PROCEEDINGS 
OF THE 
NATIONAL ACADEMY OF SCIENCES 
Volume 8 JULY 15. 1922 Number 7 
THE PHYSICAL EXAMINATION OF HEARING AND BINAURAL 
AIDS FOR THE DEAF 
By R. L. Wegeiv 
Research Laboratories of the American TeivEphone and Tei<Egraph Company 
AND THE Western Electric Company, Inc. 
Read before the Academy, April 25, 1922 
1. Introduction. — The function of the auditory sense is to detect sounds 
of various kinds and wave shapes varying over a range of pressure on the 
ear drum of from about .001 dyne to 1,000 dynes and over a considerable 
part of this range to differentiate with certainty between complex sounds 
so nearly alike that no existing physical apparatus can separate them. 
The binaural feature adds a sense of orientation with respect to a source 
and uniform sensitivity for sounds approaching from different directions. 
The abnormal auditory sense may be regarded as lacking more or less in 
(a) range of sensation (frequency and intensity); (b) quality of sensation 
in various regions of the range; (c) the binaural sense. Apparatus and 
methods have been developed by means of which the outstanding elements 
of these functions can be measured and to a limited extent compensated for. 
In a sense this paper prefaces a more detailed discussion of the audio- 
metrical and pathological phases of abnormal hearing which will be pre- 
sented next week by Dr. K. P. Fowler and the author before meetings of 
the American Otological Society and the American Rhinological, Laryngo- 
logical, and Otological Society. 
2. Minimum Audibility. — Figure 1 shows a plot of the minimum audible 
pressure on the average of 72 normal ears taken throughout a range of 
frequency of from 60 to 4,000 cycles. Both the intensity and frequency 
scales are logarithmic. This curve has already been published (The 
Frequency Sensitivity of Normal Ears, by H. Fletcher and R. L. Wegel, 
these Proceedings, January, 1922, and in the Physical Review). Although 
all skew errors in the determination of the average curve have not been 
eliminated, an investigation has shown that they are so small as not to 
effect the utility of the curve for the purpose of measuring deafness. Among 
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