FREE VOICE AND PURE TONE AUDIOMETER FOR ROUTINE TESTING OF AUDITORY ACUITY: Studies on Comparative Efficiency

Abstract

THE tone audiogram is a complex one of many factors ; no final statement has yet been made by which the interpretation of either can be made in terms of the other or by which both can be reduced to a common denominator. Some laboratories depend exclusively on a pure tone audiogram as a measure of how well a man can hear speech, while others look askance on the pure tone test and claim that only a test using speech sounds is valid as a measure of speech reception.An early discussion of the relation between speech reception and audiometry is that of Fletcher,1 who compared a free voice test and audiometry through the speech range (512 to 2048 cycles per second).Fletcher concluded, from the rather close correspondence of hearing loss, that the free voice and the pure tone audiogram measure essentially the same auditory function. It is clear that on the basis of laboratory data there is empiric justification for attempts to equate the two tests in routine situations.

Methodological aspects of auditory threshold measurements.

“…The history of psychophysics reveals numerous attempts to establish the absolute intensive threshold for hearing. Recent research, however, has tended to augment these data with information on the variability of threshold measurements as a function of time (e.g., 2,6,11). The critical relevance of shifts in sensitivity in the formulation of modern theories of hearing has already been emphasized (3).…”

The emergence of a tonal sensation.

“…It is, however, quite possible to obtain precision at least twice as good as this even with the clinical audiometer (6), so that it would seem desirable in the laboratory to test auditory acuity using steps of two or even of one db. Now when the acuity of an ear is carefully examined by the use of these finer steps, with many stimuli presented at or very close to threshold, a phenomenon occurs which is ordinarily overlooked when larger intensity steps are used: a change in the quality of the tone seems to occur as the stimulus intensity increases.…”