Far Field Sound Capturing With Echo Cancellation And Beamforming
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Solution Overview
Problem
Far field sound capturing systems face challenges in noise reduction due to the low signal-to-noise ratio when the desired sound source is distant, as existing noise reduction methods like directional beamforming, spectral subtraction, and pitch-based speech enhancement are inadequate in separating desired signals from interfering noise, especially when they occupy the same temporal frequency band.
Innovation Solution
A system and method utilizing multiple microphones, a multi-channel acoustic echo canceller, and a beamformer to detect and separate desired-source and undesired-source beam signals, employing beamsteering and adaptive interference cancellation to enhance the signal-to-noise ratio by suppressing noise while preserving desired signals, using techniques such as generalized sidelobe cancellation and adaptive digital filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the distance between sound source and far field microphone is increased, then the coverage area is improved, but the signal-to-noise ratio deteriorates
Solution Approach 1:
The patent segments the audio signal processing into multiple independent stages: directional beamforming to capture spatial information, spectral subtraction to remove noise components, and pitch-based speech enhancement to preserve desired speech. Each stage processes specific aspects of the signal independently, allowing the system to maintain coverage area while improving signal-to-noise ratio through cumulative effect of multiple processing steps.
2Device complexity
If temporal filtering is used to separate desired signal from interference, then the signal separation is simplified, but it becomes ineffective when desired signal and interferers occupy the same temporal frequency band
Solution Approach 1:
The patent transitions from relying solely on temporal frequency domain filtering to incorporating spatial dimension information through directional beamforming. By adding the spatial dimension (direction of arrival) as an additional separation criterion, the system can effectively distinguish desired speech from interference even when they occupy the same temporal frequency band, thus improving reliability without excessive complexity increase.
3Measurement precision
If noise reduction techniques are applied to improve signal-to-noise ratio, then the desired signal quality is improved, but the complexity of the noise reduction system increases
Solution Approach 1:
The patent employs multiple noise reduction techniques that operate on different signal parameters: spectral subtraction modifies the frequency spectrum by removing noise spectral components, while pitch-based speech enhancement operates on the temporal parameter by preserving pitch-periodic components. This multi-parameter approach improves signal-to-noise ratio effectively while distributing the computational complexity across different processing domains rather than concentrating it in a single complex system.
Data Source
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AI summary
A system method for far field sound capturing, the method includes picking up sound to provide M ≥ 2 microphone signals, echo cancelling processing the M microphone signals (and one or more reference signals) to provide M echo cancelled signals, and beamforming processing the M echo cancelled signals to provide B ≥ 1 beamformed signals.