Auditory feedback in the regulation of voice

Adult speakers participated in a spontaneous speech task in which the intensity of their auditory feedback through earphones was systematically manipulated over a 20-dB-SPL range. In Experiment I, Ss showed a statistically significant but slight tendency to decrease their vocal intensity as sidetone was amplified. The effect was greatest when subjects were instructed to attend to their sidetone and to compensate for any changes in loudness. In Experiment II, the same procedures were repeated except that 80-dB-SPL noise was added in the earphones. Addition of the noise resulted in considerably enhanced sidetone-amplification effects, even when Ss were instructed to keep their vocal level constant. In Experiment III, several levels of noise (0, 60, 70, 80 dB SPL) were used and it was noted that the greater the noise, the more substantial were the sidetone-amplification effects. In Experiment IV, subjects were instructed to talk either louder or softer than usual, with and without noise. The data from this last experiment indicate that it is the presence of the noise that enhances response to sidetone manipulations, and not simply the level at which the subjects are talking.