Near-End Audio Echo Detection and Suppression via Cross-Correlation
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Solution Overview
Problem
Existing communication systems during conferences often suffer from acoustic coupling, where near-end audio is returned as echo due to the absence of a working echo canceller at the far-end unit, causing distractions for the near-end participant.
Innovation Solution
The near-end unit detects and suppresses returned audio by determining energy outputs for separate bands of near-end and far-end audio, using cross-correlation to estimate time delays and implement muting or reduction of far-end audio output at the loudspeaker to prevent echo.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If near-end echo cancellation is used to reduce acoustic coupling at the near-end unit, then the far-end participant does not hear his own voice returned, but the near-end participant still hears near-end audio returned from the far-end as echo
Solution Approach 1:
The system uses feedback by monitoring the far-end audio signal and comparing it with the near-end audio signal after a time delay. When a correlation is detected indicating returned audio, the system activates suppression mechanisms to reduce or mute the far-end audio output, thereby eliminating the echo feedback loop.
Solution Approach 2:
An intermediary echo detection and suppression module is introduced between the audio decoder and loudspeaker. This module analyzes the audio signals, detects returned echo through cross-correlation analysis, and controls the loudspeaker output accordingly, acting as a mediator to prevent echo without affecting the main audio playback function.
2Object-affected harmful factors
If the far-end unit lacks a working acoustic echo canceller, then acoustic coupling occurs and returns near-end audio to the near-end participant, but adding echo cancellation at the far-end increases device complexity
Solution Approach 1:
Instead of implementing echo cancellation at the far-end unit (where the acoustic coupling originates), the system inverts the approach by placing the echo detection and suppression functionality at the near-end unit. This allows the near-end participant to control and suppress returned echo without requiring modifications or increased complexity at the far-end unit.
3Measurement precision
If cross-correlation analysis is performed over a wide time delay range to accurately detect returned audio, then detection precision improves, but processing time and computational complexity increase
Solution Approach 1:
The time delay range is segmented into multiple discrete delay taps or time bins. Instead of performing a continuous cross-correlation over the entire time range, the system divides the search space into segments and processes them individually, allowing for efficient detection while reducing overall computational burden and processing time.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively reduces the occurrence of near-end audio being returned as echo, improving the conferencing experience by minimizing distractions and handling varying time delays and distortions introduced by the far-end unit.
Implementation Method 1
The comparison can use a cross-correlation to find an estimated time delay used for further analysis of the near and far-end energies.
Implementation Method 2
Due to the proximity of the loudspeaker 20 and microphone 40, acoustic coupling (indicated by arrow 11) may occur in which far-end audio output by the loudspeaker 20 is picked up by the microphone 40
Data Source
AI summary
Audio from a near-end that has been acoustically coupled at the far-end and returned to the near-end unit is detected and suppressed at the near-end of a conference. First and second energy outputs for separate bands are determined for the near-end audio being sent from the near-end unit and for the far-end audio being received at the near-end unit. The near-end unit compares the first and second energy outputs to one another for each of the bands over a time delay range and detects the return of the sent near-end audio in the received far-end audio based on the comparison. The comparison can use a cross-correlation to find an estimated time delay used for further analysis of the near and far-end energies. The near-end unit suppresses any detected return by muting or reducing what far-end audio is output at its loudspeaker.