UTAH ACADEMY OF SCIENCES 139 
THE VOICE TONOSCOPE. 
BY FRANKLIN O. SMITH. 
(Abstract). 
Many attempts have been made to measure the motor 
process involved in singing, reading and speaking. Ob- 
viously the unaided ear will not serve the purpose. At- 
tempts to measure these processes by means of graphic and 
photographic apparatus have failed because these instru- 
ments are too cumbersome and admit too many sources of 
error. What is required is a “simple, and at the same time 
accurate and ready means of measuring the pitch of tones 
produced by the human voice.’ 
The instrument which has been designed to solve this 
difficulty is appropriately called the tonoscope by its in- 
ventor, Professor C. E. Seashore. Although complicated in 
structure it is easy of manipulation and is sufficiently ac- 
curate for measuring the pitch and timbre of the voice in 
singing and speaking, 
The tonoscope consists essentially of a movable screen 
in the form of a drum, which turns on an axis at the rate of 
one revolution per second. By means of a small acetylene 
gas flame at the end of a speaking tube in front of the mov- 
ing screen the vibrations of the voice are reflected upon the 
screen. The tonoscope, therefore, works on the principle of 
stroboscopic vision, or the principle of moving pictures. 
This stroboscopic effect is produced by a unique meth- 
od. The screen is perforated by 1800 holes each 3.5 mm. 
in diameter and spaced with the highest possible accuracy. 
These holes are arranged in 110 parallel rows, each complet- 
ing the circumference of the drum in uniform spacings for 
each row. The number of holes increases, by one for each 
1Seashore. The Tonoscope Psychological Monographs. No. 69, pp. 
row, beginning with 110 holes, over one octave. 
As one sings a given tone, say “c,” the row of holes 
corresponding to the vibration frequency of this tone ap- 
pears to stand still while all the rows at the right of this 
one appear to move forward and all those at left appear to 
