frequency analyses of the FFR records were performed to determine the correspondence between the fundamental frequency of the responses to complex tones and to pure tones of equal pitch. It was determined that the fundamental frequency of the FFRs elicited by complex tones did not vary consistently with frequency or pitch shift; the fundamental remained much closer to 200 Hz (the frequency with a period equal to the stimulus waveform). In addition, the fundamental frequency of the FFR to pure tones with pitch equal to that of the complex tones also approximated the stimulus waveform. It was concluded that the output of the neural mechanisms reflected in the FFR does not vary in a manner consistent with shift in the low pitch of complex stimuli.

Degree

Ph.D.

Subject Area

Audiology

COinS