The contribution of certain acoustic vowel measures to the overall speech intelligibility

Th e primary aim of this research was to verify if the vowel space of Italian people with speech sound disorders was diff erent from that of typically developing people. Several acoustic metrics derived from vowels, such as VSA–3, FCR–3, VAI–3 F1–Ratio and F2–Ratio, were applied to three diff erent experimental groups: 1) individuals with Down Syndrome, 2) speakers with profound hearing loss, and 3) hearing subjects without any chromosomal condition. Th e results proved that impaired subjects displayed a reduced vowel space, both in the range of F1 and F2, a great overlap between vowels and low speech intelligibility when compared to typical speakers. All measures were able to diff erentiate subjects with speech disorders from controls. In contrast, FCR–3 and F1–Ratio failed to distinguish people with Down Syndrome from deaf individuals.