Implantable Middle Ear Hearing Devices Research Articles

Effect of magnet position in an electromagnetic transducer for the middle ear implant

The paper is devoted to modelling and numerical analysis of the middle ear with an implantable middle ear hearing device. The main focus is put on electromechanical coupling between the biomechanical subsystem of the middle ear and the electrical subsystem of the implant. The electromechanical coupling describes the interaction between the electrical and mechanical systems, and it is defined as a nonlinear dependence between magnet position and coil transducer centre. This is a novel approach, one that generates new resonances, instabilities, subharmonic as well as chaotic stapes vibrations depending on the voltage excitation. Numerical results of the stapes motion stimulated by a floating mass transducer are compared with the results of experiments performed on the human temporal bones. Findings of this study can be used in practice to develop a better design of a floating mass transducer.

Implementation of a fully implantable middle-ear hearing device chip.

BACKGROUND AND OBJECTIVE:Recently, with the increase in the population of hearing impaired people, various types of hearing aids have been rapidly developed. In particular, a fully implantable middle ear hearing device (F-IMEHD) is developed for people with sensorineural hearing loss. The F-IMEHD system comprises an implantable microphone, a transducer, and a signal processor. The signal processor should have a small size and consume less power for implantation in a human body.METHODS:In this study, we designed and fabricated a signal-processing chip using the modified FFT algorithm. This algorithm was developed focusing on eliminating time delay and system complexity in the transform process. The designed signal-processing chip comprises a 4-channel WDRC, a fitting memory, a communication 1control part, and a pulse density modulator. Each channel is separated using a 64-point fast Fourier transform (FFT) method and the gain value is matched using the fitting table in the fitting memory.RESULTS AND CONCLUSION: The chip was designed by Verilog-HDL and the designed HDL codes were verified by Modelsim-PE 10.3 (Mentor graphics, USA). The chip was fabricated using a 0.18 m CMOS process (SMIC, China). Experiments were performed on a cadaver to verify the performance of the fabricated chip.

Binaural hearing restoration with a bilateral fully implantable middle ear implant.

Thefully implantable middle ear implant (C-FI-MEI) is designed for patients with moderate-to-severe sensorineural hearing loss or those with mixed hearing loss. To analyze the audiological post-operative results of subjects bilaterally implanted with C-FI-MEI. Retrospective study: 14 patients with bilateral, moderate-to-severe, sensorineural or mixed hearing loss were treated. This clinical sample included 14 cases bilaterally implanted (13 sequentially, 1 simultaneously). The evaluation at each follow-up after surgery included otologic examination, a structured interview, and different audiological tests composed of pure tone audiometry, speech in quiet and in noise test, and localization task. The mean follow-up was 67.2 ± 33months. There were no significant differences between pre and post-operative pure tone averages. The patients showed no significant differences between pre-operatively aided and C-FI-MEI implant-aided conditions in terms of word recognition score. Speech perception in noise under different loudspeaker arrangements and localization tests demonstrated a binaural advantage in bilaterally implanted patients. The mean daily use time was 17.4 and 16.7h, respectively, for right and left side. The results for the 14 patients, bilaterally implanted with C-FI-MEI, suggest that bilateral implantation of fully implantable middle ear hearing devices is an effective procedure. 4.

The Influence of Piezoelectric Transducer Stimulating Sites on the Performance of Implantable Middle Ear Hearing Devices: A Numerical Analysis.

To overcome the inherent deficiencies of hearing aids, implantable middle ear hearing devices (IMEHDs) have emerged as a new treatment for hearing loss. However, clinical results show that the IMEHD performance varies with its transducer’s stimulating site. To numerically analyze the influence of the piezoelectric transducer’s stimulating sites on its hearing compensation performance, we constructed a human ear finite element model and confirmed its validity. Based on this finite element model, the displacement stimulation, which simulates the piezoelectric transducer’s stimulation, was applied to the umbo, the incus long process, the incus body, the stapes, and the round window membrane, respectively. Then, the stimulating site’s effect of the piezoelectric transducer was analyzed by comparing the corresponding displacements of the basilar membrane. Besides, the stimulating site’s sensitivity to the direction of excitation was also studied. The result of the finite element analysis shows that stimulating the incus body is least efficient for the piezoelectric transducer. Meanwhile, stimulating the round window membrane or the stapes generates a higher basilar membrane displacement than stimulating the eardrum or the incus long process. However, the performance of these two ideal sites’ stimulation is sensitive to the changes in the excitation’s direction. Thus, the round window membrane and the stapes is the ideal stimulating sites for the piezoelectric transducer regarding the driving efficiency. The direction of the excitation should be guaranteed for these ideal sites.

