Vol. 8, 1922 
PHYSICS: R. L. WEGEL 
157 
mum audibility in figure 1 will be seen to have been extrapolated to the 
points of intersection at high and low frequencies. The feeling sensation 
in the middle range of frequency is first a tickling sensation and then be- 
comes acutely painful as the loudness is increased. As the frequency is 
decreased the sensation of feeling becomes milder until at frequencies 
around 60 cycles it is sensible as a flutter, but still quite different from 
the sense of audition. As the frequency is still further decreased to a 
point where the hearing and feeling lines appear to intersect, it is difficult 
to distinguish between the sense of hearing and that of feeling. The 
low point of intersection of two normal curves of minimum audibility 
and feeling sense may therefore be taken arbitrarily as the lower tone 
limit of audibility. . For frequencies lower than this it is easier to feel than 
to hear the air vibration. For any one individual this point cannot be 
determined with accuracy on account of the variation in judgment, but 
can be determined by extrapolation. A similar intersection of the two 
curves occurs at some very high frequency. The extrapolation upward 
of the curve of minimum audibility is consistent with some recent ob- 
servations of Mr. C. E. Lane of the University of Iowa. This work will 
be published shortly in the Physical Review. 
This gives a rational way of defining the two frequency limits of audi- 
bility and suggest a method of making an accurate determination of them. 
Measurements of these limits which have been made in the past are ques- 
tionable because the intensity factor has been neglected. At the lower 
limit of audibility the excursions of the diaphragm and ossicles of the 
middle ear are probably so large that the nerves feeding these movable 
parts are stimulated and therefore the measurements at very low frequen- 
cies probably give data related to the pathological condition of the appa- 
ratus of the middle ear and this independently of the stimulation of the 
auditory nerve. This point is probably related to the tests on flexibility 
of the ear drum due to the application of air pressure as observed by otol- 
ogists in examinations. Otologists usually associate loss of sensitivity 
at low frequencies with obstructive deafness if there is no loss at high 
frequencies. 
5. Sensation Area. — From the combined standpoint of utility and logic 
the logarithmic relation between stimulus (pressure variation) and sensa- 
tion can be assumed. The elliptical area between the two curves may 
then be taken to represent an area of sensation which is characteristic of 
the normal ear. Any point within this area represents a definite auditory 
sensation in frequency and intensity. 
An abnormal ear may be regarded as having an area of sensation which 
is smaller than the normal area but included within it. Figure 2 is a 
plot of the minimum audibility of the right and left ears for a man (CHK) 
suffering from a catarrhal deafness. The area between this curve of mini- 
