Speech intelligibility is a measurement of the interaction between three components: the speech signal, the transmission channel, and the listener. Anything that interferes with any of these components can affect intelligibility. Vocal fry, though sometimes associated with vocal pathology, is commonly used in non-disordered speech. Speech produced with vocal fry differs from typical (modal) voicing in terms of pitch, volume, and quality. These differences may negatively impact intelligibility. Currently, no direct evidence exists regarding the impact of vocal fry on speech intelligibility. The purpose of the current study was to answer the research question: Does vocal fry affect the intelligibility of spoken words? We hypothesized that single words produced with vocal fry would be less intelligible than single words spoken in modal voice due to the acoustic characteristics and perceptions of vocal fry. To test this hypothesis, words spoken in both vocal fry and modal voice were collected and compiled to produce a standard intelligibility test procedure. Data from 26 listeners who completed the intelligibility test were analyzed in terms of intelligibility score and listening difficulty rating. The mean intelligibility score as a percentage of words correctly identified was 62.08% for words spoken with fry and 64.56% for words spoken with no fry. This difference was statistically significant. The mean listening difficulty rating was 4.98 for words spoken with fry and 4.56 for words spoken with no fry. This difference was also statistically significant. These results suggest that vocal fry does negatively impact speech intelligibility at the single word level. Decreased speech intelligibility may have numerous possible linguistic, social, and economic implications.
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