Optical Microphone Skin-Vibration Sensing for Low-SNR Speech Capture
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Solution Overview
Problem
Conventional audio systems struggle to selectively capture sound from a target acoustic source in noisy environments due to low acoustic signal-to-noise ratio, as they often fail to distinguish between the user's voice and ambient noise.
Innovation Solution
An audio system utilizing an optical microphone with a light source and detector that measures sound by monitoring vibrations on the user's skin or a membrane, employing interferometric or non-interferometric configurations to detect mixed signals, enabling accurate sound measurement even in low SNR conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional microphones are used to capture sound, then the audio system can record ambient sounds, but it fails to distinguish between user voice and noise in low SNR environments
Solution Approach 1:
The patent replaces the conventional acoustic microphone (mechanical sound wave detection) with an optical microphone that uses light to detect skin vibrations. The optical microphone includes a light source that emits light at the skin and a detector that measures the reflected light to detect vibrations caused by sound waves, thereby avoiding the noise interference that plagues conventional acoustic microphones in low SNR environments
Solution Approach 2:
The patent introduces the user's skin as an intermediary medium between the sound source and the detector. Instead of directly detecting sound waves in the air, the system detects vibrations transmitted through the skin, which acts as a mechanical coupling medium that preferentially transmits user-generated sounds (voice, breathing) while filtering out ambient noise
2Adaptability or versatility
If voice activity detectors are used to distinguish user speech, then the system can identify speaking states, but they fail in low acoustic SNR environments where the wearer's voice is masked by noise
Solution Approach 1:
The patent replaces acoustic voice activity detection with optical detection of skin vibrations. The optical microphone continuously monitors skin vibrations caused by user speech, breathing, and other physiological activities, providing reliable voice activity detection regardless of ambient noise levels since it detects mechanical vibrations transmitted through tissue rather than acoustic signals in air
3Quantity of substance
If conventional audio systems are used in noisy environments, then they can capture ambient sound, but they cannot selectively capture sound from a target acoustic source
Solution Approach 1:
The patent uses the user's skin as a selective intermediary that preferentially transmits vibrations from the user's own voice and breathing while attenuating ambient noise. This biological filter provides inherent spatial and source selectivity, allowing the system to capture target sounds (user voice) while rejecting non-target sounds (ambient noise) without requiring complex beamforming or noise cancellation algorithms
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The optical microphone system effectively identifies user speech and ambient sounds with reduced noise interference, eliminating the need for calibration and overcoming limitations of conventional voice activity detectors, particularly in low acoustic SNR environments.
Implementation Method 1
The light source is configured to illuminate skin of the user with the sensing beam. Sounds from the local area (e.g., user's voice, other people, etc.) cause vibrations in the skin of the user.
Implementation Method 2
The detector is an interferometric configuration (e.g., self-mixing, low coherence interferometry, etc.) with the light source such that the detector is configured to detect a mixed signal. The mixed signal corresponds to the reference beam that is mixed with a portion of the sensing beam that is reflected by the skin.
Implementation Method 3
Sounds from the local area (e.g., user's voice, other people, etc.) cause vibrations in the skin of the user. The audio controller is configured to measure the sounds of the local area using the signal.
Data Source
AI summary
An audio system including an optical microphone and an audio controller. The optical microphone includes a light source and a detector. In some embodiments, the light source illuminates skin of a user. Alternatively the optical microphone also includes a membrane, and the light source illuminates a portion of the membrane. Sounds from a local area cause vibrations in the skin (or vibrations in the membrane). The detector may be in an interferometric configuration or a non-interferometric configuration with the light source. The audio controller monitors the vibrations of the skin (or membrane) using signal output from the detector, and measures the sounds using the monitored vibrations.