Discrimination of Missing Pitch Pulses

The object of this experiment was to determine the discriminability of missing pitch pulses in synthesized vowel-like sounds. Pitch pulses were derived from samples of real speech. Individual pitch pulses were removed from certain parts of these pulse trains. A fixed vowel POVO-type synthesizer was then excited by these pulse trains, and listeners were asked, in an A–B test, to discriminate between the POVO excited by complete pulse trains and the POVO excited by pulse trains having missing pitch pulses. It was found that a single missing pulse in the middle of a sustained monotone could be easily discriminated. However, stimuli having missing pitch pulses near the onset of the utterance could not be discriminated from stimuli generated from complete pulse trains. Discriminability depended on the position of the missing pulse in the pulse train. Discriminability of missing pitch pulses also depended on the average pitch period, the rate of change of pitch periodicity, and the total stimulus duration.