Pitch of iterated rippled noise

Abstract

Iterated rippled noise (IRN) stimuli are generated by a cascade of delay (d), gain (g), and add networks. The matched pitch of IRN stimuli was determined as a function of the type of network used to generate IRN stimuli, the delay (d = 2, 4, and 8 ms), the number of iterations (n = 1,2,3,4,6,8) of the delay and add networks, and whether the delayed noise was added (g = 1) to or subtracted (g = -1) from the undelayed noise. The matched pitch of IRN stimuli did not depend on the type of network. When g = 1 (addition), the matched pitch did not depend on the number of stages of iterations (n) and was always equal to the reciprocal of the delay (1/d). When g = -1 (subtraction), the match pitch depended on n. When n = 1, the matched pitch of IRN stimuli was ambiguous having two pitches in the region of 1/d +/- 10%. When n = 8, the match pitch was equal to 1/2d. This change in the pitch occurred between n = 2 and 6. The results are discussed in terms of spectral and temporal models of complex pitch processing. A temporal model based on autocorrelation was able to provide quantitative predictions for the pitch of these IRN stimuli. However, a spectral type of model can also account for the pitch of these IRN stimuli.