Position-Independent Microphone Array Using Eigenbeam Compensation
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Solution Overview
Problem
Conventional microphone arrays face challenges in maintaining high signal-to-noise ratio (SNR) in noisy environments, particularly in highly noise-contaminated settings, where farfield microphone arrays may not provide sufficient gain, and existing adaptive methods do not effectively recover losses in attenuation due to orientation changes.
Innovation Solution
A method involving a microphone array with a modal decomposer and beamformer that decomposes audio signals into eigenbeam outputs, generating compensation data for distance and orientation estimates to optimize the auditory scene, allowing for constant performance across various distances and orientations without physical array adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If farfield microphone array technology is used, then speech pick-up with high signal-to-noise ratio is achieved, but sufficient gain is not provided in highly noise-contaminated environments
Solution Approach 1:
The system dynamically adapts between farfield and nearfield processing modes based on the detected distance to the sound source. When the source is close, nearfield processing is applied to maximize gain; when far, farfield processing maintains high SNR. This dynamic adaptation resolves the contradiction by selecting the appropriate processing mode for each operating condition.
Solution Approach 2:
The system changes processing parameters (distance estimate, orientation estimate) based on the spatial position of the sound source. By estimating the distance and orientation of the source relative to the array, the system adjusts its processing characteristics to optimize both gain and SNR for the current operating conditions.
2Power
If close-talking microphone is used, then sufficient gain is achieved in noisy environments, but frequency response shows high-pass behavior for farfield sources
Solution Approach 1:
The system dynamically switches processing modes based on source distance. For nearfield sources, close-talking processing provides sufficient gain. For farfield sources, farfield processing is applied to maintain flat frequency response. This dynamic mode switching resolves the contradiction by ensuring the appropriate processing characteristics are applied for each distance regime.
3Reliability
If adaptive method with correction filter is applied, then flat frequency response is achieved for close-talking array, but loss in attenuation of farfield sources due to orientation is not recovered
Solution Approach 1:
The system changes processing parameters based on the estimated orientation of the sound source. When the source orientation relative to the array changes, the system adjusts its processing to compensate for the resulting attenuation losses. This parameter adaptation resolves the contradiction by maintaining both flat frequency response and proper attenuation characteristics across different orientations.
4Adaptability or versatility
If spherical array geometry is used, then full 3D control of beampattern is achieved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical array geometries (such as spherical arrays requiring full 3D control) with a simpler linear array configuration. Instead of using the physical geometry to achieve 3D control, the system uses signal processing techniques including distance estimation, orientation estimation, and mode-dependent processing to achieve equivalent functionality with reduced hardware complexity.
Data Source
AI summary
An audio system generates position-independent auditory scenes using harmonic expansions based on the audio signals generated by a microphone array. In one embodiment, a plurality of audio sensors are mounted on the surface of a sphere. The number and location of the audio sensors on the sphere are designed to enable the audio signals generated by those sensors to be decomposed into a set of eigenbeam outputs. Compensation data corresponding to at least one of the estimated distance and the estimated orientation of the sound source relative to the array are generated from eigenbeam outputs and used to generate an auditory scene. Compensation based on estimated orientation involves steering a beam formed from the eigenbeam outputs in the estimated direction of the sound source to increase direction independence, while compensation based on estimated distance involves frequency compensation of the steered beam to increase distance independence.