Radio frequency clipping in hearing aids.

Abstract

For those patients with reduced dynamic range of hearing, accomodation of normal dynamic range of speech has always presented a problem. This paper describes a method of overcoming the problem, a method which has the added benefit of offering improved speech discrimination as well as limiting the output from a hearing aid system. The principle employed is the presentation of taped speech material processed through clipping of a radio frequency single side side band suppressed carrier signal, which is filtered to remove the Fourier components and demodulated to obtain the modified speech material. Groups of normally hearing and hearing impaired subjects undergo speech audiometry testing to assess what improvement can be effected by this system. The majority of subjects tested both normal and hearing impaired achieve improved speech discrimination when using the system described. Further once the output was set no increase in the input signal could produce a level in excess of that set by the output control.