Maximum stable gain and fitting range of percutaneously applied bone conduction devices

Area of Science:

• Audiology
• Biomedical Engineering
• Hearing Science

Background:

• Bone conduction devices (BCDs) offer an alternative for hearing loss.
• Understanding the gain limits and fitting ranges of BCDs is crucial for effective use.

Purpose of the Study:

• To measure the maximum stable gain (MSG) and its variability in users of percutaneous power BCDs.
• To establish an MSG-based fitting range for BCDs.
• To assess the available aided dynamic range with BCDs.

Main Methods:

• MSG was measured with the BCD on a participant's head and output on a skull simulator.
• A fitting range was determined using the speech intelligibility index.
• 42 adult BCD users participated in the study.

Main Results:

• MSG averaged 13.3 ± 3.2 dB for device 1 and 16.1 ± 5.9 dB for device 2.
• The fitting range for good speech understanding was 35-40 dB HL, and 45-50 dB HL for moderate-to-sufficient understanding.
• Output was generally not limited by maximum force, except at low frequencies.

Conclusions:

• The maximum usable gain in percutaneous power BCDs is limited by feedback, reducing speech intelligibility.
• BCDs provide sufficient speech intelligibility primarily for mild-to-moderate sensorineural hearing loss.
• The aided dynamic range is adequate for hearing thresholds within the determined fitting range.