Anatomical vibrations that implantable microphones must overcome

Area of Science:

• Biomedical Engineering
• Acoustics
• Audiology

Background:

• Totally implantable hearing devices are sought after by individuals with hearing loss.
• Understanding tissue vibration is crucial for designing effective implantable microphones that can isolate desired sounds from noise.
• Anatomical and transducer-generated vibrations must be quantified to optimize device performance.

Purpose of the Study:

• To measure tissue vibration amplitudes relevant to implantable microphone design.
• To characterize anatomical noise sources and their impact on implanted transducers.
• To evaluate the suitability of human cadavers for simulating cranial vibration studies.

Main Methods:

• Laser Doppler vibrometry and accelerometry were used to measure tissue vibrations.
• Vibrations were recorded in normal subjects during vocalization and biological sound production.
• Transducer vibrations were measured on a semi-implantable device wearer and in human cadavers.

Main Results:

• Anatomical noise is significantly higher in soft tissue (<1,000 Hz) than on the cranium.
• Transducer vibrations are greater on the cranium than in soft tissue.
• Chewing vibrations on the mastoid are more intense than vocalization vibrations.

Conclusions:

• Vocalization in soft tissue and chewing on the mastoid represent the primary vibration challenges for implantable microphones.
• Human cadavers provide a valid model for studying cranial transducer vibrations.
• Microphone placement near the pinna on the cranium shows minimal location-dependent vibration differences.