Advanced Subminiature Loudspeaker/Earphone Driver

Communication and ear protection in an extremely noisy environment has been aided by the development of noise reduction headsets that employ active feedback between a loudspeaker and microphone, both located within the headset. But externally worn muffs can be dislodged, imperfectly worn, and subject to sound leakage. In addition, their passive noise reduction is limited, particularly at lower frequencies. The development of in-the-ear hearing aids using small electrodynamic receivers and electret microphones has raised the opportunity to incorporate such elements in an in-the-ear active noise reduction communications unit. The principal challenge in doing so is the output capabilities of the receiver. The noise levels at the eardrum with an insert in place may still reach damaging proportions. The receiver must be able to generate pressures of similar magnitude in order to cancel the intruding noise. The purpose of the work described here is to develop a systems model for the ANR earplug and employ that model to evaluate a variety of driver configurations that employ both electrostatic and electromagnetic transduction as a basis for fabrication and testing of candidate drivers in Phase II.