Changes in Voice Level Caused by Several Forms of Altered Feedback in Fluent Speakers and Stutterers

Speakers change the level of their voice when they listen to noise or hear their own speech amplified: When noise level is increased the voice becomes louder, whilst the response to speech amplification is a reduction of voice level. The question posed here is whether, when the level of various sounds concurrent with vocalisation is raised, the direction of the vocal level response is like that to the speaker's speech or like that to noise. Voice level was measured in response to speech, white noise, delayed auditory feedback, frequency-shifted speech, and noise created by an “Edinburgh masker”. Selection of these sounds was governed by the role they have played in the explanation and treatment of stuttering. Fluent speakers and stutterers increased voice level when played delayed auditory feedback, the Edinburgh masker, or white noise; they reduced the level slightly in the remaining conditions. These results are used to assess auditory feedback monitoring accounts of the speech behavior of fluent speakers and stutterers, and some implications for the treatment of stuttering are pointed out.