Speakers naturally adopt a special "clear" (CLR) speaking style in order to be better understood by listeners who are moderately impaired in their ability to understand speech due to a hearing impairment, the presence of background noise, or both. In contrast, speech intended for nonimpaired listeners in quiet environments is referred to as "conversational" (CNV). Studies have shown that the intelligibility of CLR speech is usually higher than that of CNV speech in adverse circumstances. It is not known which individual acoustic features or combinations of features cause the higher intelligibility of CLR speech. The objective of this study is to determine the contribution of some acoustic features to intelligibility for a single speaker. The proposed method creates "hybrid" (HYB) speech stimuli that selectively combine acoustic features of one sentence spoken in the CNV and CLR styles. The intelligibility of these stimuli is then measured in perceptual tests, using 96 phonetically balanced sentences. Results for one speaker show significant sentence-level intelligibility improvements over CNV speech when replacing certain combinations of short-term spectra, phoneme identities, and phoneme durations of CNV speech with those from CLR speech, but no improvements for combinations involving fundamental frequency, energy, or nonspeech events (pauses).
This study described preliminary work with the Supplemented Speech Recognition (SSR) system for speakers with dysarthria. SSR incorporated automatic speech recognition optimized for dysarthric speech, alphabet supplementation, and word prediction. Participants included seven individuals with a range of dysarthria severity. Keystroke savings using SSR averaged 68.2% for typical sentences and 67.5% for atypical phrases. This was significantly different to using word prediction alone. The SSR correctly identified an average of 80.7% of target stimulus words for typical sentences and 82.8% for atypical phrases. Statistical significance could not be claimed for the relations between sentence intelligibility and keystroke savings or sentence intelligibility and system performance. The results suggest that individuals with dysarthria using SSR could achieve comparable keystroke savings regardless of speech severity.
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