In situ Probe Microphone Measurement for Testing the Direct Acoustical Cochlear Stimulator

Area of Science:

• Biomedical Engineering
• Otolaryngology
• Medical Acoustics

Background:

• The direct acoustic cochlear stimulator (DACS) is an active hearing implant utilizing an electromagnetic actuator.
• The DACS actuator's diaphragm movement generates sound in the mastoid cavity, in addition to mechanical stimulation.

Purpose of the Study:

• To investigate the feasibility of using DACS sound emission for intra-operative and post-operative functional testing.
• To evaluate acoustical measurements for monitoring DACS actuator performance.

Main Methods:

• Measured sound emission in the external auditory canal (P_EAC) and actuator rod velocity (V_act) in five implanted ears.
• Assessed the impact of microphone and loudspeaker positioning on P_EAC.
• Simulated implant malfunction to evaluate detection capabilities.

Main Results:

• DACS sound emission was detectable between 0.5 and 5 kHz (SNR >10 dB).
• Implant misplacement or malfunction was identifiable by the absence or shift in the actuator's resonance frequency.
• P_EAC showed minimal variation (<6 dB) with changes in microphone and loudspeaker positions.

Conclusions:

• Acoustical measurements are feasible for in situ testing of DACS implants.
• This technique supports post-operative monitoring of DACS actuator function.
• Sound emission analysis offers a non-invasive method for assessing hearing implant performance.