Abstract
Electromagnetic balanced armature receivers [Hunt, Electroacoustics, Chap. 7] are used exclusively to generate acoustic output in hearing aids. These transducers are much more efficient than electrodynamic transducers and are capable of delivering upward of 140 dB of sound pressure to person. In an effort to maximize system gain in a hearing aid, vibroacoustical feedback paths originating from the receiver are modeled using finite elements. Given an electrical excitation, the electromagnetic-mechanical force on the armature is solved as a function of frequency. The force on this armature vibrates an internal diaphragm, which generates acoustic output while vibrating the entire hearing aid. Assuming that there are no acoustical leaks in the design, vibroacoustical coupling limits the usable gain of the aid. Using commercially available software, the fluid is modeled with full Navier–Stokes elements and is coupled to all structural boundaries. The armature is “kicked” with the aforementioned force, and spectral analysis is used to study mechanical transmissibility within and vibroacoustic reradiation around the hearing aid.
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