Wax Guard Acoustics: Transfer Matrix Computation

Application ID: 77691

In this tutorial, the acoustic properties of a wax guard are analyzed. A wax guard is a small perforated mesh used to protect the receiver (the miniature loudspeaker in a hearing aid) used for receiver-in-the-ear (RITE) or receiver-in-canal (RIC) hearing aids. Because of the very small dimensions of the structure the thermal and viscous boundary layer losses need to be included in detail, and therefore the Thermoviscous Acoustics, Frequency Domain interface is used.

In the first step, the transfer matrix (or two-port) of the wax guard is computed using the Port Sweep functionality and the Port boundary conditions. The wax guard geometry is imported from a CAD file and prepared for simulation.

In the second step, the response of the wax guard sub-system, when placed in a typical measurement setup, is computed and compared to actual measurements. This is done using the lumped transfer matrix approach. The computed wax guard transfer matrix is used together with other transfer matrix components for a receiver (miniature loudspeaker), a narrow pipe, and a coupler volume.

This model example illustrates applications of this type that would nominally be built using the following products: