Echo Suppression via Late Reverberation Modeling
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Solution Overview
Problem
Current echo suppression systems in conference systems, such as telephone and video conferencing, often fail to optimally handle different sound, tone, and noise components, leading to non-optimum echo suppression and the occurrence of tonal artifacts, which are distracting and annoying.
Innovation Solution
The system employs an echo decay modeling approach to compute filter coefficients for an adaptive filter, distinguishing between early and late echo components and using echo decay parameters to estimate and suppress echoes, thereby improving audio quality and reducing computational effort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional adaptive filters are used for echo suppression, then echo cancellation is achieved, but tonal artifacts occur and audio quality deteriorates
Solution Approach 1:
The patent segments the echo signal into early echo components and late reverberation components. Early echoes are suppressed using conventional adaptive filters, while late reverberation is handled separately through spectral subtraction or modeling techniques. This segmentation allows different processing strategies to be applied to different echo components, preventing the tonal artifacts that occur when a single uniform filter is applied to all echo components.
Solution Approach 2:
The patent applies different suppression characteristics to different frequency bands and time regions. Early echoes in certain frequency ranges are suppressed with aggressive filtering, while late reverberation is suppressed more gently using spectral modeling. This local differentiation of suppression quality prevents uniform over-suppression that causes tonal artifacts while maintaining effective echo cancellation where needed.
2Reliability
If aggressive echo suppression is applied, then echo cancellation improves, but audio quality and naturalness deteriorate
Solution Approach 1:
The patent dynamically adjusts suppression strength based on the temporal and spectral characteristics of the echo signal. During periods with strong direct echo, aggressive suppression is applied. During periods with predominant late reverberation, gentler suppression is used to preserve natural audio quality. This dynamic adaptation prevents consistent over-suppression that degrades audio quality while maintaining effective echo cancellation when necessary.
Solution Approach 2:
The patent changes suppression parameters based on the estimated echo characteristics. When late reverberation is detected, spectral modeling parameters are adjusted to match the reverberation decay characteristics, allowing effective suppression without the harsh artifacts of fixed aggressive filtering. This parameter adaptation maintains audio quality while achieving reliable echo cancellation.
3Measurement precision
If detailed modeling of all echo components is performed, then suppression accuracy improves, but computational complexity increases
Solution Approach 1:
The patent segments echo modeling into two distinct stages: early echo estimation using efficient adaptive filtering with low computational requirements, and late reverberation estimation using spectral modeling with moderate complexity. This segmentation achieves comprehensive echo estimation accuracy without requiring equally complex processing for all echo components, thus managing overall computational complexity effectively.
Solution Approach 2:
The patent creates a spectral model of the late reverberation characteristics based on observed signal properties, rather than performing exhaustive convolution or full impulse response modeling. This copying approach captures the essential characteristics of late reverberation with significantly reduced computational complexity while maintaining sufficient estimation accuracy for effective suppression.
Data Source
AI summary
An apparatus for computing filter coefficients for an adaptive filter is disclosed. The adaptive filter is used for filtering a microphone signal so as to suppress an echo due to a loudspeaker signal. The apparatus has: an echo decay modeling means for modeling a decay behavior of an acoustic environment and for providing a corresponding echo decay parameter; and computing means for computing the filter coefficients of the adaptive filter on the basis of the echo decay parameter. A corresponding method has: providing echo decay parameters determined by means of an echo decay modeling means; and computing the filter coefficients of the adaptive filter on the basis of the echo decay parameters.