Pitch of Periodic Pulses with Nonuniform Amplitudes
James L. Flanagan, Newman Guttman, Bernard J. Watson · The Journal of the Acoustical Society of America · 1962
Subjects, listening with ear-phones, adjusted the pitch of a uniform, periodic train of pulses to match the pitch of an experimental pulse pattern. One experimental pattern was periodic pulses with alternate amplitudes +a and +b. A second was similar but with alternate pulse amplitudes +a and −b. All pulse durations were 25 μsec. The parameters investigated, besides polarity pattern, were level difference ΔL=20 log |a/b| (0 to 20 db), and pulse rate (25 to 1074 pps). Results show that, roughly, for the (+a,+b) pattern a pulse-rate match is made for a ΔL less than 6 db, regardless of pulse rate. For ΔL greater than 10 db, a match of one-half pulse rate is made, also independent of pulse rate. For the (+a,−b) pattern, on the other hand, the pitch match is highly dependent both upon pulse rate and ΔL. As ΔL increases from 0 db, the match shifts away from the pulse rate at progressively lower frequencies. As in the first case, for ΔL>10 db, a pulse-rate match is never made. The amplitude and phase spectra of the stimuli are computed. The basilar-membrane displacements produced in the ear by the stimuli are simulated and examined. As in earlier experiments, the correlation between subjective behavior and membrane displacement is considered. Finally, the possible relationship of the results to the diplophonic voice is noted.