Interference Suppression Using Frequency-Dependent Decay Factors
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Solution Overview
Problem
In-car communication systems face challenges in speech intelligibility due to background noise and interference from audio playback and system feedback, making it difficult to suppress these interferences effectively, especially in vehicles where noise levels are high.
Innovation Solution
A method using an energy decay model with frequency-dependent coupling, decay, and delay factors to estimate interference signals, allowing for independent or combined suppression of communication system feedback, audio system feedback, and noise, ensuring consistent interference suppression and improving signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If adaptive filters are used to cancel feedback and noise signals, then interference suppression is achieved, but the strong correlation between feedback signal and local speech signal disturbs filter adaptation
Solution Approach 1:
The patent segments the interference suppression task into multiple independent filters, each targeting specific interference sources (feedback signal, noise, audio playback) rather than using a single adaptive filter. This segmentation allows each filter to specialize in canceling particular interference types, avoiding the adaptation disturbances caused by strong correlations in unified filter approaches.
Solution Approach 2:
The patent introduces an intermediary mechanism where multiple specialized filters act as mediators between the microphone signal and the processed output. Each filter processes specific interference components independently, allowing stable adaptation for each interference type while maintaining overall system performance.
2Illumination intensity
If multiple channel audio playback is used, then audio quality is improved, but echo cancellation becomes extremely challenging due to strong correlation between channels
Solution Approach 1:
The patent applies segmentation by creating separate echo cancellation filters for each audio channel rather than attempting to cancel all channels simultaneously with a single filter. This allows each filter to handle one channel's echo independently, significantly reducing the complexity of multi-channel echo cancellation while maintaining high audio quality.
3Loss of information
If interference suppression is applied, then speech intelligibility is improved, but the signal output level of processed speech and residual interferences is affected
Solution Approach 1:
The patent employs feedback mechanisms where the output of each suppression filter is monitored and used to adjust subsequent processing stages. This feedback loop allows the system to maintain speech intelligibility improvements while compensating for output level changes and residual interference effects through dynamic gain adjustment.
Solution Approach 2:
The patent dynamically changes processing parameters including gain factors and filter coefficients based on the detected signal conditions. By adjusting these parameters in response to the processed signal characteristics, the system maintains optimal speech intelligibility while compensating for output level variations introduced by interference suppression.
Data Source
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AI summary
In a method for interference suppression for a communication system as an indoor communication system or a handsfree telephony system or an automatic speech recognition system, at least one loudspeaker and at least one microphone are provided, particularly in a vehicle. A test signal is sent for determining system characteristics on the base of the test signal received by a microphone. The interference may be an ICC-system feedback component or the feedback signal of the audio component. The system characteristics detected by the test signal are used to determine interference model parameters in the form of frequency dependent coupling factors and frequency dependent decay factors and frequency dependent delay factors. Then, an estimated interference signal is formed on the base of the sub-band coupling factor times the magnitude square of a sub-band delayed loudspeaker signal plus a last interference signal level times a sub-band decay. The estimated interference signal is used to suppress the interference signal accordingly.