Speech adaptation: an aerodynamic study of adults with a childhood history of articulation defects.

Three groups of subjects were studied; former lispers, persons with a history of /l/ or /r/ distortion, and normal subjects with no history of speech defects. All were normal-sounding adult speakers of English at the time of participation. Subjects were asked to wear an experimental removable dental prosthesis that provided 4 mm of thickness in the alveolar region. Measurements of oral air flow and intraoral pressure during the reading of sentence material were made, with the focus on the consonants /s/ and /t/. The sibilant /s/ was experienced as the greatest problem for speech adaptation, regardless of the type of former articulation defect. Both groups of subjects with a history of articulation defects showed evidence of slower adaptation and use of compensatory strategies for /s/. They tended as a group to have the same minimum airflow values for /s/ after 2 weeks of practice speaking with the prosthesis as after 1 day of practice. Aerodynamic calculation of the size of the constriction for /s/ also showed little or no change for most of the former speech-defective subjects. Evidence based on intraoral pressure indicated that particular effort was expended for /s/ even after 2 weeks of practice in speaking with the prosthesis.