158 
PHYSICS: R. L. WEGEL 
Proc. N. a. S. 
mum audibility and the curve of feeling is his area of sensation. The 
area of sensation which is most utilized in the interpretation of speech 
is represented approximately by the shaded area in figures 1 and 2. (See 
"Analysis of the Energy Distribution in Speech," I. B. Crandall and D. 
MacKenzie, Phys. Rev., Mar. 1922.) It wih be seen that CHK retains 
about 50 or 60% of the normal amount of sensation. He hears and inter- 
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prets conversation with some difficulty. The CHK curves pass through 
the speech area. In order to make him hear well, the speech area must 
be raised to a higher level of intensity or loudness as indicated by the 
dotted curve. 
6. Importance of Various Intensities in Speech. — It is interesting to specu- 
late on how CHK interprets speech. It has been shown (H. Fletcher at 
Franklin Institute meeting Mar. 30, 1922) that the intensity of speech 
may be varied over perhaps 70-80% of the range of sensation without 
serious loss of intelligibility to the normal ear. As the sound intensity 
is decreased, the intelligibility drops very suddenly to zero at minimum 
audibility. A similar drop is to be expected at an intensity so loud as 
to be painful. It is evident therefore, that the range throughout which 
speech is intelligible for CHK is very considerably limited as compared 
to normal. It is possible to design a deaf set which increases the intensity 
of the principal speech region to any desired place within the abnormal 
sensation area and so in a measure compensate for this narrowed range. 
The region in figure 2 marked Region of Lesser Importance in Con- 
versation" corresponds to stimuli in conversation of lesser energy content 
such as the minor shadings and fainter consonant sounds. While it is 
