doi: 10.3850/978-981-11-0749-8_732
Investigation of Bandgap Microstructure for Miniaturized Acoustic-Mechanical Devices: Application to BTE Hearing Aid Design
Junghwan Kook and Jakob S. Jensen
Department of Electrical Engineering, Technical University of Denmark, Kgs. Lyngby, 2800, Denmark
Abstract
The bandgap phenomenon, i.e., the existence of frequency ranges for which waves cannot propagate, is exploited for their potential use in acoustic mechanical devices such as hearing aids. In this respect, we study the potential for using a bandgap microstructure for reducing the interaction and resulting vibration problems in coupled acoustic mechanical micro systems. Finite element analysis with acoustic structure interaction (ASI) is used to study the dynamic and acoustic response of representative non planar plate unit cell and the Bloch-Floquet theory is used to apply the results to an infinite material. We conduct several numerical experiments to gain physical insight into how coupled bandgaps in the acoustic and mechanical domains can be created and located at desired frequency ranges and with specific geometrical dimensions. In addition, the bandgap properties are analyzed in view of the possibility for the control of mechanical waves in the presence of strong ASI. The coupled bandgap phenomenon is investigated based on the result of a vibro-acoustic analysis for an acoustic cavity with a corresponding periodic structure made from the non-planar unit cell. Particular attention is given to the effect on both vibrational/acoustic properties of the finite structure.
Keywords: Bandgap, Acoustic structure interaction, Microstructure, Hearing Aids.
