An electrostatic audio generator

Design and operating features of a multi-harmonic electrostatic audio frequency generator are described in this paper. The harmonics are generated singly by the rotation of a shielded segmented disk adjacent to a stationary wave pattern plate; the resulting changes in capacitance between disk and plate produce a sinusoidal charging and discharging current through an input resistance of a vacuum tube amplifier. Each harmonic is controlled independently in amplitude and in phase, and provisions are made for combining any 2 or more harmonics to obtain complex wave forms. Although designed specifically for psychological tests, the device should prove useful in any work requiring a flexible audio frequency supply of small capacity.