Influence of ossicular chain malformation on the performance of round-window stimulation: A finite element approach.

As a novel application of implantable middle ear hearing device, round-window stimulation is widely used to treat hearing loss with middle ear disease, such as ossicular chain malformation. To evaluate the influence of ossicular chain malformations on the efficiency of the round-window stimulation, a human ear finite element model, which incorporates cochlear asymmetric structure, was constructed. Five groups of comparison with experimental data confirmed the model's validity. Based on this model, we investigated the influence of three categories of ossicular chain malformations, that is, incudostapedial disconnection, incus and malleus fixation, and fixation of the stapes. These malformations' effects were evaluated by comparing the equivalent sound pressures derived from the basilar membrane displacement. Results show that the studied ossicular chain malformations mainly affected the round-window simulation's performance at low frequencies. In contrast to the fixation of the ossicles, which mainly deteriorates round-window simulation's low-frequency performance, incudostapedial disconnection increases this performance, especially in the absence of incus process and stapes superstructure. Among the studied ossicular chain malformations, the stapes fixation has a much more severe impact on the round-window stimulation's efficiency. Thus, the influence of the patients' ossicular chain malformations should be considered in the design of the round-window stimulation's actuator. The low-frequency output of the round-window simulation's actuator should be enhanced, especially for treating the patients with stapes fixation.

ACTIVE MIDDLE EAR VIBRANT SOUNDBRIDGE SOUND IMPLANT.

SUMMARYThe Vibrant Soundbridge represents a new approach to hearing improvement in the form of active implantable middle ear hearing device. Unlike conventional acoustic hearing aids, which increase the volume of sound that goes to the eardrum, the Vibrant Soundbridge bypasses the ear canal and eardrum by directly vibrating the small bones in the middle ear. Because of its design, no portion of the device is placed in the ear canal itself. The Vibrant Soundbridge has been approved by the FDA as a safe and effective treatment option for adults with moderate to severe sensorineural, conductive or mixed hearing losses who desire an alternative to the acoustic hearing aids, for better hearing. The paper presents a review of the active middle ear implant Vibrant Soundbridge, which has been also implanted at the Department of Otorhinolaryngology and Head and Neck Surgery, Sestre milosrdnice University Hospital Center, which is the Referral Center for Cochlear Implantation and Surgery of Hearing Impairment and Deafness of the Ministry of Health, Republic of Croatia.

Concept and Evaluation of a New Piezoelectric Transducer for an Implantable Middle Ear Hearing Device.

Implantable middle ear hearing devices (IMEHDs) have been developed as a new technology to overcome the limitations of conventional hearing aids. The piezoelectric cantilever transducers currently used in the IMEHDs have the advantages of low power consumption and ease of fabrication, but generate less high-frequency output. To address this problem, we proposed and designed a new piezoelectric transducer based on a piezoelectric stack for the IMEHD. This new transducer, attached to the incus body with a coupling rod, stimulates the ossicular chain in response to the expansion-and-contraction of its piezoelectric stack. To test its feasibility for hearing loss compensation, a bench testing of the transducer prototype and a temporal bone experiment were conducted, respectively. Bench testing results showed that the new transducer did have a broad frequency bandwidth. Besides, the transducer was found to have a low total harmonic distortion (<0.75%) in all frequencies, and small release time (1 ms). The temporal bone experiment further proved that the transducer has the capability to produce sufficient vibrations to compensate for severe sensorineural hearing loss, especially at high frequencies. This property benefits the treatment of the most common sloping high-frequency sensorineural hearing loss. To produce a 100 dB SPL equivalent sound pressure at 1 kHz, its power consumption is 0.49 mW, which is low enough for the transducer to be utilized in the IMEHD.

Analysis of the influence of the transducer and its coupling layer on round window stimulation.

