Impact of syllable stress and phonetic context on the distribution of intermittent aphonia – University of Copenhagen

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Impact of syllable stress and phonetic context on the distribution of intermittent aphonia

Researchers: Jenny Iwarsson and Julie Fredsø Andersen

Intermittent aphonia is perceived as sudden interruptions of voicing in dysphonic voices. The aphonic instances occur in different voice disorders and typically reflect stiffness of the vocal fold mucosa, that may require an increased phonatory subglottal pressure. Research on perceptual and acoustic characteristics of intermittent aphonia is sparse. The aphonic instances have been described as unpredictable, but experience from voice therapy indicates a close linkage to respiration as well as type of speech sound preceding the vowel. Based upon theoretical principles of vocal fold oscillation initiation and phoneme production, this study aims to investigate the phonetic distribution of this phenomenon in connected speech. The overarching hypothesis is, that aphonic instances in dysphonic voices are not totally randomly appearing, but related to syllable stress and phonetic context. Such finding would confirm clinical experience and increase our knowledge about underlying mechanisms in intermittent aphonia. This may be relevant to aetiology, assessment tools and treatment of this type of dysphonia.

Recordings of 31 dysphonic subjects with intermittent aphonia reading a standard text were analysed. The standard text was phonetically transcribed and all vowels of the text were labelled and categorised with regard to syllable stress and character of the phoneme preceding the vowel. All aphonic vowels of the recordings were identified perceptually and the occurrence within each syllable category were analysed in per cent. Four different hypotheses were formulated, suggesting a higher occurrence of aphonic vowels:

1. in unstressed as opposed to stressed syllables, 2. following an unvoiced phoneme as opposed to a voiced phoneme, 3. following two or more unvoiced phonemes as opposed to one unvoiced phoneme, and 4. following aspirated stops /p,t,k/ as opposed to unaspirated stops /b,d,g/. The results will be reported.