Dynamic acoustic evidence of nasalization as a compensatory mechanism for voicing in Spanish apraxic speech

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 wordinitial
stops. The results show that the two apraxic speakers produced prevoicing
in /b d g/ in only one third of the cases (correctly identified as ‘voiced’). In these
cases, however, they exhibited significantly longer prevoicing than control
subjects, and this longer voiced portion was closely related to a longer nasal
murmur. These results shed light on the compensation strategies used 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.