Microphone Noise Suppression via Adaptive Beamforming
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Solution Overview
Problem
Existing audio processing systems face a trade-off between improving signal quality and preserving signal coherence, particularly in isolating desired speech from noise sources, which affects the effectiveness of noise cancellation and echo suppression in electronic devices.
Innovation Solution
A noise-suppression system that employs a beam selector to identify the most likely direction of a noise source, using an adaptive filter with a parallel filter to differentiate pre-wakeword noise from post-wakeword speech, and adjusts the noise estimate based on diffuseness and signal quality to maintain signal coherence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If noise cancellation processing is applied to improve signal quality, then noise suppression effectiveness is improved, but signal coherence is deteriorated
Solution Approach 1:
The system performs preliminary beam selection to identify the direction of noise sources before applying noise cancellation processing. By pre-identifying noise directions through beamformed audio signals, the system can selectively apply cancellation only to specific directional components, preserving coherence of non-noise signals while effectively suppressing identified noise sources.
Solution Approach 2:
The audio signal is segmented into different directional components through beamforming, with separate processing applied to each direction. The beam selector divides the audio space into multiple beams, allowing independent noise cancellation processing for each directional segment, thereby maintaining coherence within each segment while achieving overall noise suppression.
2Measurement precision
If beam switching is performed frequently to track noise sources, then noise tracking accuracy is improved, but processing stability is deteriorated
Solution Approach 1:
The beam selection process is made dynamic and adaptive, allowing the system to switch between different beam configurations based on real-time noise characteristics. The beam selector continuously evaluates beamformed signals and adjusts beam selection to track moving noise sources, providing dynamic adaptation while maintaining processing stability through controlled transition criteria.
3Object-affected harmful factors
If aggressive noise filtering is applied to remove noise, then signal quality is improved, but signal distortion is increased
Solution Approach 1:
Different processing qualities are applied to different directional components of the audio signal. Noise-containing directional beams receive aggressive filtering, while clean directional beams are preserved with minimal processing. This local differentiation of processing intensity allows aggressive noise removal where needed while protecting clean signal portions from distortion.
Data Source
AI summary
Techniques for improving microphone noise suppression are provided. A system for noise-suppression may include a beam selector component that applies logic to select a beam most likely corresponding to a direction of a noise source and keeps the beam selection steady rather than switching the beam too often to avoid processing complications. The selected beam may be used as a reference in an adaptive filter which outputs a noise estimate. The noise estimate and raw microphone data may be used to adapt the adaptive filter. A parallel filter which adapts after a time delay may be applied to the reference in order to prevent interference. An attenuation factor may be used to scale the noise estimate based on noise diffuseness, signal quality, and/or a gain limit. The scaled noise estimate may be subtracted from microphone input data to produce output audio data with improved signal quality and maintained signal coherence.