The Mechanism of Hearing by Electrical Stimulation
S. S. Stevens, R. Clark Jones · The Journal of the Acoustical Society of America · 1939
The harmonic components in the complex tone heard when a sinusoidal electric current is passed through the head were measured by the method of “best beats.” The relative intensity of these components was determined with and without a polarizing d.c. simultaneously applied. With no d.c. the observer hears only the second harmonic of the stimulating frequency, but in the presence of a d.c. he hears the fundamental as well. The quantitative relations between the perceived harmonic components and the polarizing current demonstrate that the response of the ear to electrical stimulation follows a square law. On the assumption that the eardrum is moved by electrostatic pressure whenever there is a difference of potential between the eardrum and the inner surface of the middle ear, it is possible to account for the square-law response, and for certain other aspects of the electrophonic effect. The middle ear appears, therefore, to behave as a condenser receiver. The large amount of distortion which normally prevents an observer from understanding a radio broadcast when the electrical output of a radio receiver is passed directly through his head can be reduced by the application of a polarizing d.c. Under this condition speech and music can be heard with great clarity.