Talker intelligibility across clear and sinewave vocoded speech

Abstract

Talker intelligibility was compared across clear and sinewave vocoded speech. Ten talkers (5 female) from the Midwest and Western dialect regions recorded samples of 210 meaningful IEEE sentences, 206 semantically anomalous sentences, and 300 MRT words. Ninety-three normal hearing participants provided open set transcriptions of the materials presented in the clear over headphones. Forty-one different normal hearing participants provided open set transcriptions of the materials processed with an eight-channel sinewave vocoder. Transcription accuracy was highest for clear speech compared to vocoded speech, and for meaningful sentences, followed by anomalous sentences and words for both conditions. Weak talker effects were observed for the meaningful sentences in the clear (ranging from 97.7% to 98.2%), but were more pronounced for vocoded versions (68.5% to 85.5%). Weak talker effects were observed for semantically anomalous sentences in the clear (89.4%-93.3%), but more variability was observed across talkers in the vocoded condition (54.4%–73.7%). Finally, stronger talker effects were observed for clear and vocoded MRT words (83.8%–95.6%, 46.3%–59.0%, respectively). Talker rankings differed across stimulus conditions, as well as across processing conditions, but significant positive correlations between conditions were observed for meaningful and anomalous sentences, but not MRT words. Acoustic and dialect influences on intelligibility will be discussed.