Results are presented of an analysis and characterization of the mechanical vibration of hearing aid receivers, a key electroacoustic component of hearing aids. The function of a receiver in a hearing aid is to provide an amplified sound signal into the ear canal. Unfortunately, as the receiver produces sound, it also undergoes vibration which can be transmitted through the hearing aid package to the microphones, resulting in undesirable feedback oscillations. To better understand and control this important source of feedback in hearing aids, a rigid body model is proposed to describe the essential dynamic features of the system. The receiver is represented by two hinged rigid bodies, under an equal and opposite dynamic moment load, and connected to each other by a torsional spring and damper. A method is presented to estimate the parameters for the proposed model using experimental data. The data were collected from translational velocity measurements using a scanning laser vibrometer of a Knowles ED-series receiver supported on a complaint foundation. Excellent agreement is shown between results obtained using the analytical model and the measured translation and rotation of an independent receiver. It is concluded that a dynamic model of the receiver must account for both rotation and translation of the structure in order to properly describe its motion due to an input current.

Balanced armature (BA) receivers can be used as tweeters in earphones to increase their treble and ultra sound bandwidth. Key factors that influence the 9–20 kHz response of earphones when implementing BA tweeters are shown through experimental validation and comparison to newly-developed SPICE lumped parameter models (LPM). While the BA location and acoustic passage inside the earphone are important factors, the study focuses on how changes to the design of the earphone’s nozzle and the choice of ear-tips affect the 9–20 kHz frequency response. Improvements to existing SPICE LPM elements are provided, based on finite element analysis of the acoustic passageway that is formed between the compressed eartip and ear-simulator couplers. The model is compared to measurements from various nozzle and eartip configurations, validating its effectiveness to capture the earphone’s high frequency response due to changes to the earphone’s nozzle and eartip geometry.

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.

The overall aim of this research is to develop practical vibroacoustic models 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. The receiver models are used to help hearing aid designers refine vibration isolation mounts and package components to reduce both acoustic and receiver-borne structural feedback. The model consists of a simplified electro acoustic circuit-equivalent that can easily be coupled to multi-physics finite element analyses. The model has been validated against standard hearing industry measurements and proved to be effective on predicting transmissibility forces across various speaker attachments.