Objectives: This study was performed to determine whether and how unilateral vocal fold paralysis (UVFP) affects the production and perception of voiced stop consonants as compared with unvoiced stops, and to analyze the phonetic effects of UVFP on the voicing feature.
Methods: Phonetic constructs pronounced by 7 male patients with UVFP and 5 normal male subjects were recorded. The 432 speech tokens consisted of intervocalic, prevocalic, and postvocalic stop consonants (/p/, /t/, /k/, /b/, /d/, /g/) in the vowel contexts /a/ and /i/. Perceptual consonant identification testing was performed with 5 voice and speech professionals as listeners. The type and frequency of errors made in consonant identification were analyzed. Spectrographic analysis was used to analyze acoustic cues.
Results: The rate of correct consonant identification was significantly lower for tokens pronounced by patients with UVFP (77.3% versus 97.6%, p = .0001) because of incorrect identification of the voiced consonants, frequently perceived as their unvoiced homologues. Confusion between dental and alveolar place of articulation for unvoiced stops was also noted.
Conclusions: Unilateral vocal fold paralysis alters the voiced-unvoiced stop consonant distinction and the dental-palatal stop consonant distinction in an experimental nonspeech context. This finding implies the existence of a phonetic handicap for patients with UVFP. Further studies should determine the effects of UVFP on global speech intelligibility.