Perception of vocal tremor during sustained phonation compared with sentence context

Vocal tremor is an acoustical phenomenon characterized by relatively periodic modulations in fundamental frequency and intensity. Although vocal tremor is considered easier to perceive during sustained phonation than during connected speech, systematic comparison between these speech contexts has not been investigated. This investigation compared vocal tremor perception during sustained phonation and connected speech contexts.

This is a prospective, controlled study with randomized conditions.

Audio recordings from five speakers diagnosed with essential vocal tremor were used for this study. Twenty-four naive adult listeners rated the overall severity (ie, aberrance) of the voice and the degree of shakiness (ie, tremor) during sustained phonation of /i/. A different group of 21 naive adult listeners rated sentence stimuli consisting of two different sentences, one loaded with voiced and the other with voiceless speech sounds.

All speakers were rated by listeners to have similar levels of shakiness and overall severity during sustained phonation. However, significantly higher levels of shakiness and overall severity were perceived during sustained phonation than during sentence context. A nonsignificant trend was shown for higher average ratings for shakiness and overall severity on voice-loaded compared with voiceless-loaded sentences.

This study demonstrated that vocal tremor is perceived as significantly more severe during sustained phonation than during connected speech. More importantly, individual speakers differed in their ability to reduce vocal tremor perception during connected speech. Thus, sustained phonation does not necessarily offer a valid estimation of the impact of a vocal tremor on an individual's connected speech.