• Journal of Sensor Science and Technology
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• v.23 no.3
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• pp.178-184
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• 2014

Key components of implantable hearing aids are consist of an acoustic sensor that collect external sound by suppressing the body noise, a signal processor module for compensation algorithm of hearing loss, and a output transducer which has tiny size but have high efficiency, respectively. In the partial implantable hearing aids, technologies of transducer and signal processor are so matured that can be applied not too much difficulty. However, due to the difficulties in implantable acoustic sensor technology, such as minimization of masticatory sound and damage of sensor's membrane from external impact, practical use of fully implantable hearing aids have not successful so far. In this paper, we have proposed a novel implantable acoustic sensor which has trans-tympanic structure, and is verified that the proposed method can be very useful for fully implantable hearing aids by cadaveric experiments.

• Journal of Korea Multimedia Society
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• v.22 no.8
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• pp.923-929
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• 2019

In this paper, biomimetic based physical ear model proposed for measuring the characteristics of a hybrid-acoustic sensor for fully implantable middle-ear hearing aid. The proposed physical ear model consists of the external ear, middle-ear, and cochlea. The physical ear model was implemented based on the anatomical structure and CT images of the human ear. To confirm the characteristics of the ear model, the vibrational characteristics of the stapes was measured after applying sound pressure to the tympanic membrane. The measured results were compared with the vibrational characteristics of the human temporal bone specified by ASTM F2504-05. Through the comparison results, the feasibility of the proposed ear model was confirmed. Then, after attaching the hybrid-acoustic sensor to the ear model, the output characteristics of the ECM and acceleration sensor were measured according to the sound pressure. The measured results were compared with previous studies using human temporal bone, and the usefulness of the proposed physical ear model was verified through the analysis results.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.11 no.2
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• pp.133-141
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• 2017

The hybrid acoustic sensor for implantable hearing aid has the structure in which a sound pressure based acoustic sensor (ECM) and a vibration based acceleration sensor are combined. This sensor combines the low frequency sensitivity of an acoustic sensor with the high frequency sensitivity of an acceleration sensor, allowing the acquisition of a wide range of sound from low to high frequency. In this paper, an acceleration sensor for use in a hybrid acoustic sensor has been proposed. The acceleration sensor captures the vibration of the tympanic membrane generated by the acoustic signal. The size of the proposed acceleration sensor was determined to diameter of 3.2 mm considering the anatomical structure of the tympanic membrane and the standard of ECM. In order to make the hybrid acoustic sensor have high sensitivity and wide bandwidth characteristics, the aim of the resonance frequency of the acceleration sensor is to be generated at about 3.5 kHz. The membrane of the acceleration sensor derives geometric structure through mathematical model and finite element analysis. Based on the analysis results, the membrane was implemented through a chemical etching process. In order to verify the frequency characteristics of the implemented membrane, vibration measurement experiment using external force was performed. The experiment results showed mechanical resonance of the membrane occurred at 3.4 kHz. Therefore, it is considered that the proposed acceleration sensor can be utilized for a hybrid acoustic sensor.

• Journal of Sensor Science and Technology
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• v.19 no.5
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• pp.361-368
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• 2010

ACROSS device, which is composed of an implantable microphone, a signal processor, and a vibrating transducer, is a fullyimplantable middle ear hearing device(F-IMEHD) for the recovery of patients with hearing loss. And since a microphone is implanted under skin and tissue at the temporal bones, the amplitude of the sound wave is attenuated by absorption and scattering. And the vibrating transducer attached to the ossicular chain caused also the different displacement from characteristic of the stapes. For the gain control of auditory signals, most of implantable hearing devices with the digital audio signal processor still apply to fitting rules of conventional hearing aid without regard to the effect of the implanted microphone and the vibrating transducer. So it should be taken into account the effect of the implantable microphone and the vibrating transducer to use the conventional audio fitting rule. The aim of this study was to measure gain characteristics caused by the implanted microphone and the vibrating transducer attached to the ossicle chains for the gain compensation of ACROSS device. Differential floating mass transducers (DFMT) of ACROSS device were clipped on four cadaver temporal bones. And after placing the DFMT on them, displacements of the ossicle chain with the DFMT operated by 1 $mA_{peak}$ current was measured using laser Doppler vibrometer. And the sensitivity of microphones under the sampled pig skin and the skin of 3 rat back were measured by stimulus of pure tones in frequency from 0.1 to 8.9 kHz. And we confirmed that the microphone implanted under skin showed poorer frequency response in the acoustic high-frequency band than it in the low- to mid- frequency band, and the resonant frequency of the stapes vibration was changed by attaching the DFMT on the incus, the displacement of the DFMT driven with 1 $mA_{rms}$ was higher by the amount of about 20 dB than that of cadaver's stapes driven by the sound presssure of 94 dB SPL in resonance frequency range.

• Journal of Sensor Science and Technology
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• v.18 no.4
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• pp.286-293
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• 2009

The implantable middle ear hearing devices(IMEHDs) have been developed to overcome the conventional hearing aid's problem(ringing effect caused by the acoustic feedback, cosmetic problem, etc.). In the IMEHDs, the vibrating transducer is a key component because its vibration enables to hear for hearing impaired people. The vibrating transducer is implanted on ossicular chain by surgical operation. The coupling status between implanted transducer and ossicular chain has an effect on delivering vibrating force from transducer to stapes. Noninvasive method is required to investigate the output characteristics of IMEHDs after implementation. Recently, emitted sound pressure measuring method of tympanic membrane is proposed to investigate the output characteristics of IMEHDs. However, the relationship between displacement of stapes and sound pressure by tympanic membrane was not cleared. In this paper, displacement of stapes and sound pressure by tympanic membrane were measured using the differential floating mass transducer(DFMT) that implanted on the ossicular chain of the human temporal bone and physical ear model. Through the experiments results, the relationship between displacement of stapes and sound pressure by tympanic membrane was investigated.