Perstimulatory Fatigue as Measured by Heterophonic Loudness Balances

Abstract

Perstimulatory fatigue is the decrease in loudness of a steady auditory stimulus during its presentation. In the past it was measured by requiring a simultaneous dichotic loudness balance between two pure tones of the same frequency, one in each ear. Under these conditions the listener hears a single phantom sound whose localization depends upon the relative intensities of the two tones. The present investigation shows that the process of localizing the sound image in making the loudness balance is not critical to the occurrence of per stimulatory fatigue. Two principal conditions were compared. In the first, the frequency of the comparison stimulus was the same as that of the fatiguing stimulus. In the second, the comparison and fatiguing stimuli differed sufficiently in frequency so that the listener always heard two pure tones which he could correctly localize in the two ears. It is concluded that the amount of perstimulatory fatigue is very nearly the same under these two conditions. In the early phases of the present research it was suspected that the loudness balances were influenced by absolute judgments of loudness. A procedure was developed which precludes the formation of a single absolute standard of loudness. This method results in greater measured fatigue than the usual procedure.