Microphone Array Gain Equalization for Sensitivity Mismatch
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Solution Overview
Problem
Multi-microphone systems face performance degradation due to manufacturing tolerance-induced microphone sensitivity mismatches, leading to reduced signal enhancement and increased production costs, as existing solutions like tight manufacturing tolerances or production line trimming are impractical and costly.
Innovation Solution
Implementing a method that uses Magnitude Squared Coherence for binary classification to determine signal coherence and enable/disable calibration, coupled with a Kalman Filter-based Signal Mismatch Estimator for real-time sensitivity estimation and gain compensation, allowing for scalable microphone arrays to equalize sound pressure levels across microphones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If tight manufacturing tolerances are specified for microphones, then microphone sensitivity mismatch is reduced, but production costs significantly increase
Solution Approach 1:
The patent changes the operational parameters of the microphone system by introducing real-time sensitivity estimation and gain compensation. Instead of relying on precise manufacturing parameters, the system dynamically adjusts the gain of each microphone channel based on estimated sensitivity mismatches, thereby achieving equalization without tight manufacturing tolerances.
Solution Approach 2:
The system performs self-calibration by automatically estimating its own microphone sensitivity mismatches and applying appropriate gain compensation. The calibration process uses the audio signals already present in the environment, eliminating the need for external calibration equipment or procedures, and enables the system to self-correct for manufacturing variations.
2Manufacturing precision
If production line trimming is performed to match microphone sensitivity, then sensitivity mismatch is reduced, but production costs increase and sensitivity may drift over time
Solution Approach 1:
The patent implements a dynamic calibration solution that continuously estimates and compensates for microphone sensitivity mismatches during runtime. Unlike static production line trimming, this approach adapts to actual operating conditions and can compensate for sensitivity drift over time, providing a flexible and cost-effective alternative to permanent manufacturing adjustments.
Solution Approach 2:
The system performs preliminary sensitivity estimation and gain compensation setup during the calibration phase before normal operation begins. This preliminary calibration establishes the baseline gain adjustments needed for each microphone channel, which are then applied continuously during runtime to maintain equalization despite environmental changes or sensitivity drift.
3Ease of manufacture
If microphone sensitivity mismatch is not compensated, then production costs are reduced, but beamforming performance significantly degrades
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors the audio signals from multiple microphones, estimates the sensitivity mismatches based on the received signals, and adjusts the gain of each channel accordingly. This closed-loop approach ensures that beamforming performance is maintained despite manufacturing variations, as the system actively compensates for mismatches in real-time.
Solution Approach 2:
The patent introduces gain compensation factors as intermediary elements between the raw microphone signals and the beamforming processing. These gain factors act as mediators that equalize the sensitivity differences between microphones, allowing the beamforming algorithm to operate on uniformly scaled signals and achieve optimal performance without requiring precise manufacturing matching.
Data Source
AI summary
The proposed invention implements real-time sensitivity estimation, using a microphone path, and variable gain. When a multi-microphone system is configured to perform in its target use case, and the microphone gain is estimated, and the system output is corrected for performance degradation, sensitivity compensation is performed. A classification system is implemented to enable or disable subsequent gain estimation, and hence power consumption required when enabled or disabled, on a frame-by-frame basis. An acoustic environment is used to trigger a classification system, with electrical power consumption analysis performed to detect audio segments. The approach to the microphone sensitivity mismatch problem is to estimate the mismatch at runtime and provide gain compensation, and provide runtime compensation for the difference in sensitivity to sound pressure level between transducer elements in an array of 2 or more microphones.