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IOWA ACADEMY OF SCIENCE Voi,. XXVII, 1920 
THE IOWA PITCH RANGE AUDIOMETER 
C. C. BUNCH 
The ideal apparatus for measuring the acuity of the ear should 
enable one to determine the faintest audible sound at each and 
every pitch within the tonal range. It should be 'easily and 
quickly operated and should be permanently standardized. The 
Pitch Range Audiometer is an approach to this ideal. 
The essential parts of this audiometer are a variable frequency 
generator having a range of between 25 d.v. and 14,000 d.v., a 
motor for rotating this generator, a telephone receiver, and an 
electric tachometer for indicating the pitch of the tones produced. 
The complete range of tones is produced by varying the speed of 
the motor. Intensity measurements are secured by means of a 
small potentiometer with an empirically chosen increasing scale 
of 400 per cent installed in the circuit. 
The practical use of the instrument has been demonstrated and 
verified in the otological clinic. It was used in the army, vocational 
school in selecting radio operators. Unlimited opportunities are 
open for its use in the psychology of music, and for the basis of 
laboratory experiments, and other lines of practical scientific 
work. 
THE LOCALIZATION OF SOUND BY WAVE PHASE IN 
THE OPEN EAR 
HEjNRY M. HALVERSON 
Wave phase localization may be studied under normal condi- 
tions; i.e, without the aid of conductors to the ears. Our ap- 
paratus consists of two telephone receivers connected in series 
from the same source. If the receivers are so energized as to 
produce a pure tone, the observer, by closing one ear and moving 
the head carefully from one source to the other, (the side of the 
head parallel to the axis of the receivers) will experience a series 
of “highs” and “lows” in intensity. These points of maximum 
and minimum intensity correspond exactly to the points of rein- 
forcement and interference as obtain in the standing wave. 
If now the observer, withi both ears open, (the aural axis 
parallel with the axis of the receivers) moves slowly from one 
source to the other, he will be conscious of a median plane locali- 
zation for each one-half wave length that he advances. These 
