Tone variator

The instrument consists of an adjustable brass resonator, which is supplied with a constant flow of air across the opening at the top.

Turning a graduated cam on the front of the apparatus raises or lowers a piston in the bottom of the resonator, changing the volume of its interior, thus altering the sounded pitch over a continuous range.

Subsequent improvements to the device include the addition by G. M. Whipple of a gasometer, in order to regulate the incoming air supply.

A version of the device was also produced in which the bottom of the resonator was not displaced by a spiral, but by rack and pinion (see figure); in these, an eccentrically-operated pointer is used to indicate the frequency on the scale.

At first I conceived the problem in purely sensationist terms, sought to determine thresholds experimentally, raised the question of the possible existence of 'transition feelings,' etc.