PHYSICAL MEASUREMENTS OP AUDITION 



159 



From the discussion above it was seen that the number of tones 

 corresponding to any region was approximately proportional to the 

 area of that region when the logarithmic units were used. Conse- 

 quently the per cent.* of hearing can be taken as the fractional part 



'•8 16 32 64 128 256 SI HHffl»««KB8fiK8 / r,. , L ea a 



300 400 500 600 100 BOO 900 WOO 1100 1200 WW) 1500 p lt ch y 



A 16 32 64 128156 512 MflW840*( 



Frequency 



A- Hearing =94% 



3C0 400 500 f00 '00 000 900 1000 "00 1/00 UM « W0 P.tch 



B-Heanna = 6H 



$000 



lioo 

 $ w 



*000l, 



60 S 



40 J 

 10^ 



20 i 



40 I 



8 i6 32 64 I2b 256511 m*2MmW mm F„ Ruency 

 300 W0 500 600 700 000 500 1000 1100 W HOC M0 H00 P,tch 



C-Hearina = 74l° 



^000* 



'8 16 51 64 128 256 511 lvtiunoTHxionLnxpxia}Fi. eQuenC y 

 300 400 500 600 700 800 300 1000 1100 1200 1X0 1400 1500 p, ,^t. 



D~ Hearing = 58 c /o 



- 8 16 31 64 \B2%5\immmi.i!^yML 

 300 400 500 W0 700 000 300 1000 H00 UK M i-W 1500 Pitch * 



E~ Hearing -IZ°J° 



Fig. 7 



"W0I. 



60 fc 



■40 § 

 20 5 

 X 

 20 | 

 40 2 

 60" 



8 16 32 64 13 » « PMWWtiMilf™ .., 

 JO0 W0 500 600 >00 «0O 300 1000 1100 UKiXO i«00 1500 p,, c >, ' 



F-Hearmg = 40lo 



Audiograms for Typical Cases ofjDeafness 



of the normal auditory-sensation area in which tones can be properly 

 sensed. The per cent, of deafness is, of course, 100 minus the per 

 cent, of hearing. 



To emphasize the meaning of this definition, some audiograms, 

 that is minimum audible intensity curves, for some typical cases of 

 deafness will be given. These are shown in Fig. 7. The first chart 



* This assumes that the Fechner ratio for pitch and loudness is approximately the 

 same for one having abnormal as for one having normaljiearing. 



