Acoustic Echo Cancellation Using Internal Loudspeaker Microphone
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Solution Overview
Problem
Conventional acoustic echo cancellation techniques are ineffective in suppressing the nonlinear component of acoustic echo signals, while successfully canceling the linear component, especially when using small loudspeakers that produce a larger nonlinear echo component.
Innovation Solution
The method involves placing a low sensitivity microphone inside the loudspeaker enclosure to capture the sound pressure level output as a reference signal for acoustic echo cancellation, allowing for effective attenuation of the nonlinear echo component by using this reference signal for subtractive cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional AEC techniques are used, then linear echo cancellation is achieved, but nonlinear echo component is not suppressed
Solution Approach 1:
The patent segments the echo signal into linear and nonlinear components, applying different processing approaches. The reference signal from the microphone inside the loudspeaker enclosure captures both components, allowing the AEC system to separately identify and cancel the nonlinear portion that conventional methods miss.
Solution Approach 2:
The patent introduces an intermediary reference signal obtained by capturing the loudspeaker output directly with an internal microphone. This reference signal serves as a mediator that provides accurate information about both linear and nonlinear echo components, enabling the AEC algorithm to suppress the nonlinear portion effectively.
2Volume of moving object
If a small loudspeaker is used, then device size is reduced, but nonlinear echo component increases
Solution Approach 1:
The patent implements a feedback mechanism where a microphone inside the loudspeaker enclosure continuously monitors the actual output signal, including nonlinear distortions. This feedback loop provides real-time information about the nonlinear components, allowing the AEC system to adapt and cancel them effectively despite the small loudspeaker size.
Solution Approach 2:
The patent converts the harmful nonlinear distortion generated by the small loudspeaker into a useful signal. By capturing the nonlinear component with the internal microphone and including it in the reference signal, the system transforms what was previously a harmful artifact into information that enables effective echo cancellation.
3Quantity of substance
If reference signal is captured outside enclosure, then near end signal is included, but echo reference accuracy decreases
Solution Approach 1:
The patent extracts the reference signal capture location from the external environment and places it inside the loudspeaker enclosure. This extraction removes contamination from near-end signals and ambient noise, isolating the reference signal to contain only the loudspeaker output including its nonlinear components.
Solution Approach 2:
The patent changes the spatial dimension of reference signal capture from outside to inside the loudspeaker enclosure. This dimensional change fundamentally alters the signal composition, creating a reference that accurately represents the actual acoustic output including nonlinear distortions, which cannot be achieved from external capture.
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
This approach effectively cancels the nonlinear echo component while preserving the linear echo cancellation, improving overall echo suppression and reducing latency in communication systems.
Implementation Method 1
use a microphone inside the loudspeaker cavity to capture the sound pressure level (SPL) output of the loudspeaker
Implementation Method 2
The loudspeaker is operable to play back a far end signal
Implementation Method 3
The method enables attenuating, using the reference signal, the far end component in the electrical acoustic signal
Data Source
AI summary
Systems and methods for acoustic echo cancellation are provided. An example method includes receiving a reference signal. The reference signal represents at least one sound captured inside an enclosure of a loudspeaker. The loudspeaker is operable to play back a far end signal. The method also includes receiving an acoustic signal. The acoustic signal represents at least one sound captured outside the enclosure of the loudspeaker. The acoustic signal includes at least a near end signal and the far end signal. The method enables attenuation, using the reference signal, the far end signal in the acoustic signal. The reference signal can be captured by a low sensitivity microphone placed inside the enclosure of the loudspeaker. The attenuation of the far end signal may include subtractive cancellation.