Full Band Canceller for Close-Coupled Acoustic Echo Suppression
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Solution Overview
Problem
Existing acoustic echo cancellation systems in close-coupled speaker and microphone systems face challenges with large echo power and dominant echo signals, leading to reduced performance and inaccurate double talk detection, especially in hands-free telecommunication systems.
Innovation Solution
The implementation of a full band canceller (FBC) and subband acoustic echo cancellation (AEC) using a combination of fixed and adaptive filters to suppress direct and residual echoes, with the FBC operating in the time domain and subband AEC in the frequency domain, to effectively cancel echoes in close-coupled systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If subband AEC filters are used to minimize echo component, then computational cost is reduced and convergence speed is improved, but AEC performance drops dramatically when echo power increases
Solution Approach 1:
The patent divides the AEC system into two segments: a full-band canceller (FBC) that handles large echo power components and a subband AEC filter that handles residual echo cancellation. This segmentation allows each component to operate in its optimal performance range, resolving the contradiction between convergence speed and AEC performance under high echo conditions.
Solution Approach 2:
The FBC performs partial echo cancellation by removing the dominant echo component before the subband AEC filter processes the residual echo. This partial action approach ensures that the subband filter operates on reduced echo power, maintaining both computational efficiency and high AEC performance.
2Ease of operation
If echo power increases in close-coupled systems, then hands-free operation is enabled, but AEC performance drops and aliasing deteriorates the system performance
Solution Approach 1:
The FBC performs preliminary echo cancellation by removing the dominant echo component before the signal is processed by the subband AEC filter. This preliminary action prevents aliasing from deteriorating performance and ensures that subsequent processing operates on reduced echo power, maintaining high AEC performance in hands-free operation.
3Adaptability or versatility
If echo is the dominant signal, then close-coupled system operation is achieved, but double talk detection becomes less accurate and near-end speech detection is difficult
Solution Approach 1:
The FBC performs preliminary removal of the dominant echo component from the microphone signal. This preliminary action reduces the echo power level, enabling more accurate double talk detection and near-end speech detection by the subsequent processing stages, while maintaining close-coupled system operation.
Data Source
AI summary
Embodiments are directed towards providing acoustic echo cancellation in a closely-coupled microphone/speaker system. A speaker may produce an audible signal from a reference signal, which may be captured with a microphone. Full band cancellation (FBC) may modify the captured signal to suppress an echo of the reference signal caused by a direct acoustic path between the microphone and speaker. FBC may include a fixed filter and an adaptive filter. The fixed filter may modify the captured signal based on the reference signal. The adaptive filter may automatically adapt based on the captured signal and the reference signal. If a comparison of a performance of the adaptive filter and the fixed filter is above a threshold, then the fixed filter may be updated based on the adaptive filter. Subband acoustic echo cancellation may generate an output signal that suppresses residual echoes of the reference signal based on the modified signal.