The emergence of a tonal sensation.

Abstract

Abstract : When the absolute threshold of auditory acuity for pure tones is carefully explored with fine intensity steps, a region called the 'zone of detectability' can be noticed by experienced subjects. In this zone, pure tones can be detected but cannot be said to have a true pure-tone quality. This zone of detectability is defined as the intensity area between a 50% detection threshold and a 50% pure-tone threshold. Two thresholds were simultaneously determined at each of 6 frequencies, 500, 1000, 2000, 4000, 8000, and 14000 cps. Two experienced subjects were used. The zone of detectability varied at random from 2-4 db independent of frequency. It was shown that particularly for the higher frequencies, an experienced subject can select a certain criterion of tonality and maintain it with considerable precision. The subject matched a variable frequency of very low sensation level to a standard frequency of 10 db sensation level. The frequency-match was progressively better as the intensity increased from 0 to 10 db sensation level, and the course of this improvement was taken to symbolize the gradual nature of the emergence of a tonal sensation from an indefinite 'something' to the sharp sensation of a clear pure tone. It was reasoned that the subjective criterion of 'tonality' which a subject can select and maintain is indeed one of pitch rather than of loudness; but it was concluded that the phenomenon depends upon the intensity of the stimulus rather than upon a change in its frequency-composition.