In this work, a finite element study is proposed to evaluate the effects of the transducer and its coupling layer on the performance of round window (RW) stimulation. Based on a set of micro-computer tomography images of a healthy adult's right ear and reverse engineering technique, a coupled finite-element model of the human ear and the transducer was constructed and verified. Then, the effect of the cross-section of the transducer, the elastic modulus of the coupling layer, the mass of the transducer, and the preload of the transducer were studied. The increase of the transducer's cross-section area deteriorates the RW stimulation, especially at the lower frequencies. This adverse effect of the cross-section area's increase of the transducer can be reduced by adding a coupling layer between the transducer and the RW. However, the coupling layer's improvement on the RW stimulation is reduced with the increase of its elastic modulus. Moreover, the mass loading of the transducer decreases the RW stimulation's performance mainly at higher frequencies and applying a static preload on the transducer enhances its hearing compensating performance at higher frequencies. The influence of the transducer's mass, the mass of the transducer, the applied static preload and the properties of the coupling layer must be taken into account in the design of the RW stimulation type implantable middle ear hearing device.

The Effect of Simulated Mastoid Obliteration on the Mechanical Output of Electromagnetic Transducers.

The electromagnetic transducers of implantable middle ear hearing devices or direct acoustic cochlear implants (DACIs) are intended for implantation in an air-filled middle ear cavity. When implanted in an obliterated radical mastoid cavity, they would be surrounded by fatty tissue of unknown elastic properties, potentially attenuating the mechanical output. Here, the elastic properties of this tissue were determined experimentally and the vibrational output of commonly used electromagnetic transducers in an obliterated radical mastoid cavity was investigated in vitro using a newly developed method. The Young's moduli of human fatty tissue samples (3-mm diameter), taken fresh from the abdomen or from the radical mastoid cavity during revision surgeries, were determined by indentation tests. Two phantom materials having Young's moduli similar to and higher than (worst case scenario) the tissue were identified. The displacement output of a DACI, a middle ear transducer (MET) and a floating mass transducer (FMT), was measured when embedded in the phantom materials in a model radical cavity and compared with the output of the nonembedded transducers. The here-determined Young's moduli of fresh human abdominal fatty tissue were comparable to the moduli of human breast fat tissue. When embedded in the phantom materials, the displacement output amplitude at 0.1 to 10 kHz of the DACI and MET was attenuated by maximally 5 dB. The attenuation of the output of the FMT was also minor at 0.5 to 10 kHz, but significantly reduced by up to 35 dB at lower frequencies. Using the method developed here, the Young's moduli of small soft tissue samples could be estimated and the effect of obliteration on the mechanical output of electromagnetic transducers was investigated in vitro. Our results demonstrate that the decrease in vibrational output of the DACI and MET in obliterated mastoid cavities is expected to be minor, having no major impact on clinical indication. Although no major attenuation of vibrational output of the FMT was found for frequencies >0.5 kHz, for implantations in patients the attenuation at frequencies <0.5 kHz may have to be taken into account.

Implantable and semi-implantable hearing AIDS: a review of history, indications, and surgery.

Introduction The complaints associated with the use of conventional amplifying hearing aids prompted research at several centers worldwide that ultimately led to the development of implantable devices for aural rehabilitation. Objectives To review the history, indications, and surgical aspects of the implantable middle ear hearing devices. Data Synthesis Implantable hearing aids, such as the Vibrant Soundbridge system (Med-El Corporation, Innsbruck, Austria), the Maxum system (Ototronix LLC, Houston, Texas, United States), the fourth-generation of Carina prosthesis (Otologics LLC, Boulder, Colorado, United States), and the Esteem device (Envoy Medical Corporation - Minnesota, United States), have their own peculiarities on candidacy and surgical procedure. Conclusion Implantable hearing aids, which are currently in the early stages of development, will unquestionably be the major drivers of advancement in otologic practice in the 21st century, improving the quality of life of an increasingly aged population, which will consequently require increased levels of hearing support.

Delayed facial nerve palsy after surgery for the Esteem® fully implantable middle ear hearing device

Conclusion: Delayed facial nerve (FN) impairment was shown to occur after Esteem® surgery, and taste disturbances were found in a limited number of subjects. Thus, when this type of active middle ear implant (AMEI) is to be implanted, these specific complications need to be shared with the candidate. Objectives: To report on FN involvement in Esteem® AMEI surgery. Methods: A total of 23 males and 11 females, who presented with sensorineural hearing loss of varying severity, underwent surgical implantation of the Esteem® AMEI. FN function was assessed according to the House-Brackmann (HB) grading system. A specific question regarding taste impairment was administered to each patient on the first day and 3 months after surgery. Results: None of the patients presented with a FN deficit in the first postoperative days. In three patients (8.8%), FN palsy developed after 7 days (two patients) and 10 days (one patient), and the severities were HB 4 (two cases) and HB 5 (one case). All patients fully recovered (HB 1) after 6–8 weeks. In 10 of the 34 implanted subjects (29.4%), taste disturbances were found on postoperative day 1, and these impairments remained in only 6 (17.6%) patients at the 3-month postoperative follow-up.

