EMG biofeedback in the treatment of hyperfunctional voice disorders.

In this study, six patients who were judged to produce speech with excessive laryngeal tension participated in 14 30-min biofeedback training sessions. The EMG signal, measured by bipolar surface electrodes placed over the cricothyroid region, was amplified, integrated, and used to control the output of a voltage controlled oscillator (VCO) and a noise generator. A voltage comparator was used as a threshold device. Thus, the noise generator was activated when the EMG activity exceeded the value selected on the comparator, and the VCO was activated when the EMG signal was below threshold. The results demonstrated that three of the subjects reduced the laryngeal EMG activity used during speech production with a concomitant improvement in voice quality. The voice quality of the three remaining subjects was unchanged. Suggestions are made for modifying the equipment and procedures used in this study for routine clinical use of EMG biofeedback.