Anomalous loudness function for speech.

Abstract

It is known that a greater attenuation is required for judgments of half-loudness with speech than for half-loudness with steady-state sounds. This study explored the role of reverberation in the anomalous loudness function of speech. Comparison stimuli were prepared by electrical attenuation of the standard stimuli, keeping the proportion of reverberant to direct components fixed for any particular judgment. A total of 1110 subjects were tested with speech or with isolated speech sounds, using a single judgment procedure employed in earlier studies designed to minimize known experimental biases. Changes in reverberation produced profound changes in loudness functions. Estimates of the loudness of speech resemble estimates of acoustic perspective, both being based upon the ratio of direct to reverberant sound as well as the intensity of these components. Evidence indicates that judgments of half-loudness of speech (as well as half-loudness of isolated speech sounds, noises, and tones) are equivalent to estimates of the effect of doubling distance from listener to sound source: The anomalous loudness function for speech is attributable to the special role of reverberation with this stimulus. These conclusions are in agreement with the physical correlate theory of sensory intensity.