An electromagnetically actuated microspeaker with fully-integrated wax-bonded Nd-Fe-B micromagnets for hearing aid applications

We present a fully-integrated, electromagnetically actuated microspeaker intended for hearing aid applications. The microspeaker uses the Lorentz force to actuate multi-turn, multi-layer copper coils embedded in a 3-mm-diameter parylene diaphragm. Process-compatible micromachined permanent magnets are employed for size reduction and batch-manufacturability. The permanent magnets are composed of micro-size Nd-Fe-B particles in a wax binder. The microspeaker produces 0.64 mum peak displacement at 1 kHz for a drive current of 88 mA rms (6 Omega coil impedance), corresponding to a 46 mW power consumption.