Effect of High Sound Levels on the Intelligibility of Speech in Noise
Irwin W. Pollack, J. M. Pickett · The Journal of the Acoustical Society of America · 1957
Word intelligibility tests were carried out with earphones at sound levels up to 130 db for several noise and speech spectra. In the absence of masking noise, little change in the intelligibility of isolated monosyllabic words was observed for over-all speech levels up to 130 db. With background noise, however, word intelligibility deteriorates with an increase in over-all level although the speech-to-noise (S/N) ratio was held constant. For the normal speech spectrum and white noise, the deterioration in intelligibility at high levels increases as the S/N ratio is decreased. Control tests demonstrate that the deterioration in intelligibility observed at high levels is not due to distortion in the equipment before the ear. In fact, peak clipping of the mixed signal at moderate sound levels produce less loss in intelligibility (as a function of decibels of peak clipping) than simply increasing the over-all sound level of the unclipped signal above a critical level.