A tri-coil bellows-type round window transducer with improved frequency characteristics for middle-ear implants

Area of Science:

• Biomedical Engineering
• Otolaryngology
• Medical Devices

Background:

• Floating mass transducers (FMTs) are used to drive the round window (RW) but exhibit low output below 1 kHz.
• Existing FMT methods are relatively easy to implant in the RW niche.
• There is a need for improved transducers with better low-frequency performance for RW stimulation.

Purpose of the Study:

• To propose and design a new tri-coil bellows-type transducer (TCBT) for enhanced round window (RW) stimulation.
• To evaluate the frequency characteristics and performance of the TCBT compared to existing transducers.
• To assess the ease of implantation and efficacy of the TCBT in a biological model.

Main Methods:

• Mechanical and electrical simulations were performed to design the TCBT's frequency characteristics.
• A comparative analysis was conducted between the proposed TCBT and a floating mass type transducer (FMT).
• The TCBT was implanted in the RW niche of temporal bones, and stapes velocity was measured using laser Doppler vibrometry.

Main Results:

• The TCBT features a fixed housing, a vibrating bellows, and a three-pole magnet within field coils, isolating vibration to the bellows.
• Experimental results show the TCBT achieves equivalent pressure outputs of 100 dB SPL below 1 kHz, 111 dB SPL between 1-3 kHz, and 129 dB SPL above 3 kHz.
• The TCBT demonstrates superior performance compared to the FMT, particularly at lower frequencies.

Conclusions:

• The novel tri-coil bellows-type transducer (TCBT) offers excellent low-frequency output for round window (RW) stimulation.
• The TCBT design is easy to implant and provides better performance than the floating mass transducer (FMT).
• This transducer represents a significant advancement in auditory stimulation technology.