Dual Echo Cancellation with Room Change Detection
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Solution Overview
Problem
Existing acoustic echo cancellation systems face challenges in efficiently adapting to changes in acoustic environments, such as room changes, which can lead to prolonged convergence times and misadjustment issues due to the trade-off between adaptation speed and accuracy.
Innovation Solution
The proposed solution involves a dual-echo canceller system with a main adaptive echo canceller and a shadow non-adaptive echo canceller, where the shadow canceller operates at a higher adaptation step size to quickly adapt to room changes, and a room change detector evaluates error signals to switch coefficients between the two, ensuring fast adaptation without freezing or misadjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If adaptive filtering algorithm is used to model transfer function, then echo cancellation accuracy is improved, but convergence time increases when room changes occur
Solution Approach 1:
The system divides the echo canceller into two independent parts: a main adaptive echo canceller for accurate echo modeling under stationary conditions, and a shadow non-adaptive echo canceller for rapid response to room changes. This segmentation allows each component to specialize in different functions, resolving the contradiction between accuracy and convergence speed.
Solution Approach 2:
The system changes the adaptation parameter (step size) dynamically based on room change detection. When room changes are detected, the shadow canceller uses a larger step size to quickly track the new acoustic path, while the main canceller maintains stable adaptation. This parameter change strategy enables fast convergence without sacrificing accuracy during normal operation.
2Speed
If adaptation speed is increased to respond to room changes, then convergence rate is improved, but misadjustment occurs during transient states
Solution Approach 1:
By segmenting the echo canceller into main and shadow components with different adaptation characteristics, the system achieves high adaptation speed through the shadow canceller while maintaining reliability through the main canceller's stable adaptation. The room change detector coordinates their operation to prevent misadjustment during transitions.
Solution Approach 2:
The room change detector provides feedback about acoustic environment changes to coordinate the behavior of main and shadow echo cancellers. This feedback mechanism enables the system to adjust its adaptation strategy in real-time, increasing speed when needed while preventing misadjustment during transient states through coordinated control.
3Measurement precision
If dual-echo canceller system is implemented, then room change detection accuracy is improved, but device complexity increases
Solution Approach 1:
The system merges the main adaptive echo canceller and shadow non-adaptive echo canceller into a unified dual-echo canceller architecture. Both cancellers share common components such as the room change detector and coefficient storage, reducing the overall complexity increase while maintaining high room change detection accuracy through coordinated operation.
Data Source
AI summary
Acoustic echo cancelling includes receiving a source signal and a sink signal; providing a first error signal representative of an echo-free residual signal based on a first set of coefficients based on the source signal and the sink signal, the first error signal forming an output signal of the controller; providing a second error signal based on a second set of coefficients based on the source signal and the sink signal; detecting a room change if the evaluated first second error signal is greater than a sum or product of the evaluated second first error signal and a first threshold; copying one of sets of reference coefficients stored in a memory to the second acoustic echo canceller; and copying the first set of coefficients from the first acoustic echo canceller as a set of reference coefficients into at least one of the second acoustic echo canceller and the memory.