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Next-Generation Hearing

World Listening Day provides an opportunity to explore the innovation of new-generation hearing devices. In particular, this article focuses on bone conduction hearing devices that offer a solution for conductive hearing loss caused by issues in the outer or middle ear. These devices transmit sound vibrations through the skull bone, bypassing the damaged areas. A recent research project aimed to evaluate commercially available drivers capable of amplifying processed signals for the transducer in bone conduction devices. The project also explored modifications for power efficiency, assessed MRI compatibility, and examined battery alternatives. This article provides an overview of the project's objectives, methods, and key findings.

Next-Generation Hearing: Advancements in Bone Conduction Hearing Devices - Evaluating Drivers and Power Efficiency

The purpose of this project was to evaluate and investigate if any commercial driver could amplify the processed signal enough in order to drive the transducer with as low power consumption as possible. In this project a couple of commercial drivers were tested and eventually one driver fulfilled the requirements since the driver provides a high output force and is able to drive the transducer sufficiently.
Gerle, A., & Johansson, E. (2023). Implantable electronics for next-generation hearing implant.

Understanding Bone Conduction Hearing Devices

Bone conduction hearing devices operate by transmitting sound vibrations through the skull bone. They consist of several components, including the AM modulator/demodulator, driver/amplifier, and transducer. The AM modulator/demodulator processes the input sound signal, while the driver/amplifier amplifies the processed signal and drives the transducer. These devices offer an alternative solution for individuals with conductive hearing loss, as they directly stimulate the inner ear.

Challenges of MRI Compatibility

One challenge faced in developing bone conduction hearing devices is ensuring MRI compatibility. Magnetic materials can interfere with the magnetic field used in MRI scans. Therefore, it is crucial to limit the use of such materials in the device's construction. The research project outlined in the paper aimed to assess the MRI compatibility of the drivers used in bone conduction devices.

Exploring Power Efficiency

The project also aimed to explore modifications for improving power efficiency in bone conduction devices. While the paper does not extensively discuss modifications to components, it does address the removal of the driver's inductor to enhance MRI compatibility. However, this modification resulted in increased power consumption, leading to further investigations into alternative solutions.

Evaluating Commercial Drivers

The research project involved testing and evaluating various commercially available drivers. Four drivers provided by Oticon Medical were tested, and one driver met the requirements for further testing. The initial evaluation focused on amplification and power consumption. The third driver exhibited promising results in terms of amplification and power consumption, making it the preferred choice for further testing.

The first step was to design it online and test if it worked in simulation before constructing it in real life. The idea is to have the positive cycle of the AM signals go into the voltage multiplier and the negative side of the signal go into the AM demodulator.
Gerle, A., & Johansson, E. (2023). Implantable electronics for next-generation hearing implant.

Measurement Results and Further Testing

Further testing was conducted on the selected driver using sinusoidal waves at various frequencies. The power consumption of the driver, power output of the transducer, and force output over a skull simulator were measured. The results demonstrated that the driver's power consumption remained within the desired range, and the force output showed a peak at approximately 1kHz. The power delivered to the transducer exceeded the driver's power consumption, indicating efficient energy transfer.

The research project also involved designing an AM demodulator, which was tested using simulations and constructed in real life. The simulation and measurement results aligned, confirming the accurate performance of the AM demodulator.

Addressing Inductor Challenges

The project encountered challenges with the driver's inductor, which needed to be replaced with a non-magnetic alternative for MRI compatibility. Various non-magnetic inductors were tested, including air core, silica, and plasma inductors. While an air gap inductor showed promising results, it led to increased power consumption. Ultimately, it was discovered that the driver could operate without an inductor without significant impact on performance.

Complete System Testing

The complete bone conduction system was tested, comparing the performance with and without an inductor. The results indicated minimal differences in output force and power consumption, suggesting that the inductor had negligible effects on the system's functionality. Additionally, tests were conducted on force levels at different sound pressure levels, and the total harmonic distortion (THD) of the system was measured.

Conclusion and Future Directions

In conclusion, the research project successfully identified a commercially available driver suitable for bone conduction devices, meeting requirements for amplification, power consumption, and THD. The project partially addressed the objectives, including driver evaluation, MRI compatibility assessment, and power efficiency exploration. Future work should focus on optimizing power efficiency, conducting MRI scan tests, and further investigating potential modifications for improved performance. These advancements will contribute to the ongoing innovation of new-generation bone conduction hearing devices, enhancing the lives of individuals with conductive hearing loss.

World Listening Day serves as a reminder of the importance of innovations in hearing technology, and this research project contributes to the continuous improvement of bone conduction devices. By evaluating drivers, optimizing power efficiency, ensuring MRI compatibility, and exploring battery alternatives, the project paves the way for more effective and accessible hearing solutions.