Implementation of wireless remote controller with the function of tracking inner coil position for implantable active medical devices

A popular technique for wireless power transfer and data communication between fully implantable active medical devices and base stations is inductive coupling. A weakness of current technology means that the magnetic coupling coefficient is sharply decreased by variations in the distance and misalignment between two coils. This can result in degradation of com- munication and efficiency of power transfer between implants and external devices. In this paper, a method to track the coil position of the implant device using a 3-axis magnetic sensor module in the wireless remote controller has been proposed for efficient power transfer and robust data communication. The magnetic sensor module is implemented for obtaining the magnetic flux vector of the magnet in the middle of the inner coil. Based on the obtained magnetic flux vector, the pseudo-distance vector between the inner coil and the outer coil can be calculated and the position of the inner coil can be tracked. From experiments to evaluate the performance of the implemented remote controller's ability to find the inner coil position, we found that our remote controller could track the position of the inner coil of the implant device with the averaged error range of 3.73 mm and increase to a maximum of about 30% above the minimal power requirement for charging a battery of the mock-up implant device. It is expected that the implemented remote controller can be used for implantable active medical devices such as fully implantable middle ear hearing devices.

The effect of static force on round window stimulation with the direct acoustic cochlea stimulator

The Direct Acoustic Cochlea Stimulator Partial Implant (DACS PI, Phonak Acoustic Implants SA, Switzerland) is intended to stimulate the cochlea by a conventional stapedotomy piston that is crimped onto the DACS PI artificial incus. An alternative approach to the round window (RW) is successfully done with other devices, having the advantage of being also independent of the existence of middle ear structure (e.g. ossicles). Here the possibility of stimulating the RW with the DACS actuator is investigated including the impact of static force on sound transmission to the cochlea.The maximum equivalent sound pressure output with RW stimulation was determined experimentally in fresh human temporal bones. Experiments were performed in analogy to the ASTM standard (F2504.24930-1) method for the output determination of implantable middle ear hearing devices (IMEHDs) in human cadaveric temporal bones (TBs). ASTM compliant temporal bones were stimulated with a prosthesis having a spherical tip (∅0.5 mm) attached to the actuator. The stimulation was performed perpendicular to the round window membrane (RWM) at varying position relative to the RW and the resulting static force on the RW membrane was determined.At each position the displacement output of the DACS PI actuator and the stapes footplate (SFP) vibration in response to actuator stimulation was measured with a Laser Doppler Velocimeter (LDV). By comparison of the achieved output at the stapes footplate in response to sound and transducer stimulation the equivalent sound pressure level at the tympanic membrane at 1Vrms input voltage was calculated assuming that the SFP displacement in both conditions is a measure of perceived loudness, as it is done in the ASTM standard.Ten TB preparations within the acceptance range of the ASTM standard were used for analysis. The actuator driven stapes footplate displacement amplitude as well as the resulting equivalent sound pressure level was highly dependent on the static force applied to the RW. The sound transfer efficiency from the RW to the stapes footplate increased monotonically with increasing static load. At a moderate static force load (approx. 3.9 mN) the obtained average sound equivalent sound pressure level was 102–120 eq. dB SPL @ nominally 1Vrms input for frequencies ≤4 kHz. At higher frequencies (6–10 kHz) the achieved output dropped to ∼90 dB SPL.This output was obtained at loading conditions compatible with the actuator safe operating range, although it was possible to increase the output further by increasing the static force load.Our results demonstrate for a first time that static force applied to the RW is crucial for sound transmission efficiency. Further we could show that RW stimulation with the DACS PI actuator is possible having a maximum output that is sufficient to treat moderate and pronounced sensorineural hearing losses (SNHL).This article is part of a Special Issue entitled “MEMRO 2012”.

