"Auditory Feedback" or "Sidetone"? The Effects On Speech Production and Intelligibility of Auditory Stimulation from the Larynx

Abstract

A distinction is proposed between auditory feedback effects and sidetone effects. Auditory feedback effects involve variations in self-hearing that are contingent upon initial speech behaviour. These effects impair speech. Sidetone effects involve variations in, or supplements to, self-hearing that are not contingent upon initial speech behaviour. Sidetones, in contrast to feedbacks, tend to enhance speech. However, the two have been conceptualized together by assimilating sidetone effects to feedback effects. This has led to a failure to recognize that sidetones can enhance, rather than impair, speech intelligibility. It is argued here that it is the contingency of the variation in the true feedbacks that makes them disruptive, while the noncontingency of the variation in the sidetones increases the overall level of auditory interference and enhances speakers' intelligibility as they try to overcome it. This proposition was tested by comparing contingent and noncontingent forms of a self-hearing variation, laryngeal self-hearing (LSH). LSH is obtained by recording the signal from laryngograph electrodes and returning it in audible form to the speaker. In Experiment I, phoneticians judged speech produced with contingent LSH to be more abnormal than speech with noncontingent LSH. In Experiment II, a panel of lay listeners found noncontingent LSH speech to be more intelligible than speech in a control condition that had no self-hearing variation. The two experiments are interpreted as giving support to the proposed distinction between feedbacks and sidetones.