Characterization of the Dominant Structural Vibration of Hearing Aid Receivers

The overall aim of this research is to analyze and characterize the mechanical vibration of hearing aid receivers, a key electro-acoustic component of hearing aids. The receiver is a high efficiency miniature sound source which utilizes a balanced armature electromagnetic motor. A standard side effect for most balance armature receivers is structural vibration. This receiver-borne structural vibration can travel through the hearing aid package to the microphones, resulting in undesirable oscillations, just like acoustic feedback. To better understand and control this important source of feedback in hearing aids, a simple dynamic model has been developed to describe the system. The model consists of two rigid bodies connected by a torsional spring and damper. A method was developed to estimate the parameters for the dynamic model using experimental data. The data were collected using translational velocity measurements using a scanning laser vibrometer of a Knowles ED-series receiver on a complaint foundation. The analytical dynamic model was validated with finite element analysis using COMSOL and the multibody dynamics module.