Acoustic Echo Canceller Adaptation for Loudspeaker Distortion
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Solution Overview
Problem
Hands-free communication systems face challenges in echo cancellation due to distortion introduced by loudspeakers, leading to faulty echo cancellation and poor voice quality, particularly when loudspeaker non-linear distortion violates the linear assumptions of echo cancellers and results in echo leakage.
Innovation Solution
The method involves determining an external gain value associated with the far-end audio signal and adjusting parameters of the acoustic echo canceller and non-linear compressor based on this value to minimize distortion, using techniques such as multiband limiting and adjusting echo return loss, adaptive filter step-size, and filter coefficients, to ensure effective echo cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If loudspeaker playback is used for hands-free communication, then voice transmission capability is improved, but non-linear distortion is introduced causing echo cancellation failure
Solution Approach 1:
The system dynamically adapts the echo canceller parameters based on detected loudspeaker distortion characteristics. The echo canceller transitions from static linear filtering to dynamic adaptive filtering that adjusts its behavior based on real-time distortion measurements, allowing it to effectively cancel echo even when the loudspeaker introduces non-linear distortions.
Solution Approach 2:
The invention changes the operational parameters of the echo canceller to account for loudspeaker non-linearities. By measuring distortion products and adjusting echo canceller parameters accordingly, the system maintains effective echo cancellation performance across different loudspeaker operating conditions and distortion levels.
2Measurement precision
If external gain is increased to improve voice quality, then downlink speech quality is improved, but playback distortion increases causing echo leakage
Solution Approach 1:
The system implements a feedback mechanism where distortion products generated by the loudspeaker are detected and used to adjust echo canceller parameters. This closed-loop approach allows the system to maintain optimal echo cancellation performance even when external gain is increased, preventing echo leakage while preserving voice quality.
Solution Approach 2:
The system performs preliminary distortion measurement and echo canceller parameter adjustment before echo leakage becomes problematic. By proactively adapting to anticipated distortion based on external gain settings, the system prevents echo leakage rather than reacting to it after occurrence.
Data Source
AI summary
A method of echo cancellation in hands-free communication is disclosed. The method includes: receiving, via a receive signal processor, a far-end audio signal; providing the far-end audio signal to: an acoustic echo canceller module as a reference signal, and at least one loudspeaker for playback; determining an external gain value associated with the far-end audio signal, the external gain applied to the far-end audio signal downstream of the receive signal processor and prior to playback from the at least one loudspeaker; adjusting at least one parameter of the acoustic echo canceller module based on the external gain value; receiving playback output of the far-end audio signal from the at least one loudspeaker as an input signal to a microphone; and processing the microphone input signal by the adjusted acoustic echo canceller module to produce an echo-cancelled signal.