Authors: Yinxin Kou¹, Zhaohai Liu¹, Houguang Liu¹
¹China University of Mining and Technology
Background: Traditional hearing aids often struggle with limited high-frequency gain, while active middle ear implants (AMEIs) require invasive surgery, which presents challenges for patients with sensorineural hearing loss. To address these limitations, a novel direct-drive hearing device actuator (DHDA) was designed, fabricated, and tested. The DHDA represents a new type of auditory prosthetics that combines the placement of completely-in-the-canal (CIC) hearing aid with the avoidance of air conducted sound of AMEIs into a single device.
Methods: The actuator’s front end directly mechanically stimulates the eardrum to compensate for hearing loss. Its components include a base, a compound two-stage (CTS) displacement amplifier, a piezoelectric stack, a shell, a coupling rod, an elastic silicone sleeve, and a coupling layer. In order to analyze the influence of the structural parameters of the CTS displacement amplifier on the displacement amplification ratio, its analytical model was established and its displacement amplification ratio was optimized using a multi-objective genetic algorithm. Then, with the aim of optimizing the frequency characteristics of the actuator, a coupled finite-element model encompassing both the actuator and the human ear was established. Consequently, the optimal structural parameters of the actuator were determined through finite-element analysis. Finally, a prosthetic actuator was manufactured using the optimized parameters, and an experiment was conducted to assess its performance in human cadaveric temporal bones.
Results: Experimental results showed that the measured average displacement amplification ratio of the CTS displacement amplifier at the low-frequency was 11.1. Although it was slightly lower than the finite element analysis prediction (14.6), it still met the design requirements by effectively amplifying the output displacement of the piezoelectric stack. Additionally, the DHDA provides significant advantages in low-frequency compensation. It achieves a wide operating frequency range (0.05–16 kHz) with low total harmonic distortion (THD < 0.12%), indicating superior sound fidelity and efficiency in hearing restoration.
Conclusion: The proposed DHDA presents a promising alternative for treating sensorineural hearing loss by combining the benefits of CIC hearing aids and AMEIs. The key advantage of the proposed DHDA is its enhanced low-frequency compensation performance. Additionally, it offers the advantages of non-invasive installation, a wide operating frequency range, and low harmonic distortion. However, when compared to traditional hearing aids, the convenience of wearing eardrum stimulation type actuators is compromised, typically necessitating precise positioning by an Ear, Nose, and Throat (ENT) specialist. Therefore, the DHDA is a promising candidate for the clinical treatment of sensorineural hearing loss, offering a novel solution in hearing loss therapy.
Disclosure: This work was supported by the GN Foundation.
