Multiple Microphone Noise Reduction via Blind Source Separation
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Solution Overview
Problem
Existing audio processing technologies in mobile devices struggle to effectively reduce background noise and acoustic echo in multiple microphone systems without distorting the desired speech, especially when dealing with non-stationary noise and requiring multiple microphones, which can be costly and limit device usage.
Innovation Solution
A multiple microphone noise and echo reduction system that uses echo cancellers, blind source separation, and non-linear processing to separate speech signals from noise, incorporating pre-processing de-correlation and post-filtering to enhance speech quality and reduce residual noise and echo.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spectral subtraction is used to suppress background noise in single-microphone systems, then stationary noise reduction is achieved, but non-stationary noise cannot be reduced and speech distortion occurs
Solution Approach 1:
The patent segments the noise reduction task by using multiple microphones to capture different acoustic perspectives. Each microphone signal is processed independently through echo cancellation and noise reduction, then combined through beamforming to achieve both stationary and non-stationary noise reduction while preserving speech quality
Solution Approach 2:
The patent transitions from single-microphone frequency-domain processing to multi-microphone spatial-domain processing. By adding the spatial dimension with multiple microphones arranged in specific geometries, the system can distinguish speech from noise based on spatial characteristics, enabling effective non-stationary noise reduction
2Object-affected harmful factors
If uni-directional microphones are used for noise reduction, then noise suppression performance is improved, but device cost increases and usage flexibility is limited
Solution Approach 1:
The patent makes omni-directional microphones perform multiple functions: they capture both speech and noise, and through signal processing (beamforming and spatial filtering), the same hardware configuration achieves noise suppression without requiring expensive uni-directional microphones or strict placement constraints
Solution Approach 2:
The patent replaces the mechanical solution of using expensive uni-directional microphones with a signal processing solution. Instead of relying on microphone directional characteristics, the system uses digital signal processing (beamforming, spatial filtering) to achieve noise suppression, substituting mechanical complexity with computational complexity
3Object-affected harmful factors
If aggressive echo cancellation algorithms are used, then acoustic echo is reduced, but communication is restricted to half-duplex mode reducing productivity
Solution Approach 1:
The patent introduces multiple microphones as intermediaries to capture acoustic echo from different spatial positions. By processing these multiple signals through beamforming and spatial filtering, the system can identify and suppress echo while maintaining full-duplex communication, as the microphones provide additional spatial information that aids echo discrimination
4Measurement precision
If multiple microphones are used for noise and echo reduction, then speech intelligibility is improved, but device complexity and cost increase
Solution Approach 1:
The patent segments the complex noise and echo reduction task into independent processing stages for each microphone signal (echo cancellation, noise reduction), then combines them through beamforming. This modular segmentation makes the multiple microphone system more manageable and less complex than attempting simultaneous processing
Data Source
AI summary
Multiple microphone noise suppression apparatus and methods are described herein. The apparatus and methods implement a variety of noise suppression techniques and apparatus that can be selectively applied to signals received using multiple microphones. The microphone signals received at each of the multiple microphones can be independently processed to cancel echo signal components that can be generated from a local audio source. The echo cancelled signals may be processed by some or all modules within a signal separator that operates to separate or otherwise isolate a speech signal from noise signals. The signal separator can include a pre-processing de-correlator followed by a blind source separator. The output of the blind source separator can be post filtered to provide post separation de-correlation. The separated speech and noise signals can be non-linearly processed for further noise reduction, and additional post processing can be implemented following the non-linear processing.