Audio Apparatus Nonlinear Echo Cancellation
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Solution Overview
Problem
Existing audio systems face challenges in effectively canceling acoustic echoes due to nonlinear characteristics of loudspeakers, which are not adequately addressed by current echo cancellation methods, leading to suboptimal performance and high computational complexity.
Innovation Solution
An audio apparatus and method that apply dynamic range adjustment processing to input signals, using adaptive filters and dynamic range adjustment parameters to generate compensated signals, allowing for improved linearization of loudspeaker operation without requiring specific knowledge of the loudspeaker or amplifier characteristics, and automatically adapting to changes in the audio chain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If linear echo cancellation is used, then echo cancellation performance is improved, but the inability to model nonlinear loudspeaker characteristics causes residual echo and suboptimal performance
Solution Approach 1:
The patent segments the echo cancellation system into two independent parts: a linear echo canceller that handles linear acoustic path and a nonlinear distortions canceller that handles loudspeaker nonlinearities. This segmentation allows each component to specialize in its specific function, with the linear part dealing with acoustic reflections and the nonlinear part dealing with distortion products, thereby resolving the contradiction between linear cancellation effectiveness and nonlinear modeling capability.
Solution Approach 2:
The patent introduces an intermediary approach by using a Volterra series expansion model that captures nonlinear distortions separately from the linear acoustic path. This intermediary modeling technique allows the system to account for nonlinear loudspeaker characteristics without interfering with the linear echo cancellation process, enabling both high reliability in echo cancellation and accurate modeling of nonlinear behaviors.
2Reliability
If Volterra series expansion is used to model loudspeaker nonlinearities, then nonlinear echo cancellation is improved, but computational complexity increases significantly
Solution Approach 1:
The patent segments the computational burden by separating linear and nonlinear cancellation into independent processing paths. The linear echo canceller handles the computationally intensive linear acoustic path modeling, while the nonlinear distortions canceller handles only the nonlinear loudspeaker characteristics. This segmentation reduces the overall computational complexity compared to a single unified nonlinear model.
Solution Approach 2:
The patent extracts the nonlinear distortion modeling from the main echo cancellation process and places it in a separate canceller module. By taking out the nonlinear processing as a distinct function that operates on residual signals after linear cancellation, the system reduces computational complexity while maintaining accurate nonlinear echo cancellation performance.
3Reliability
If power series expansion with signal orthogonalization is used, then nonlinear distortion modeling is improved, but computational intensity increases
Solution Approach 1:
The patent segments the signal processing into distinct linear and nonlinear stages, where the nonlinear distortions canceller processes only the residual signal containing nonlinear distortions after linear cancellation. This segmentation reduces the computational intensity required for nonlinear modeling compared to processing the entire signal through complex orthogonalization procedures.
Solution Approach 2:
The patent applies partial action by using power series expansion only for modeling nonlinear distortions rather than attempting to model the entire acoustic path including linear components. This selective application of complex modeling only where needed (for nonlinear distortions) improves computational efficiency while maintaining accurate nonlinear distortion modeling.
4Power
If loudspeaker is driven to high output levels, then sound output quality is improved, but nonlinear distortions increase and echo cancellation performance degrades
Solution Approach 1:
The patent implements feedback by continuously monitoring the microphone signal and using it to adaptively adjust the echo cancellation filters. The feedback loop detects nonlinear distortions in real-time and updates the distortions canceller parameters, allowing the system to maintain high echo cancellation performance even when the loudspeaker operates at high output levels with inherent nonlinearities.
Solution Approach 2:
The patent introduces an intermediary nonlinear distortions canceller that acts as a mediator between the high-power loudspeaker output and the echo cancellation process. This intermediary component compensates for nonlinear distortions introduced by high-power operation, allowing the system to achieve both high sound output levels and reliable echo cancellation performance simultaneously.
Data Source
AI summary
An audio apparatus including a circuit for applying a dynamic range adjustment processing to an input signal to generate an output signal for rendering by a loudspeaker. The dynamic range adjustment processing is dependent on a set of dynamic range adjustment parameters. A first linear echo-cancellation filter generates a first compensated signal from the input signal and a first adapter determines a set of filter parameters for the first linear echo-cancellation filter in response to the first compensated signal and a microphone signal. An audio circuit generates a second compensated signal by applying the dynamic range adjustment processing and a second echo-cancellation filter to the input signal where the second echo-cancellation filter corresponding to the first echo-cancellation filter. A second adapter determines the set of dynamic range adjustment parameters in response to the second compensated signal and the microphone signal.