Compensatory mechanisms in apraxic speech. Preliminary acoustic evidence for the interaction between nasality and voicing

Abstract : This paper is concerned with the phonetic realization of the voicing contrast by two Spanish speakers with surgery-related apraxia of speech and two matched control speakers. Specifically, it examines whether speakers with AOS, widely reported to have a deficit in laryngeal control, use nasal leak as a compensatory mechanism aimed at facilitating the initiation of voicing in word-initial stops. The results show that apraxic speakers produce prevoicing in /b d g/ in only 1/3 of the cases (correctly identified as ‘voiced’). In these cases, however, they exhibit significantly longer prevoicing than control subjects; a longer voiced portion is closely related to a longer nasal murmur in the two apraxic speakers. These results suggest compensation strategies by apraxic subjects to achieve voicing. Differences in the intensity patterns of nasal and voiced stops indicate that apraxic speakers control the timing of velopharyngeal gesture, suggesting that apraxia is a selective impairment.