Microphone Array Beamforming Sensitivity Mismatch Compensation
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Solution Overview
Problem
Microphone array beamformers often increase internal or spatially uncorrelated noise when maximizing gain, which degrades speech communication effectiveness, particularly in applications where microphones are close to each other.
Innovation Solution
The implementation of frequency-dependent microphone gain control, accounting for sensitivity mismatches between microphones in the array, using modified MVDR beamformer coefficients that adjust for microphone sensitivity mismatches to minimize white noise gain while maintaining high array gain, particularly by calculating a modified diffuse noise coherence matrix and deriving new beamforming coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If beamforming gain is maximized to improve speech signal strength, then array gain is improved, but spatially uncorrelated noise (self-noise) is amplified
Solution Approach 1:
The patent applies parameter changes by modifying the beamforming coefficients to account for microphone sensitivity mismatches. Specifically, it introduces a sensitivity mismatch compensation factor that adjusts the weighting of individual microphone signals based on their relative sensitivities. This parameter adjustment allows the system to maintain high array gain while reducing the amplification of spatially uncorrelated noise, as the compensated coefficients optimize the signal combination to minimize noise amplification effects.
Solution Approach 2:
The patent implements partial action by applying sensitivity mismatch compensation only to the extent necessary to reduce noise amplification while maintaining acceptable array gain. Rather than completely equalizing all microphone signals or applying maximum compensation, the system applies a controlled compensation factor that provides sufficient noise reduction without过度 reducing the beamforming gain, thus achieving an optimal balance between signal strength and noise suppression.
2Volume of moving object
If microphones are placed in close proximity to each other, then device size is reduced, but spatially uncorrelated noise increases
Solution Approach 1:
The patent compensates for the increased spatially uncorrelated noise from close microphone placement by applying sensitivity mismatch compensation to the beamforming coefficients. This parameter adjustment optimizes the signal combination weights to minimize the impact of close proximity noise, allowing the system to maintain small form factor while managing noise levels through computational rather than physical means.
3Device complexity
If sensitivity mismatches between microphones are not accounted for, then system complexity is reduced, but white noise gain increases
Solution Approach 1:
The patent introduces sensitivity mismatch compensation parameters that are calculated and applied to the beamforming coefficients. This adds a computational step but uses relatively simple mathematical operations (multiplication by compensation factors) that can be efficiently implemented. The increased complexity is minimal compared to the significant reduction in white noise gain achieved, making it a practical solution that balances computational load with noise suppression performance.
Data Source
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AI summary
A system that includes a microphone array comprising a plurality of microphones positioned at different locations, where the microphones output microphone signals. A beamformer is applied to the microphone output signals and is configured to control a gain that is applied to the microphone output signals. The gain is frequency dependent and is related to a mismatch in sensitivity between two or more of the microphones.