Implanted Microphone AGC for Body-Sound Distortion Suppression
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Solution Overview
Problem
Implantable hearing instruments face issues with vibration sensitivity, leading to distortion and feedback due to body sounds and the wearer's own voice, as the skin and tissue covering the microphone increase vibration sensitivity, and existing methods to mitigate this affect sound sensitivity and introduce noise.
Innovation Solution
An automatic gain control (AGC) circuit is implemented in the implantable hearing instrument system to selectively adjust the gain of signals based on their magnitude and frequency content, reducing the amplification of unnaturally large vibrations like the wearer's voice while maintaining sensitivity to desired sounds, and mapping the microphone's dynamic range into the signal processor's range to prevent clipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the microphone is positioned to receive acoustic signals through skin and tissue, then sensitivity to airborne sound is improved, but vibration sensitivity increases causing distortion and feedback
Solution Approach 1:
The signal processing is segmented into multiple stages: initial amplification stage, automatic gain control stage, and signal processing stage. The AGC circuit selectively applies different gain levels to different signal components, separating the handling of desired acoustic signals from unwanted vibrations and feedback.
Solution Approach 2:
The system employs dynamic gain adjustment through the AGC circuit that automatically adapts the amplification level based on the detected signal characteristics. The gain is dynamically changed to be higher for desired sounds and lower for vibrations and feedback, making the system response adaptive rather than static.
2Measurement precision
If gain is increased to amplify desired sounds, then sensitivity to acoustic signals is improved, but feedback and distortion from vibrations are also amplified
Solution Approach 1:
Different quality of amplification is applied to different signal components. The AGC circuit provides high gain for desired acoustic signals while providing low gain for vibrations and feedback, creating local quality differences in the signal processing chain based on signal characteristics rather than uniform treatment.
Solution Approach 2:
The system uses feedback mechanisms where the output signal is monitored and fed back to the AGC circuit. This feedback loop enables the AGC to detect vibrations and feedback signals and automatically adjust the gain to suppress these harmful components while maintaining amplification of desired sounds.
3Reliability
If vibration sensitivity is reduced to eliminate feedback, then distortion is reduced, but sensitivity to desired acoustic signals is also reduced
Solution Approach 1:
The gain structure is made dynamic rather than static. The AGC circuit continuously adjusts the gain level based on real-time signal analysis, enabling the system to maintain high sensitivity for desired sounds while dynamically reducing gain when vibrations or feedback are detected, thus achieving both reliability and sensitivity.
Solution Approach 2:
The AGC circuit performs preliminary action by pre-adjusting the gain level based on detected signal characteristics before the signal proceeds to further processing. This preliminary gain adjustment prevents excessive amplification of vibrations and feedback while maintaining proper amplification of desired acoustic signals.
4Reliability
If automatic gain control is implemented to selectively adjust gain, then feedback and distortion are reduced, but system complexity increases
Solution Approach 1:
The AGC circuit performs multiple functions: it amplifies desired acoustic signals, suppresses vibrations, reduces feedback, and protects against saturation. By consolidating these multiple functions into a single circuit block, the patent reduces overall system complexity compared to implementing separate circuits for each function.
Solution Approach 2:
The patent combines the gain control functionality with the existing amplification stage, merging what could be separate circuits into an integrated AGC system. This merging approach reduces the number of discrete components and simplifies the overall system architecture while achieving the desired feedback and distortion reduction.
Data Source
AI summary
A method for use in an implantable hearing instrument, including receiving an output signal from an implanted microphone implanted in a person, identifying a first characteristic of said output signal, based on said first characteristic, amplifying said microphone output signal by at least one of a plurality of gain settings to produce an amplified signal, wherein said plurality of gain setting comprise at least two different gain settings, inputting said amplified signal into a signal processor, processing said amplified signal to generate a transducer drive signal; and using said transducer drive signal to drive implanted auditory stimulation device implanted in a person to stimulate an auditory component.