Voiced and Voiceless Stops: Differences in VOT and Closure Length Produced by Italian Deaf Children

This experimental research investigated the production of the voiced and voiceless stops /b d g/ and /p t k/ in initial and intervocalic position by four Italian children affected by congenital and profound hearing loss. The behaviour of the glottal valve and supraglottal articulators as well as the temporal coordination between the glottal and upper airway mechanisms in stops were analyzed from an acoustic point of view. Because glottal vibrations were never detected during the oral closure of voiced stops, VOT and closure durations were measured. Differences in VOT duration seemed to be more relevant in characterizing the voiced/voiceless opposition for stops in initial than for those in intervocalic position. For intervocalic stops, if the closure durations differed across the voiced and voiceless cases the VOT values remained essentially constant, but if the closure durations were constant, the VOT values differed. This indicates that our subjects possess in their linguistic code the voiced/voiceless phonological opposition and consequently the task of the hearing teacher is of great importance.