Effect of Speaking over Background Noise on Acoustic Correlates of Normal Voice in Adult Females

Abstract

The effect of speaking over background noise on the normal voices of thirty adult female subjects was investigated. Subjects were randomly assigned into three groups of 10 in order to study the effect of speaking over noise and duration of speaking on fundamental frequency and fundamental frequency variability. Each subject performed a speaking-in-quiet task followed by 20 minutes vocal rest, before speaking for the same period of time over 80dBA white noise. Using a sound level meter to monitor their voice level, subjects were required to speak as loudly as would be necessary to be understood by another person in 80dBA background white noise. The subjects' productions of /i:/, /u:/ and /a:/ were recorded before and after the speaking-in-quiet task, and before and after the speaking-in-noise task. Fundamental frequency and fundamental frequency variability were examined acoustically using the Fast Fourier Transform (Connor, 1975). Fundamental frequency was found to be significantly elevated after speaking in noise indicating that a change in voice had persisted after the demand for increased vocal effort had ended. Fundamental frequency variability was not sensitive to this change. Previous studies have concentrated on the response of the vocal mechanism while speaking over the noise, and the relationship of this to voice disorders (Ferguson, 1955; Klingholz, 1974). Changes in voice that persist and can be measured acoustically after the need for increased vocal effort has ended, have not previously been considered. Some practical and theoretical implications of the study are discussed.