Performance evaluation of a novel piezoelectric subcutaneous bone conduction device

Publication date: Available online 6 October 2018

Source: Hearing Research

Author(s): Ivo Dobrev, Jae Hoon Sim, Flurin Pfiffner, Alexander M. Huber, Christof Röösli

Abstract

Objectives

Evaluation of the transfer function efficiency of a newly-developed piezo-electric actuator for active subcutaneous bone conduction hearing aid.

Methods

The experiments were conducted on four Thiel embalmed whole head cadaver specimens. A novel actuator based on piezo-electric transduction (PZTA), part of a subcutaneous bone conduction hearing aid device, was sequentially implanted on three locations: 1) Immediately posterior to pinna; 2) 50-60mm posterior to pinna, approximately the same distance as between the BAHA (bone anchored hearing aid) location and the ear canal, but the same horizontal level as location 1; 3) the traditional BAHA location. Using a single point 3-dimensional laser Doppler vibrometer (LDV) system, three types of motion measurements were performed at the cochlear promontory for each stimulation location: 1) ipsilateral side, 2) contralateral side, 3) measurements 1 and 2 were repeated after mastoidectomy on the ipsilateral side.

Results

On average, stimulation at locations 1 and 2 show a trend for higher promontory motion relative to location 3 (BAHA location) above 1 kHz. Stimulation at location 1 had an average improvement of 1 to 6 dB at 2-4 kHz, and 1 to 18 dB at 6-8kHz. The spatial composition of the motion showed significant contributions from both in-plane and out-of-plane (along ear canal) motion components, with in-plane components being dominant at mid and high frequencies for locations 2 and 3. Stimulation at locations 1 and 3 produced similar transcranial attenuation at mid frequencies (0.6-4kHz), with a potential trend of higher attenuation (seen in 3 or the 4 samples) for location 1 at higher frequencies (>4kHz). The mastoidectomy affected negatively mostly the high frequencies (6-8 kHz) for stimulation at location 1, with no significant change for location 3.

Conclusion

The sound transfer function efficacy of a novel subcutaneous bone conduction device has been quantified, and the influence of stimulation location and mastoidectomy have been analyzed based on promontory motion in Thiel-preserved cadaver heads.

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