Acoustic Echo Cancellation with Near-End Pitch Preservation
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Solution Overview
Problem
Existing acoustic echo cancellation devices introduce audible signal distortions when the far-end echo is much louder than the near-end signal, particularly in modern mobile devices where the loudspeaker and microphone are closely positioned, leading to insufficient echo suppression.
Innovation Solution
Incorporating a near-end pitch estimation unit to estimate the pitch of the near-end signal and control the post-processor to preserve harmonics of the estimated pitch, and an echo pitch estimation unit to provide a more accurate estimate, ensuring that the post-processor selectively attenuates only the echo components while maintaining the near-end signal's harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the post-processor selectively attenuates frequencies with significant residual far-end echo, then echo suppression is improved, but the near-end signal may be accidentally suppressed causing audible signal distortions
Solution Approach 1:
The patent employs a feedback mechanism by estimating the pitch of the near-end signal and using this information to control the post-processor. The pitch estimation unit continuously monitors the near-end signal characteristics, and this feedback is used to adjust the attenuation parameters of the post-processor, ensuring that frequencies corresponding to the near-end signal pitch and its harmonics are preserved while still attenuating echo frequencies.
Solution Approach 2:
The patent changes the parameters of the post-processor based on the estimated near-end signal pitch. By dynamically adjusting the attenuation characteristics of the post-processor according to the detected pitch parameters, the system adapts to different speech conditions and prevents accidental suppression of the near-end signal while maintaining effective echo suppression.
2Volume of moving object
If the loudspeaker and microphone are positioned close together to reduce device size, then device compactness is improved, but echo loudness increases causing insufficient echo suppression
Solution Approach 1:
The patent addresses the increased echo loudness caused by close positioning by dynamically changing the processing parameters of the post-processor. The system adapts its attenuation characteristics based on the actual echo and near-end signal conditions, allowing effective echo suppression even when the devices are positioned close together, thus maintaining device compactness while compensating for the increased echo problem.
Data Source
AI summary
An acoustic echo cancellation device (1) for canceling an echo in a microphone signal (z) in response to a far-end signal (x) comprises: an adaptive filter unit (10) arranged for filtering the far-end signal (x) so as to produce an echo cancellation signal (y), —a combination unit (12) arranged for combining the echo cancellation signal (y) with the microphone signal (z) so as to produce a residual signal (r), and a post-processor unit (13) arranged for substantially removing any remaining echoes from the residual signal. In accordance with the invention, the device further comprises: —a near-end pitch estimation unit (18) arranged for estimating the pitch of any near-end signal (s) contained in the microphone signal (z) and for controlling the post-processor unit (13) in dependence of the estimated pitch such that harmonics of the estimated pitch may be substantially preserved. The control unit may further be arranged for controlling the post-processor unit (13) in dependence of the estimated pitch of the residual signal in addition to the estimated pitch of the residual signal.