Comparative study of efficiency and characteristics of FMT and DRT installed in human cadavers for round-window stimulation

Abstract

Acoustic hearing aids generate amplified sound in the ear canal, and they are the standard of care for patients with mild to moderate sensorineural hearing loss. However, because of their limited frequency bandwidth, gain, and feedback, there is substantial room for improvement. Active middle ear implants, which directly vibrate the middle ear and cochlea, are an alternative approach to conventional acoustic hearing aids. They provide an opportunity to improve sound quality and speech understanding with amplification rehabilitation. For floating-mass type and direct-rod type (DRT) middle ear transducers, a differential floating-mass transducer (DFMT) and a tri-coil bellows transducer (TCBT), respectively, were fabricated to measure the output characteristics in four human temporal bones. Both were fabricated to have similar output forces per unit input and were placed in four human temporal bones to measure their output performances. The TCBT resulted in higher output than did the DFMT throughout the audible frequency range, and the output was more prominent at lower frequency ranges. In this study, we showed that DRT was a more effective method for round window stimulation. Because of its frequency characteristics and vibration efficiency, this implantation method can be utilized as a driving solution for middle ear implants.

Acoustic bellows type round window transducer for middle-ear implants

“…The length of the tube was 70 mm, similar to the lead wire length of Vibrant Soundbridge™, a commercial product of RW-MEIs. Considering the RW niche size, the bellows (Servometer Inc., USA) coated with pure gold was custom-made to have an outer diameter of 1.75 mm, an inner diameter of 1.21 mm, a height of 0.83 mm, a thickness of 7.6 µm, and three corrugations 32 . To increase ease of implantation, the size of the ABRT can be further reduced by using only one corrugation.…”