Spatial Filter Noise Reduction for Low SNR Audio
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Solution Overview
Problem
Current noise reduction techniques for microphone signals require a certain signal-to-noise ratio and stationary noise statistics, limiting their effectiveness, especially in low signal-to-noise environments.
Innovation Solution
A signal processing device using a combination of beamformers and power estimators to generate statistical energy estimates of sound fields, allowing for noise reduction at low signal-to-noise ratios by processing signals from multiple microphones and applying adaptive gain control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single microphone noise reduction techniques are used, then the device complexity is reduced, but the noise reduction performance deteriorates at low signal-to-noise ratios
Solution Approach 1:
The patent segments the sound field into different spatial regions (first part and second part) using multiple beamformers. Each beamformer processes microphone signals to create beamformed signals, and the power estimator calculates statistical energy estimates for different spatial regions. This segmentation allows the system to distinguish between signal and noise components more effectively, improving noise reduction performance without requiring excessive complexity.
Solution Approach 2:
The patent introduces a spatial dimension by using multiple beamformers with different beam directions. Instead of processing only temporal or frequency information, the system adds spatial information through beamforming. This dimensional expansion enables the system to exploit spatial correlations between microphones to improve noise reduction, particularly at low signal-to-noise ratios.
2Reliability
If multiple beamformers and power estimators are used to improve noise reduction at low signal-to-noise ratios, then the noise reduction performance is improved, but the device complexity increases
Solution Approach 1:
The power estimator serves multiple functions: it processes beamformed signals from different beamformers, calculates statistical energy estimates for different spatial regions, and provides input for gain control. This multi-functionality reduces the need for separate dedicated components for each function, thereby managing device complexity while maintaining improved noise reduction performance.
Solution Approach 2:
The patent implements a feedback mechanism where the power estimator continuously monitors the energy distribution in different spatial regions and feeds this information back to the gain controller. The gain controller adjusts the gain signals based on this feedback, creating a closed-loop system that adapts to changing acoustic conditions. This feedback mechanism improves noise reduction performance while keeping the system manageable through intelligent control rather than excessive hardware complexity.
Data Source
AI summary
A device and method processing microphone signals from at least two microphones is presented. A first beamformer processes the signals from the microphones and provides a first beamformed signal. A power estimator processes the signals from the microphones and the first beamformed signal from the first beamformer in order to generate, in frequency bands, a first statistical estimate of the energy of a first part of an incident sound field. A gain controller processes said first statistical estimate in order to generate in frequency bands a first gain signal, and an audio processor for processing an input to the signal processing device in dependence of said generated first gain signal. The invention provides a new and improved noise reduction device and noise reduction method for use in the signal processing in devices processing acoustic signals, e.g. microphone devices.