PHYSICAL Cn.lR.ICTlih'ISTICS 01- .lUPITfON 



59 



by feeling. Soiiiul waxes between these limits are more easily sensed 

 by audition. 2 



This suggests a rational way of defining and determining the two 

 frequency limits of audibility. Measurements of these limits which 

 have been made in the past are questionable because the intensity 

 factor has been neglected. At the lower limit of audibility the ex- 

 cursions of the diaphragm and ossicles of the middle ear are probably 

 so large that the nerves feeding these movable parts are stimulated. 

 This observation at low frequencies as indicated in this work lends 

 color to the hypothesis of otologists that abnormalities in the hearing 



5LN5AT10N ARLA5 (CHIO 



of low frequencies are due to pathological conditions in the middle 



ear. This point is probably related to the tests on flexibility of the 



ear drum or ossicular chain due to the application of air pressure as 



observed by otologists in examination. Loss of sensitivity at low 



frequencies is considered an indication of 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 sensation can' be assumed. The elliptical area between the two 



curves may then be taken to represent an area of sensation which is 



^ The extrapolation upward of the curve of minimum audibility is consistent 

 with some recent observations of Mr. C. E. Lane at the University of Iowa, Physi- 

 cal Review, May, 1922. 



