Multi-Channel Residual Echo Suppression via Spectral Post Filtering
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Solution Overview
Problem
Conventional acoustic echo cancelers fail to completely remove echo signals in microphone signals, especially in multi-channel audio systems, due to spectral mismatches between the echo cancelation filter coefficients and the actual echo path, leading to residual echo that interferes with user voice signals.
Innovation Solution
A method and system that employ a spectral post filter to suppress residual echo by calculating and applying filter coefficients based on spectral mismatches, using cross power spectral density and power spectral densities of audio signals and residual signals, even during double-talk conditions, to enhance the speech content and reduce non-speech content in the microphone signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional acoustic echo cancelers are used, then echo signals can be reduced, but residual echo remains due to spectral mismatch between filter coefficients and actual echo path
Solution Approach 1:
The system uses feedback by continuously monitoring the residual signal and adjusting the post-filter coefficients based on the spectral mismatch between the echo canceler output and the actual microphone signal. The spectral correlation calculation provides feedback to optimize the post-filter parameters in real-time, reducing residual echo while preserving speech quality.
Solution Approach 2:
The invention changes parameters by dynamically adjusting the post-filter coefficients based on spectral correlation analysis. The system calculates spectral mismatch metrics and uses these to modify filter parameters, transforming the static echo cancelation approach into a dynamic adaptive system that responds to changing acoustic conditions.
2Measurement precision
If residual echo suppressors are applied, then speech quality can be improved, but they are designed for single audio content channel and cannot handle multiple correlated or uncorrelated audio source signals
Solution Approach 1:
The post-filter design achieves universality by being capable of processing multiple audio content channels simultaneously, whether correlated or uncorrelated. The spectral correlation calculation method is generalized to handle arbitrary numbers of channels, making the system applicable to various multi-channel configurations without requiring separate processing paths.
Solution Approach 2:
The system segments the multi-channel signal processing into independent spectral correlation calculations for each channel, followed by a combined post-filtering stage. This segmentation allows each channel to be processed individually while maintaining the ability to handle correlations between channels, improving both computational efficiency and adaptability.
3Ease of manufacture
If echo cancelation filter coefficients are used, then echo path modeling can be achieved, but mismatch with actual echo path results in incomplete echo removal
Solution Approach 1:
The post-filter acts as an intermediary between the echo canceler output and the final microphone signal. It compensates for the imperfections in echo path modeling by providing an additional filtering stage that addresses the spectral mismatch, thereby improving the completeness of echo removal without requiring changes to the underlying echo cancelation algorithm.
Data Source
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AI summary
Audio systems and methods for suppressing residual echo are provided. First and second audio program content signals are received, and a residual signal from an echo canceler is received. A first spectral mismatch is determined based at least upon a cross power spectral density of the first program content signal and the residual signal. A second spectral mismatch is determined based at least upon a cross power spectral density of the second program content signal and the residual signal. The residual signal is filtered to reduce residual echo, based at least upon the first spectral mismatch, the second spectral mismatch, a spectral density of the first program content signal, a spectral density of the second program content signal, and a spectral density of the residual signal.