The perception of speech rate in non-manipulated, reversed and spectrally rotated speech reveals a subordinate role of amplitude envelope information

Abstract

Previous research suggests that the broad-band amplitude envelope (ENV) of speech is crucial for the perception of speech rate and timing. The present experiment tested this claim using non-manipulated and spectrally rotated speech (rotated around 2.5 kHz) with a bandwidth of 5 kHz which both contain identical ENV and reversed speech in which the temporal organisation of ENV is distorted. 44 listeners of Swiss German rated perceived speech tempo on a continuous scale reaching from “rather slow” to “rather fast” in 48 stimuli (4 sentences × 4 speakers × 3 signal conditions). Results revealed a significant effect of signal condition. Both reversed and spectrally rotated speech were perceived as significantly faster than clear speech but there was no difference between spectrally rotated and reversed speech. Results were consistent for all sentences and speakers. Results suggest that the intelligibility of the signal plays a higher role in the perception of speech rate than the presence of the ENV.