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Optimizing the electromagnetic behavior of hearing aids
In hearing aids with integrated transducers, the magnetic field penetrating the telecoil should not be influenced by internal fields.

Measuring and optimizing the influence of electromagnetic fields in a hearing aid

Branch : Consumer goods/durable goods, Health, Medical technologySpecialist field: Structural mechanics, Electromagnetics

Bernafon, a global hearing healthcare company, helps people to hear and communicate better. Hearing devices with integrated transducers provide increased hearing comfort in public places such as theaters. However, the hearing devices must not be affected by internal electromagnetic fields to achieve this.

Summary

Task

The hearing aid itself typically also emits electromagnetic fields. The aim of the simulations was to investigate the influence of both the shape of the battery springs and the paths of the circuit board on the output signal of the telecoil that detects the external electromagnetic field.

Solution

The induced voltage is determined with the eddy current solver in Ansys Maxwell. The simulation showed that the deformation of the springs, caused by inserting a battery into the device, significantly changes the magnetic field that penetrates the telecoil. With Ansys Mechanical and Ansys Maxwell the behavior could be mapped exactly.

Customer benefits

The simulations of the telecoil, the battery springs and the printed circuit board allow the minimization of the interactions without conducting time and resource intensive experiments. Valuable insights into the electromagnetic coupling mechanisms of the device facilitate a targeted further development of the entire system.

Project Details

Task

Hearing aids with integrated transducers enable increased hearing comfort for the hearing impaired in public places such as theatres and churches. An electromagnetic field is generated with a loop in the ground (hearing loop), which can be detected by a so-called telephone coil (telecoil) in the hearing aid. The hearing aid itself typically also emits electromagnetic fields. These superimposed fields pose a challenge with regard to an electromagnetically robust integration of the telecoil into the device.

For the electromagnetic observations performed, the focus is on the simulation of the telecoil. The aim of the study was - besides the validation of the model - to investigate the influence of both the shape of the battery springs and the paths on  the PCB on the output signal of the telecoil.


Customer Benefit

The project demonstrates that Ansys Maxwell together with Ansys Mechanical is a suitable tool for the simulation of electromagnetic fields in hearing aids and the stationary currents induced therein. This is also proven by the high agreement between measurements and simulations over a wide frequency range.

Furthermore, the telecoil can also be used as a spatial sensor for local field strengths. The simulations of the telecoil, the battery springs and the circuit board allow designers to minimize the interactions between the individual components without the need for time- and resource-intensive experiments. In addition, valuable insights into the electromagnetic coupling mechanisms of the device are gained, thus facilitating a targeted further development of the entire system.


Solution

The induced voltage is determined with the eddy current solver in Ansys Maxwell. Capacitive effects are mapped via a connected external network. Since the battery springs geometrically represent a large coil, they influence the electromagnetic field, which significantly affects what the telecoil detects  and thus also the induced voltage.

The simulation showed that the deformation of the springs caused by inserting a battery into the device significantly changes the magnetic field that penetrates the telecoil. To investigate the interaction of the battery spring as a coil and the telecoil, it was therefore necessary to calculate the mechanical deformations in advance using Ansys Mechanical and to pass on the deformed geometry to Ansys Maxwell. This made it possible to reproduce the behavior exactly.


Head of Communication

Products applied in the project