Broadside Microphone Array Noise Suppression via Signal Subtraction
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Solution Overview
Problem
Existing communication and voice recognition systems face challenges in effectively suppressing noise, particularly non-stationary noise, in noisy environments, as conventional single microphone techniques distort speech at low SNR and array microphone techniques increase noise due to multiple microphones.
Innovation Solution
A broadside small array microphone beamforming unit is designed with two omni-directional microphones forming a reference and main channel, using delay units, substrators, and adaptive filters to adjust beam direction and reduce internal noise, enhancing noise suppression and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If array microphone techniques are used to suppress non-stationary noise, then noise suppression capability is improved, but internal noise increases due to multiple microphones
Solution Approach 1:
The patent extracts and removes the harmful internal noise components generated by multiple microphones in the array. The noise reduction unit specifically targets and extracts internal noise from the combined signal of multiple microphones, separating it from the useful speech signal to achieve noise suppression without the penalty of increased internal noise.
Solution Approach 2:
The patent introduces a noise reduction unit as an intermediary component between the microphone array and the speech processing system. This intermediary unit processes the combined signal from multiple microphones, reducing internal noise while preserving the speech signal and non-stationary noise suppression capabilities.
2Object-affected harmful factors
If conventional single microphone spectral subtraction is used to reduce stationary noise, then stationary noise reduction is achieved, but speech signal distortion occurs at low SNR
Solution Approach 1:
The patent changes the processing parameters and approach by using array microphone techniques with multiple microphones instead of single microphone spectral subtraction. The noise reduction unit adjusts processing parameters to reduce stationary noise while maintaining speech signal integrity, avoiding the distortion problems that occur with conventional single microphone methods at low SNR.
3Object-affected harmful factors
If multiple microphones are placed at different locations to form a beam, then non-stationary noise suppression is improved, but device complexity increases
Solution Approach 1:
The patent makes the noise reduction unit multi-functional, enabling it to handle both stationary and non-stationary noise types. By integrating multiple noise reduction capabilities into a single unit that processes signals from the microphone array, the system achieves versatile noise suppression without proportionally increasing device complexity.
Data Source
AI summary
A broadside small array microphone beamforming unit comprises a first omni-directional microphone to generate a signal X1(t), a second omni-directional microphone to generate a signal X2(t), a first delay unit delaying the signal X1(t) to generate a signal X1(t−T), a second delay unit delaying the signal X2(t) to generate a signal X2(t−T), a first substrator subtracting the signal X1(t−T) from the signal X2(t) to generate a signal R(t)=X2(t)−X1(t−T), a second substrator subtracting the signal X2(t−T) from the signal X1(t) to generate a signal L(t)=X1(t)−X2(t−T), a third delay unit delaying the signal R(t) to generate a signal R′(t)=R(t−D), a gain function unit convoluting the signal L(t) with a gain function G(t) to generate a signal L′(t)=L(t)*G(t−i), and a substrator subtracting the signal L′(t) from the signal R′(t) to generate a signal B′(t)=R′(t)−L′(t).