Acoustic Echo Canceller Adaptation for Wideband Path Changes

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Solution Overview

Problem

Echo cancellers struggle to adapt quickly to external changes in the echo path, such as volume adjustments, leading to prolonged echo bursts and compromised echo reduction performance.

Innovation Solution

A method for echo cancellation that involves detecting a wideband offset between a reference signal and an output signal by comparing their spectra, applying compensation gains to prediction filter coefficients, and adapting the echo cancellation system to quickly adjust to changes in the echo path.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If conventional adaptation mechanisms (LMS, NLMS, PNLMS) are used to adapt prediction filter coefficients, then echo cancellation can operate with manageable complexity, but the system responds slowly to external changes in the echo path (e.g., volume adjustments)

Engineering Contradiction:

ImproveAdaptation speed to echo path changesVSAvoidTime duration of echo bursts during adaptation

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The system performs preliminary detection of echo path changes by monitoring for wideband offsets in the microphone signal before full adaptation is needed. This early detection triggers preparatory actions that accelerate the subsequent adaptation process, reducing the time echo bursts persist when volume changes occur

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback by continuously monitoring the microphone signal for wideband offsets and using this information to control the adaptation process. When a wideband offset is detected, the system adjusts prediction filter coefficients more aggressively, creating a feedback loop that accelerates convergence and reduces echo burst duration

Inventive Principle:

Principle #23Feedback

2Speed

If the prediction filter is adapted aggressively to speed up response to echo path changes, then adaptation speed improves, but the system may become unstable or produce incorrect adaptations

Engineering Contradiction:

ImproveAdaptation speed to echo path changesVSAvoidStability of adaptation process

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The system applies different adaptation strategies to different parts of the frequency spectrum. Wideband offsets detected in the microphone signal trigger aggressive adaptation specifically targeted at the detected frequency regions, while other frequency regions maintain more conservative adaptation. This localized approach allows fast response where needed while maintaining overall stability

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The system dynamically adjusts the adaptation step size and convergence criteria based on the detected wideband offset characteristics. When wideband offsets are detected indicating echo path changes, the system temporarily increases adaptation aggressiveness. When no wideband offsets are present, the system uses conventional conservative adaptation, creating a dynamic adaptation process that balances speed and stability

Inventive Principle:

Principle #15Dynamics

Data Source

PatentEP4121961B1Wideband adaptation of echo path changes in an acoustic echo canceller

Publication Date: 2025.10.08 DOLBY LABORATORIES LICENSING CORP

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AI summary

Systems, methods, and computer program products for echo cancellation with prediction filter adaptation and detection of wideband offset between a reference signal (available to the echo canceller) and an output signal (unavailable to the echo canceller), where the output signal has been generated by applying at least one level shift to the reference signal, e.g. such that the level shift is unknown to the echo canceller.