SOME STANDARDIZING TESTS OF STERN’S TONE VARIATOR. 
BY R. II. SYLVESTER. 
The tone variator is a closed-tube sound producing’ instrument. It 
consists of a cylindrical brass bottle, the bottom of which is a piston 
controlled by a delicate cog-wheel mechanism. By means of this the 
depth of the bottle may be readily changed, thus varying the pitch. 
The sound is produced by a stream of .air directed across the mouth of 
the bottle through a tube set at the proper angle. A pointer attached 
to the piston’s setting gear indicates the pitch in terms of vibrations 
per second. 
The purpose of this study was to determine the reliability of the in- 
strument and how best to manipulate it. It seemed especially well 
suited for investigations in pitch discriminations. Stern, the inventor 
of the variator, in an article in Vol. XXX of Zeitschrift fur Psychol- 
ogic, gives a full description of it and a good general estimate of its 
practical value. In our conclusions we have not overlooked his esti- 
mates, but we have drawn every conclusion directly from records made 
by the variator itself. 
* The arrangement of apparatus finally hit upon is as follows : The 
stream of air is furnished by Whipple tanks. Their pressure is regu- 
lated by weights and by a screw clamp applied to the soft rubber 
carrying tube. A water manometer attached to this tube gives the 
pressure readings. For reading the pitch of the tone emitted, the ton- 
oscope is used, with a phonette for its receiving apiiaratus. This 
apparatus, though quite complicated, is easily managed by one opera- 
tor, and pitches to a small fraction of a vibration are read accurately. 
The variator was first tested as to its behavior under different pres- 
sures of the air stream. An increase of pressure causes a rise in pitch. 
This variation is greatest for light pressure. Thus, an average rise of 
6.79 vd. resulted from changing the pressure from 2 units to 3 units, 
while there was but 2.84 vd. rise when the pressure was increased 
from 3 units to 4 units. (A unit is one-fourth of the highest pressure 
that will produce a sound in the variator.) The variation with pres- 
