Adaptive Echo Cancellation via Position-Dependent Filter Coefficients
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Solution Overview
Problem
Existing acoustic echo cancellers take time to re-estimate the transmission function when the positions of loudspeakers and microphones change, leading to potential errors in echo removal.
Innovation Solution
A sound emitting and collecting apparatus with an adaptive filter, a detection section for movement, and a storage section to quickly set appropriate filter coefficients based on the movement of a movable microphone section, ensuring stable echo removal by pre-defining relationships between movement and filter coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an acoustic echo canceller is used to remove echo components, then echo removal function is achieved, but when the position of loudspeaker or microphone changes, the system takes time to re-estimate the transmission function and may output error signals
Solution Approach 1:
The system pre-stores multiple filter coefficients corresponding to different relative positions of loudspeaker and microphone in a storage section. When position change is detected, the corresponding pre-calculated filter coefficient is immediately retrieved and applied, eliminating the need for time-consuming re-estimation of the transmission function. This preliminary preparation of coefficients for various positions resolves the contradiction by providing instant adaptation to position changes.
Solution Approach 2:
The system dynamically switches between different filter coefficients based on the detected relative position of loudspeaker and microphone. A detection section monitors position changes and triggers selection of appropriate pre-stored coefficients. This dynamic adaptation mechanism ensures the echo canceller maintains reliability across varying positions without requiring time-consuming re-estimation, thus resolving the time loss issue.
2Measurement precision
If the transmission function is continuously re-estimated to maintain accurate echo removal, then echo removal accuracy is improved, but the system complexity and processing load increase
Solution Approach 1:
Instead of continuously re-estimating the transmission function, the system pre-calculates and stores filter coefficients for various loudspeaker-microphone relative positions. The estimation process is performed offline in advance, and only simple retrieval and selection operations are needed during actual operation. This approach maintains high echo removal accuracy while significantly reducing real-time processing complexity.
Solution Approach 2:
The system estimates transmission functions for multiple possible positions in advance (excessive action during setup), storing these coefficients for later use. During operation, only the necessary retrieval and selection of pre-computed coefficients is performed, rather than continuously re-estimating. This partial estimation approach maintains accuracy while reducing ongoing processing complexity.
Data Source
AI summary
A sound emitting and collecting apparatus that can accomplish stable echo removal if the relative positions of a loudspeaker and a microphone change is provided. A control section 52 inputs information of an arm rotation angle from a sensor 54. The control section 52 reads the filter coefficient corresponding to the input rotation angle from memory 53 and sets the coefficient in an adaptive filter 412A. When the arm rotates, the installing position of a microphone is changed and an acoustic transmission system changes, but a preset (or in the installing environment, updated) filter coefficient is set, whereby stable echo removal can be accomplished.