Modelling measurement microphones using BEM with visco-thermal losses

Vicente Cutanda Henriquez, Peter Møller Juhl

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Abstract

For many decades, models that can explain the behaviour of measurement condenser microphones have been proposed in the literature. These devices have an apparently simple working principle, a charged capacitor whose charge varies when one of its electrodes, the diaphragm, moves as a result of sound waves. However, measurement microphones must be manufactured very carefully due to their sensitivity to small changes of their physical parameters. There are different elements in a microphone, the diaphragm, the gap behind it, a back cavity, a vent for pressure equalization and an external medium. All these subsystems form a strongly coupled device that cannot be modelled properly as a superposition of submodels, but rather as a whole. For this reason, the challenge of microphone modelling is still an ongoing area of research. In this work, a newly developed Boundary Element Method implementation that includes visco-thermal losses is used to model measurement condenser microphones. The models presented are fully coupled and include a FEM model of the diaphragm. The behaviour of the acoustic variables in the gap and the effect of the pressure equalization vent are discussed, as well as the practical difficulty due to the production variability among single units of the same microphone model.
Original languageEnglish
Title of host publicationProceedings of the Baltic-Nordic Acoustics Meeting 2012
Number of pages9
Publication date2012
Publication statusPublished - 2012
Externally publishedYes
EventJoint Baltic-Nordic Acoustics Meeting 2012 - Odense, Denmark
Duration: 18 Jun 201220 Jun 2012

Conference

ConferenceJoint Baltic-Nordic Acoustics Meeting 2012
CountryDenmark
CityOdense
Period18/06/201220/06/2012

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