The Effect of White Noise on the Loudness of Speech of Assigned Average Level

Continuous recorded speech passages were presented against a background of white noise and against a quiet background. The effect of the noise on the loudness of speech was determined by having listeners adjust the level of speech heard in quiet to sound equal in loudness to an assigned average level of speech presented against selected levels of background noise. In general, it was found that (1) low noise levels produce a proportionately lower depression in the loudness level of speech than higher noise levels, (2) as a first approximation, however, the effect of noise on the loudness of speech is a function of the speech-to-noise ratio rather than of the level of the speech alone or of the noise alone, and (3) under none of the experimental conditions did white noise actually increase the loudness of speech (the “Egan effect”). The assumption that a given level of noise subtracts a constant number of loudness units from speech (regardless of the level of the speech) was found to be fairly adequate in describing the experimental results.