The phonetic characteristics in patients of bilateral vocal fold paralysis without tracheotomy

Objectives. Patients with bilateral vocal fold paralysis (BVFP) theoretically have difficulty producing voiceless consonants. However, perceptual studies have revealed clear production of voiceless consonants with good articulation scores in nontracheostomized patients. The purpose of this study was to clarify the production of voiceless stops during articulation in patients with BVFP compared to normal speakers. Methods. The perceptual, acoustic, and aerodynamic characteristics of patients with BVFP and those with normal speech were investigated with special reference to voiceless stop consonants. Test words were prepared to place the stop consonants in different phonological environments, and were all nonsense words. Results. The patients with BVFP perceptually produced the three types of stops successfully. However, they acoustically varied voice onset time to produce phonetically representative stops but decreased voice onset time of /p^h/ and /p/ compared to those of normal speakers. These patients may properly control air pressure to produce the three types of stop consonants similar to normal speakers. Conclusion. The patients with BVFP realized the distinctions between the three types of stops similar to the normal speakers. Although vocal mobility was absent in the patients with BVFP, voice onset time, vowel duration, closure duration, and air pressure were similar to those of normal speakers.