Microphone Array Spatial Noise Suppression for Low SNR
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Solution Overview
Problem
Mobile devices, such as phones and PDAs, often experience a low signal-to-noise ratio (SNR) when used in hands-free mode or with headsets due to suboptimal microphone placement, leading to decreased speech signal quality in noisy environments.
Innovation Solution
A microphone array with at least three microphones uses spatial noise suppression by estimating the desired signal through spatio-temporal distribution, updating signal and noise variance models based on the presence of speech, and employing a speech activity detector to adapt these models in a multi-dimensional space defined by the microphone signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the microphone is placed away from the user's mouth for comfort and convenience, then the device is easier to operate, but the signal-to-noise ratio deteriorates
Solution Approach 1:
The single microphone function is segmented into multiple microphones working in an array configuration. This allows the system to maintain comfortable headset positioning while using multiple sensors to spatially filter and enhance the speech signal, thereby improving SNR without compromising ease of operation
Solution Approach 2:
Signal processing algorithms act as an intermediary between the physically distant microphone and the user's speech. The algorithms process the captured signals to extract and enhance speech components while suppressing noise, effectively bridging the gap between comfortable positioning and signal quality
2Device complexity
If a single microphone is used to keep the device simple, then the device complexity is reduced, but the noise reduction capability deteriorates
Solution Approach 1:
The audio capture function is divided among multiple microphones in an array, with each microphone capturing spatial information from different positions. This segmentation enables spatial noise suppression through algorithms that analyze phase and amplitude differences across the array, improving noise reduction capability while maintaining manageable device complexity through systematic processing
3Measurement precision
If the microphone is positioned close to the mouth for optimal signal capture, then the signal-to-noise ratio is improved, but the ease of operation deteriorates
Solution Approach 1:
The system transitions from a single-point microphone position to a multi-dimensional spatial array configuration. By distributing microphones across multiple positions in space, the system captures speech from different spatial perspectives, enabling sophisticated noise suppression algorithms to identify and enhance speech signals while maintaining comfortable headset positioning
Data Source
AI summary
A microphone array having at least three microphones provides a captured signal. Spatial noise suppression estimates a desired signal from a captured signal using spatio-temporal distribution of the speech and the noise. In particular, spatial information indicative of at least two quantities of direction are used. A first quantity is based on a first combination of the signals from the at least three microphones, a second quantity is based on a second combination of the signals of the at least three microphones.