Difference limens for vocal aperiodicities
Jody E. Kreiman, Bruce R. Gerratt · The Journal of the Acoustical Society of America · 2003
Although jitter, shimmer, and noise characterize all voice signals, recent data from a method of adjustment task suggest that these acoustic attributes do not all have equal perceptual importance. Listeners did not agree well with one another when asked to match the amounts of jitter or shimmer in a voice, although they did agree well in their matching responses to noise. Several explanations for this finding are possible. Listeners may be insensitive to differences in amounts of jitter and shimmer in a voice, so that difference limens are large relative to customary measurement resolution; or listeners may have difficulty separating jitter and shimmer perceptually from the composite noise component. To investigate these issues, we synthesized several series of stimuli with and without noise, and differing by steps in the amounts of jitter or shimmer present. Listeners heard pairs of these stimuli and were asked to respond whether stimuli were the same or different. Receiver operating characteristic analysis was applied to determine how listener sensitivity to jitter and shimmer varies. [Research supported by NIDCD.]