A Systematic Review of the Safety and Effectiveness of Fully Implantable Middle Ear Hearing Devices

To examine the safety and effectiveness of fully implantable middle ear devices in the treatment of hearing loss. MEDLINE, EMBASE, The Cochrane Library, Web of Science, CINAHL, PsycINFO, and the Centre for Reviews and Dissemination were searched without date or language limits. Titles and abstracts of 7,700 citations were screened, and 30 articles were selected for full review, of which, 7 articles on the Esteem and 13 on the Carina met the study's eligibility criteria. Information was extracted using a pretested data abstraction form, and study quality was assessed using the Oxford Centre for Evidence-Based Medicine Levels of Evidence. Because of heterogeneity across studies, meta-analysis was not performed, and comparisons were made by structured review. The majority of studies were quasi-experimental, prepost comparisons of aided and unaided conditions. Complication rates with the Esteem were higher than with the Carina, and most commonly included taste disturbance. However, device failure was common with the Carina, predominately related to charging difficulties. For both devices, clinically significant improvements in functional gain, speech reception, and speech recognition over the unaided condition were found. In studies comparing the Esteem or Carina to hearing aids, findings were mixed. Although improvements in functional gain were similar to those for hearing aids, speech recognition and quality of life were greater with the implants. Despite limited evidence, these devices seem to offer a relatively safe and effective treatment option, particularly for patients who are medically unable to wear conventional hearing aids.

Design of wavelet frequency-division based signal processing algorithm for an implantable middle ear hearing device

A signal processing algorithm was designed based on wavelet frequency division for an implantable middle ear hearing device(IMEHD) to make the piezoelectric actuator's vibration simulate normal middle ear transfer function. Firstly, the input digital signals were divided into seventeen bands based on Bark frequency scale using wavelet transform. Then, the assigned band gains were applied corresponding to middle ear transfer function. Finally, the algorithm was implemented and verified the performance through an experiment. The satisfactory agreements between the output of the piezoelectric stack and normal middle ear transfer function indicate that the designed algorithm is feasible. This work is supported by the National Natural Science Foundation of China (Grant No. 11072145 and No. 81170910) and the Science and Technology Commission of Shanghai Municipality Foundation (No. 08JC1404700). We are also thankful to Dr S. K. Yin, Department of Otolaryngology, Shanghai Sixth People's Hospital, China, for the facilities and encouragement given.

Letter to the Editor First bilateral simultaneous implantation with fully implantable middle ear hearing device

The majority of moderate to severe sensorineural hearing loss individuals must rely on amplification of the acoustic signal to improve communication skills. This aim is generally accomplished with conventional air conduction hearing aids [1]. In some cases, hearing aid wearers report difficulties and limited adoption of hearing aids due to ear canal occlusion, pain or irritation of the skin in the ear canal, social stigma, and cosmetic issues [2]. The fully implantable middle ear hearing device is now an alternative solution for those patients. It resides completely underneath the skin behind the ear, with nothing in the external ear canal. The Otologics Carina implant is composed of an electronic capsule, microphone, and electromagnetic transducer. The battery, magnet, digital signal processor, coil, and connector make up the electronic capsule [1, 2]. The sensitive subcutaneous microphone picks up the acoustic signal, which is then translated into a digital signal, amplified according to the wearer’s needs, and converted into the electrical signal. This electrical signal is sent to the electromagnetic transducer, which translates it into a mechanical motion that directly stimulates the ossicles. The tip of the transducer touches the middle ear ossicular chain, round or oval window and in this way bypasses the external ear canal [1-5]. Besides the fully implantable part, three other components are also important for this hearing device: the programming system, the charger, and the remote control. The charging time of the battery in the newest Carina device typically requires 45 min to 1 h, if performed daily. The fully implantable middle ear hearing system Carina is designed to deal with moderate to severe hearing loss in adults with normal middle ears, and no signs or symptoms of retrocochlear, central auditory or functional components. Most recently it has been successfully used in patients with ossicular chain malformations in conductive and mixed hearing loss [6-9]. In this paper the authors present a case report of the first bilateral simultaneous implantation with a fully implantable middle ear hearing device. Candidacy criteria and preoperative and postoperative audiological results are reported, and advantages obtained with these implants are discussed. One patient was included in this retrospective case report. To our best knowledge it is the first reported case of bilateral simultaneous implantation with a fully implantable middle ear hearing device. The surgery took place in the Department of Otolaryngology at the Medical University of Corresponding author: Magdalena Lachowska MD, PhD Department of Otolaryngology Medical University of Warsaw 1a Banacha 02-097 Warsaw, Poland Phone: +48 22 5992521 Fax: +48 22 5992523 E-mail: mlachowska@wum.edu.pl Letter to the Editor

