Post-Filter for Resonance-Induced Echo Distortion
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Solution Overview
Problem
Echo cancellation units in electronic devices, such as cordless and wireless telephones, face performance degradation due to distortions in the acoustic echo path caused by resonances and mechanical resonances, leading to annoying artefacts in handsfree telephone applications.
Innovation Solution
An echo suppression unit is introduced that selectively removes distortion components from the transmit signal by analyzing the receive signal for distorting frequencies and applying a post-filter to attenuate these frequencies, thereby improving echo cancellation performance and duplexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If echo cancellation units are used to remove echo from transmit signal, then echo removal is achieved, but performance decreases in presence of acoustic path distortions
Solution Approach 1:
The echo suppression unit segments the distortion component removal process by identifying specific distorting frequencies in the receive signal and applying targeted post-filters for each frequency, rather than attempting to handle all distortions uniformly. This segmentation allows the system to address specific resonance issues while maintaining overall echo cancellation performance.
Solution Approach 2:
The system performs preliminary analysis of the receive signal to detect distorting frequencies before they cause problems in the transmit signal. By identifying these frequencies in advance and preparing appropriate post-filters, the system can proactively suppress distortion components before they degrade echo cancellation performance.
2Reliability
If post-filter is applied to remove distortion components, then duplexity is improved, but device complexity increases
Solution Approach 1:
The system changes parameters by analyzing the spectral characteristics of the receive signal to identify distorting frequencies, then adapts the post-filter parameters accordingly. This parameter-based approach allows flexible distortion suppression without requiring complex hardware modifications, as the filters can be configured based on detected frequency characteristics.
Solution Approach 2:
The echo suppression unit acts as an intermediary between the echo cancellation unit and the transmit signal output. It receives the transmit signal, applies selective distortion component removal through post-filters, and outputs the cleaned signal. This intermediary approach maintains modularity and allows the distortion suppression function to be added without fundamentally redesigning the entire echo cancellation system.
3Measurement precision
If multiple post-filters are used for different distorting frequencies, then distortion removal precision is improved, but computational load increases
Solution Approach 1:
Instead of applying excessive filtering across the entire frequency spectrum, the system performs partial action by identifying specific distorting frequencies and applying post-filters only at those targeted frequencies. This selective approach removes distortion components with high precision while minimizing unnecessary computational energy expenditure on frequency regions that do not contain distortion.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively removes distortion-induced echo components from the transmit signal, enhancing duplexity and echo removal stability, even in the presence of distortions, and is computationally efficient by using time-domain filters and multiple post-filters tailored to specific distorting frequencies.
Implementation Method 1
distortions may be induced by resonances (e.g. cabinet resonances or mechanical resonances) of an electronic device
Implementation Method 2
a post-filter may be applied to the transmit signal, in order to remove the 'to-be-expected' distortion component from the echo of the receive signal
Data Source
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AI summary
The present document relates to echo cancellation and/or echo suppression. In particular, the present document relates to a method and system for improving echo suppression and/or duplexity of handsfree telephone applications. An echo suppression unit (203) for an electronic device (100) comprising a loudspeaker (107) and a microphone (105) is described. The microphone (105) is configured to capture a transmit signal (223), wherein the transmit signal (223) comprises an echo of a receive signal (220) rendered by the loudspeaker (107). The echo suppression unit (203) is configured to determine, based on the receive signal (220), whether the receive signal (220) comprises a first frequency component (310) causing the echo of the receive signal (220) to comprise a distortion component (311). The distortion component (311) comprises one or more frequencies which are not comprised within the first frequency component (310). Furthermore, the echo suppression unit (203) is configured to apply a post-filter (303) to the transmit signal (223), if it is determined that the receive signal (220) comprises the first frequency component (310). The post-filter (303) is configured to selectively attenuate the distortion component (311).