Echo Canceller Convergence Control via Dual Adaptation Factor Selection
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Solution Overview
Problem
Existing echo cancellers in vehicular environments face challenges in achieving accurate convergence control due to rapid acoustic changes and high noise energy, leading to incomplete echo cancellation and user dissatisfaction.
Innovation Solution
The use of a free-running echo canceller filter in conjunction with Microphone Error Cross Correlation (MECC) and Normalized Echo Return Loss (NERL) estimates to generate an adaptation factor for the echo cancelling filter, allowing for improved convergence control by continuously adapting to the environment and selecting the appropriate adaptation factor based on predetermined criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional echo cancellers are used in vehicular environments, then echo attenuation is provided, but convergence accuracy deteriorates due to rapid acoustic changes and high noise energy
Solution Approach 1:
The patent implements dynamic adaptation factor selection by continuously comparing MECC and NERL estimates and selecting the more reliable one in real-time. This allows the echo canceller to adapt its convergence behavior dynamically based on current acoustic conditions, resolving the contradiction between maintaining cancellation accuracy and adapting to changing environments.
Solution Approach 2:
The patent changes the adaptation parameter (convergence factor) based on environmental conditions by using two different estimation methods (MECC and NERL) that are selected according to the acoustic situation. This parameter adaptation resolves the contradiction by adjusting the convergence behavior to match the reliability of the current acoustic environment.
2Adaptability or versatility
If convergence control adapts quickly to rapid acoustic changes, then adaptability improves, but convergence accuracy deteriorates due to high noise energy
Solution Approach 1:
The patent uses feedback from two independent estimation methods (MECC and NERL) to determine the appropriate adaptation factor. By continuously monitoring both estimates and selecting based on their relative reliability, the system achieves fast adaptation while maintaining precision through the feedback-driven selection mechanism.
Solution Approach 2:
The patent employs partial adaptation by using only the more reliable of the two estimation methods at any given time, rather than combining both equally. This selective partial action allows the system to adapt quickly when conditions permit while avoiding noise-induced errors when conditions are poor.
3Object-generated harmful factors
If echo canceller provides strong attenuation, then echo suppression improves, but speech quality deteriorates due to incomplete cancellation and residual echo
Solution Approach 1:
The patent dynamically changes the adaptation parameter based on the reliability of convergence control estimates. When the acoustic environment is noisy or changing rapidly, the system reduces adaptation to prevent residual echo and speech distortion, thereby maintaining speech quality while still providing adequate echo attenuation.
Data Source
AI summary
Regardless of the presence of echo or uplink speech, a microphone signal is received at a small filter and this small filter is functionally and/or physically separate from an adaptive echo canceller filter. The signal is applied to the small filter and an error signal is determined from the signal utilizing the small filter. The small filter continuously adapts the received signals. A first adaptation factor is determined based at least upon the error signal and the microphone signal according to a first signal analysis approach and a second adaptation factor is determined based at least upon the microphone signal according to a second signal analysis approach. The first adaption factor is compared to the second adaptation factor and one of the first adaptation factor or the second adaptation factor is selected based upon at least one predetermined criteria. The selected adaptation factor is applied to the echo canceller filer to control the convergence of the echo canceller filter.