Profound High-Frequency Sensorineural Hearing Loss Treatment With a Totally Implantable Hearing System

This study seeks to assess the efficacy of the Envoy Esteem totally implantable hearing device in treating profound high-frequency sensorineural hearing loss. Five patients with profound high-frequency hearing loss participating in a prospective, multi-center, nonrandomized Food and Drug Administration clinical trial. Implantation with Esteem totally implantable hearing device and comparison to baseline unaided and aided conditions. Speech reception threshold and word recognition scores (WRS) at 50 dB HL presentation level. Preoperative speech reception threshold improved from an unaided 65 dB and aided 48 dB average to 26 dB with the Esteem at 12 months. WRS at 50 dB scores improved from an unaided 10% and aided 23% average to 78% postoperatively. The Esteem totally implantable middle ear hearing device provides appreciable functional gain and improvement in WRS to rehabilitate hearing in patients with a profound high-frequency sensorineural hearing loss.

고효율 전자기형 정원창 구동 트랜스듀서의 설계

Implantable middle ear hearing devices(IMEHDs) have being actively studied to overcome the problems of conventional hearing aids. Vibration transducer, an output devices of IMEHDs, is attached on the ossicular chain and transmits mechanical vibration to cochlea. This approach allows us to hear more clear sound because mechanical vibration is effective to transfer high frequency acoustics, but occurs some problems such as fatigue accumulation to ossicular chian and reduction of vibration displacement caused by mass loading effect. Recently, many studies for the round window stimulation are announced, because it does not cause such problems. It have been studied by older transducers designed for attaching on ossicular chain. In this paper, we proposed a new electromagnetic transducer which consists of two magnets, three coils and a vibration membrane. The magnet assembly, magnet coupled in opposite direction, were placed in the center of three coils, and the optimum length of each coil generating maximum vibrational force was calculated by finite element analysis(FEA). The transducer was implemented as the calculated length of each coil, and measured vibration displacement. From the results, it is verified the vibration displacement can be improved by optimizing the length of coils.

Comparisons of electromagnetic and piezoelectric floating-mass transducers in human cadaveric temporal bones

Electromagnetic floating-mass transducers for implantable middle-ear hearing devices (IMEHDs) afford the advantages of a simple surgical implantation procedure and easy attachment to the ossicles. However, their shortcomings include susceptibility to interference from environmental electromagnetic fields, relatively high current consumption, and a limited ability to output high-frequency vibrations. To address these limitations, a piezoelectric floating-mass transducer (PFMT) has recently been developed. This paper presents the results of a comparative study of these two types of vibration transducer developed for IMEHDs. The differential electromagnetic floating-mass transducer (DFMT) and the PFMT were implanted in two different sets of three cadaveric human temporal bones. The resulting stapes displacements were measured and compared on the basis of the ASTM standard for describing the output characteristics of IMEHDs. The experimental results show that the PFMT can produce significantly higher equivalent sound pressure levels above 3 kHz, due to the flat response of the PFMT, than can the DFMT. Thus, it is expected that the PFMT can be utilized to compensate for high-frequency sensorineural hearing loss.

A Micropower Miniature Piezoelectric Actuator for Implantable Middle Ear Hearing Device

This paper describes the design and development of a small actuator using a miniature piezoelectric stack and a flextensional mechanical amplification structure for an implantable middle ear hearing device (IMEHD). A finite-element method was used in the actuator design. Actuator vibration displacement was measured using a laser vibrometer. Preliminary evaluation of the actuator for an IMEHD was conducted using a temporal bone model. Initial results from one temporal bone study indicated that the actuator was small enough to be implanted within the middle ear cavity, and sufficient stapes displacement can be generated for patients with mild to moderate hearing losses, especially at higher frequency range, by the actuator suspended onto the stapes. There was an insignificant mass-loading effect on normal sound transmission (<3 dB) when the actuator was attached to the stapes and switched off. Improved vibration performance is predicted by more firm attachment. The actuator power consumption and its generated equivalent sound pressure level are also discussed. In conclusion, the actuator has advantages of small size, lightweight, and micropower consumption for potential use as IMHEDs.