Improved acoustic coupling between the hearing aid and the telephone
H. Arndt, J. J. Wojick · The Journal of the Acoustical Society of America · 1977
Technological evolution in telephone-receiver design has necessitated a closer examination of the ways in which hard of hearing telephone users employ their hearing aids. All hearing aids pick up acoustic signals with a microphone. In addition, some hearing aids have a magnetic pickup coil (telecoil) for sensing magnetic fields. Magnetic leakage from telephone receivers is usually a by-product of a particular design and does not exist for some designs and for receivers which incorporate nonmagnetic technologies. In order to maintain a uniform level of access to the telephone for hearing-aid users. one needs to make acoustic coupling the accepted and preferred method of interfacing between a hearing aid and the telephone. Three approaches for acoustic coupling between hearing aids and the telephone are investigated (1) conducting acoustic energy from the receiver-ear cavity to the hearing-aid microphone with an acoustic tube, (2) placing a microphone in the ear cavity (ear mold) and connecting it electrically into the hearing-aid amplification circuitry, and (3) placing the microphone behind the ear in the body of the hearing aid and coupling to it through the pinna. The results are discussed in this paper.