Implantable Hearing Devices

Experimental study of an implantable fiber-optic microphone on human cadavers

In this paper, we present the results of an experimental study about a novel fiber optical vibrometer, aimed to be used as a totally implantable fiber-optic microphone for hearing aids. The sensor head, implanted inside the human cadaver middle ear, detects the amplitude of the incus vibrations, which are produced by an external acoustical source. The probe beam of coherent vertical cavity surface emitting laser (VCSEL) radiation is directed to the incus and the phase-modulated reflected beam is captured and demodulated. The problem of interferometric fading was solved using two quasi-quadrature signals, passively produced by the 3 × 3 single-mode fiber-optic coupler, processed by a special embedded algorithm. The implanted optoelectronic module works with very low-power consumption, performs real-time signal processing and outputs an analogue signal proportional to the incus vibration. The amplitude of the incus vibrations at different sound pressure levels (SPL) from 40 to 90 dB and at frequencies from 100 Hz to 10 kHz were measured by the implanted system. The system was evaluated on five cadaver skulls. The measured amplitudes were in the range of 1 pm to 5 nm, depending on the subjected skull and the applied sound pressure.

A New Type of Wireless Transmission Based on Digital Direct Modulation for Use in Partially Implantable Hearing Aids

In this study, we developed a new type of wireless transmission system for use in partially implantable hearing aids. This system was designed for miniaturization and low distortion, and features direct digital modulation. The sigma-delta output, which has a high SNR due to oversampling and noise shaping technology, is used as the data signal and is transmitted using a wireless transmission system to the implant unit through OOK without restoration as an audio signal, thus eliminating the need for additional circuits (i.e., LPF and a reference voltage supply circuit) and improving the ease of implantation and reliability of the circuit. We selected a carrier frequency of 27 MHz after analysis of carrier attenuation by human tissue, and designed the communication coil with reference to both the geometry and required communication distance. Circuit design and simulation for wireless transmission were performed using Multisim 13.0. The system was fabricated based on the circuit design; the size of the device board was 13 mm × 13 mm, the size of the implanted part was 9 mm × 9 mm, the diameter of the transmitting/receiving coil was 26 mm, and the thicknesses of these coils were 0.5 and 0.3 mm, respectively. The difference (error) between the detected and simulation waveforms was about 5%, and was thought to be due to the tolerances of the fabricated communication coil and elements (resistors, capacitors, etc.) used in the circuit configuration of the system. The number of windings was reduced more than 9-fold compared to the communication coil described by Taghavi et al. The measured THD was <1% in the frequency band from 100 Hz to 10 kHz, thus easily meeting the standard specification for hearing aids.

Implantable Hearing Aids: Where are we in 2020?

Beginning in the late 20th century, implantable hearing aids were developed and used as an alternative for individuals who were unable to tolerate conventional hearing aids. Since that time, several devices have been developed, with four currently remaining on the international market (Med-el Vibrant Soundbridge, Envoy Esteem, Ototronix MAXUM, and Cochlear Carina). This review will briefly examine the history of middle ear implant development, describe current available devices, evaluate the benefits and limits of the technology, and consider the future directions of research in the field of implantable hearing aids.

Comparative outcomes of active and passive hearing devices by transcutaneous bone conduction

Conclusion Bonebridge (BB) and Sophono (SP) devices improved hearing; with the BB implant showing a better performance at medium and high frequencies. Furthermore, the BB, as an active implant, showed higher functional gain and increased time of use, when compared to the SP, a passive system. Objectives This study aims to compare surgical and audiological outcomes of SP and BB devices in order to assess and further differentiate the indication criteria. Methods Fourteen patients with conductive and mixed hearing loss were evaluated pre- and post-operatively (BB or SP) (period 2013-2014). Age, gender, surgical history, cause and type of hearing loss, implant use per day, levels of bone and air conduction, and functional gain were recorded. Data was analysed by Wilcoxon singed-rank and Wilcoxon rank-sum tests. Results Fourteen patients (BB; n = 10 and SP; n = 4) with an average age = 25.42 years (CI95 = 12.41-38.43) were evaluated. The gender relation was equal (1:1), with pre-implantation osseous thresholds of 20.42 dB (CI95 = 11.15-29.69), and pre-implantation aerial thresholds of 70.83 dB (CI95 = 62.52-79.14). The SP wearing time was significantly lower than that of the BB (SP = 7-10 h/day, BB = 8-12 h/day; p = 0.0323). The functional gain did not differ significantly between the two devices (BB = 40.00 ± 13.19 dB, SP = 34.06 ± 15.63 dB; p = 0.3434), but a significant improvement from pre- to post-implantation was observed (p < 0.05). BB and SP decreased auditory thresholds at 1 and 2 kHz (< 0.01), respectively. The BB even significantly decreased thresholds at 0.5 kHz (p = 0.0140) and 4 kHz (p < 0.0001). No relevant surgical complications were found.