The coupling of a hearing aid loudspeaker membrane to visco-thermal air layers.

W.R. Kampinga, Ysbrand H. Wijnant, C. Bosschaart, Andries de Boer

Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

4 Citations (Scopus)
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Hearing aids and their components are becoming smaller. This presents new problems for the acoustical components, such as the loudspeaker. A circular membrane of a hearing aid loudspeaker is modeled in this paper. Neglecting air influences, the membrane and its suspension behave as a mass spring system. However, under operating conditions, thin layers of air on both sides of the membrane influence its behavior. Air can enter and leave these layers at certain locations on the circular edge of the layer. Since these air layers are thin, visco-thermal effects may have to be taken into account. Therefore, the air layers are not modeled by the wave equation, but by the low reduced frequency model that takes these visco-thermal effects into account. The equations of this model are solved in a polar coordinate system, using a wave-based method. The other acoustical parts of the hearing aid loudspeaker, and the membrane itself are modeled by simple lumped models. The emphasis in this paper is on the coupling of the viscothermal air layer model to the mechanical model of the membrane. Coupling of the air layer to other acoustical parts by using an impedance as boundary condition for the layer model, is also described. The resulting model is verified by experiments. The model and the measurements match reasonably well, considering the level of approximation with lumped parts.
Original languageUndefined
Title of host publication14th International Congres on Sound Vibration
EditorsB. Randall
Place of PublicationCairns, Australia
Number of pages8
Publication statusPublished - 9 Jul 2007
Event14th International Congress on Sound and Vibration, ICSV 2007 - Cairns, Australia
Duration: 9 Jul 200712 Jul 2007
Conference number: 14


Conference14th International Congress on Sound and Vibration, ICSV 2007
Abbreviated titleICSV


  • IR-58894
  • METIS-245389

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