Production and perception of greek vowels in normal and cerebral palsy speech

This study investigates the perceptual consequences and differences in vowel production between cerebral palsy (CP) afflicted Greek speakers and their normal counterparts. Formant (F1 and F2) values for the five vowels of Modern Greek were extracted from productions of both male and female speakers in stressed and unstressed conditions. These same productions were presented to normal hearing Greek speakers for vowel identification. Aggregate vowel spaces constructed from the mean F1 and F2 values reveal that the male CP speakers’ productions more closely resemble normal female spaces than that of normal males, but has only a slight impact on reducing intelligibility. Unstressed vowel productions from female CP speakers reduced intelligibility most significantly, in particular for the vowel [o]. Significantly greater standard errors around formant means for the CP speakers’ unstressed vowel productions suggest these speakers have considerably more difficulty in controlling vocal tract shape when using less vocal effort. Introduction This is an experimental investigation of vowels in Greek as a function of mobility (intact versus cerebral palsy afflicted system), gender, stress and vowel category. There are five vowels in Greek ([i, e, a, o, u]) and their spectral characteristics have been described in Fourakis et al. (1999). That study examined Greek vowels as produced by male speakers under different conditions of tempo, stress, finding significant effects of these factors on most acoustic characteristics (F0, amplitude, and formant structure). However, there have been no published results on vowels produced by women. In addition, there are no data on speech produced by Greek persons with cerebral palsy (henceforth CP), male or female. Thus, the present investigation presents production data (formant frequencies) for two groups of speakers – normal and CP, and perception data (classification of the productions by persons with normal hearing). Recent results on this area are reported by Liu et al. (2005) for Mandarin Chinese. ITRW on Experimental Linguistics Athens, Greece August 28-30, 2006 ISCA Archive http://www.isca-speech.org/archive