Echo Reduction System Using Sub-band Filtering and Speech Activity Detection
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Solution Overview
Problem
Existing echo suppression systems are unreliable in time-varying 'loudspeaker-room-microphone' environments, particularly in mobile communication scenarios, leading to residual echoes that interfere with communication.
Innovation Solution
A filter bank separates microphone output signals into sub-bands, with an echo compensation filter generating an estimated echo signal that is subtracted from the microphone output, and a residual echo reduction circuit using speech activity detection to suppress remaining echoes, employing adaptive filtering and Wiener filter techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing echo suppression techniques are applied, then echo suppression is attempted, but residual echoes remain and communication quality deteriorates
Solution Approach 1:
The patent divides the echo suppression system into multiple independent modules: filter bank for signal separation, echo compensation filter for echo estimation, speech activity detector for speech detection, and residual echo reduction circuit for final cleanup. Each module processes specific aspects of the signal independently, allowing comprehensive echo suppression while maintaining reliability.
Solution Approach 2:
The system employs feedback mechanisms where the speech activity detector continuously monitors the processed signal and feeds this information back to the residual echo reduction circuit. This feedback loop allows the system to adapt to changing speech conditions and dynamically adjust echo suppression strength, preventing residual echoes while avoiding interference with legitimate speech.
2Object-generated harmful factors
If echo suppression is applied in time-varying LRM environments, then echo reduction is attempted, but system performance becomes unreliable
Solution Approach 1:
The patent implements dynamic adaptation to time-varying LRM environments through the speech activity detector that continuously monitors signal characteristics and adjusts system parameters in real-time. The residual echo reduction circuit dynamically modifies its processing based on detected speech activity, allowing the system to adapt to changing acoustic conditions while maintaining reliable echo suppression performance.
3Object-generated harmful factors
If aggressive echo suppression is applied, then echo reduction improves, but speech quality and communication clarity deteriorate
Solution Approach 1:
The patent applies local quality by treating different frequency components and signal segments differently through the filter bank. Each sub-band is processed independently with appropriate echo suppression strength, and the speech activity detector applies selective processing only where needed. This localized approach reduces echoes effectively while preserving speech quality and avoiding unnecessary distortion of legitimate audio content.
Data Source
AI summary
A system for reducing an echo and/or a residual echo in a microphone output signal includes an echo compensation filter configured to receive audio input signals and generate an estimated echo signal. A speech activity detector is configured to detect speech of a local speaker, and a combining circuit is configured to generate an echo compensated signal by subtracting the estimated echo signal from the microphone output signal. A residual echo reduction circuit is configured to suppress the residual echo in the echo compensated signal based on the detected speech activity, and output an echo suppressed output signal. The echo reduction system may reduce local background noise and residual echoes in a microphone output signal so that local speech may be transmitted free from undesirable signals.