Adaptive Acoustic Echo Cancellation for Changing Audio Paths
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Solution Overview
Problem
Current audio-conference communication systems face challenges in effectively reducing acoustic echoes due to varying acoustic paths between loudspeakers and microphones, leading to interruptions in conversations with brief periods of silence.
Innovation Solution
The method involves computing a control state based on signals transmitted between locations and determining an approximate acoustic echo to subtract from the digital signal, adjusting for gain and transmitting an output signal that minimizes residual echoes, using adaptive filtering and discrete Fourier transforms to efficiently process audio signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stand alone adaptive filters are used to reduce acoustic echoes, then the system can provide basic echo cancellation, but the filters fail to account for or are slow to adapt to the widely varying acoustic path between loudspeaker and microphone, causing interruptions in conversations with brief periods of silence
Solution Approach 1:
The patent implements dynamic adaptation by continuously updating the acoustic path model based on real-time signal analysis. The system transitions from static filter coefficients to dynamically adjusted parameters that track changes in the acoustic environment, allowing the echo canceller to adapt rapidly to varying conditions without causing conversation interruptions
Solution Approach 2:
The system employs feedback mechanisms where the output of the echo canceller is analyzed and used to adjust the filter parameters. By monitoring the residual echo and adapting the acoustic path model based on this feedback, the system achieves reliable echo cancellation while maintaining adaptability to changing acoustic conditions
2Object-generated harmful factors
If filtering systems employ adaptive filters to reduce acoustic echoes, then echo cancellation is provided, but the filters are slow to adapt to changing conditions at audio-signal-receiving locations, resulting in transmission interruptions
Solution Approach 1:
The system performs preliminary characterization of the acoustic path during periods when echo is present, building a model before it is needed for cancellation. This advance preparation allows the system to rapidly respond when acoustic conditions change, eliminating the delay associated with real-time adaptation
Solution Approach 2:
The patent utilizes parameter changes in the adaptive filter coefficients and acoustic path model to enable fast adaptation. By adjusting key parameters such as filter order, step size, and model complexity based on detected acoustic conditions, the system achieves rapid convergence without sacrificing echo cancellation effectiveness
Data Source
AI summary
Various embodiments of the present invention are directed to methods and systems that reduce acoustic echoes in audio signals in accordance with changing conditions at first and second locations that are linked together in a communication system. In one embodiment of the present invention, a first digital signal encoding sounds produced at the first location is output from the first location, and a second digital signal encoding an acoustic echo and sounds produced at the second location is output from the second location. The method computes a control state that depends on the signals transmitted between the first and the second locations and computes an approximate acoustic echo based on the control state.