13 February 2023
Following up on the models presented in the March issue of audioXpress distributed Friday 10 February where two new Balanced Armature Receiver (BAR) lumped models were presented (see also previous blog post), I now present a generic hearing aid in a finite element setting that is fully coupled with a lumped Single BAR. I have not seen this done anywhere before, so it could be of interest to the transducer and hearing aid industry.
An extremely generic hearing aid has two microphone inlets and a rigid body BAR attached via a stiff suspension. The BAR plays into a rigid coupler via a flexible tube.
The lumped model for the Single BAR has been modified so that relevant lumped components have been replaced with couplings to the finite element parts seen above. The coupling is two-way, so that changing anything in the lumped domain will affect the FEM variables, and vice versa. As the membrane moves up in the lumped model, the reaction force is moving the FEM parts, and this loads back onto the lumped circuit. The same thing goes for the pressure, as changes in the acoustic FEM environment will affect all variables in the lumped circuit. The overall behavior is animated below.
The input for the model is an electrical input for the lumped circuit, and ultimately electrical outputs can be found for the microphones for given pressure and velocity sensitivities, since both the pressure and the velocity can be found at the microphone surfaces. These variables will of course change when changing either parameters in the lumped circuit or in the FEM setup due to the full coupling.
This added computational load from connecting the lumped model to the hearing aid FEM model will be very little since the vast majority of the DOFs are in the HA model, and yet it will give new insight to the effects of changing the receiver parameters and/or the overall geometry of the hearing aid, so that for example stability of the hearing aid can be evaluated more systematically.
If anybody wants more details on these new models, feel free to reach out at info@acculution.com. For Danish companies, I can potentially pop by and explain the models, just shoot me a mail.
For those interested in learning how to do lumped modelling or other types of modelling and simulation, check out my new Services Portfolio document (https://www.acculution.com/_files/ugd/a0aa2c_d507fda717ad473689a6dfbb0fdedf58.pdf) where training is one of the options for companies.