Non-uniform Microphone Array Beamforming for Spatial Aliasing
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Solution Overview
Problem
Conventional microphone arrays with a fixed configuration struggle to achieve desired beam patterns across a wide range of frequencies, particularly experiencing side lobes and grating lobes, which lead to unwanted sound acquisition and increased manufacturing costs due to the need for a large number of microphones.
Innovation Solution
A non-uniform microphone array configuration with at least three microphones, a frequency conversion unit, a band division and merging unit, and a two-channel beamforming unit, which transforms acoustic signals into the frequency domain, divides frequencies into bands based on microphone intervals, and performs beamforming to reduce noise from unwanted directions, minimizing redundant components and avoiding spatial aliasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a larger microphone array is used to obtain desirable beam patterns for lower frequency bands, then the beam pattern quality for lower frequencies is improved, but side lobes or grating lobes occur in higher frequency bands causing sound in unwanted directions to be acquired
Solution Approach 1:
The patent divides the frequency spectrum into multiple frequency bands and processes each band separately using different beamforming techniques. This segmentation allows the system to use appropriate microphone subsets for each frequency range, avoiding the harmful effects of using a single large array configuration for all frequencies.
Solution Approach 2:
The system dynamically selects and switches between different beamforming methods (full array beamforming for low frequencies, sub-array beamforming for high frequencies) based on the input signal's frequency characteristics. This dynamic adaptation eliminates the static limitations of fixed beamforming approaches.
2Device complexity
If a fixed beamforming technique is used that is independent of input signal characteristics, then the system complexity is reduced, but the beam pattern becomes omni-directional when a smaller microphone array is used
Solution Approach 1:
The system implements dynamic beamforming that automatically adapts to different frequency bands and signal characteristics. By switching between full array and sub-array configurations based on frequency content, the system maintains directional performance without requiring excessive complexity in a single fixed algorithm.
Solution Approach 2:
The patent changes operational parameters (microphone array configuration, beamforming weights) based on frequency band detection. This parameter adaptation allows the system to maintain effective beam patterns across varying conditions without requiring a single complex fixed solution.
3Manufacturing precision
If at least ten microphones are used to form a desired beam pattern, then the beam pattern quality is improved, but the manufacturing cost and application complexity of the microphone array increase
Solution Approach 1:
The patent segments the microphone array into multiple sub-arrays that can be independently configured for different frequency bands. This allows achieving high-quality beam patterns using fewer total microphones by optimally utilizing subsets of the array for specific frequency ranges, rather than requiring all microphones to function uniformly across all frequencies.
Solution Approach 2:
Different portions of the microphone array (sub-arrays) are optimized for different frequency ranges, with each sub-array configured to provide optimal performance for its designated frequency band. This local optimization achieves high beam pattern quality without requiring a uniformly high-count array across all frequencies.
Data Source
AI summary
An audio quality enhancing apparatus and method is provided in which a microphone array has a non-uniform configuration and thus a beam pattern of a desired direction is obtained in a wide range of frequencies including higher frequency bands and lower frequency bands even when the microphone array is relatively small. The audio quality enhancing apparatus includes at least three microphones which are disposed in a non-uniform configuration, a frequency conversion unit configured to transform acoustic signals input from the at least three microphones to acoustic signals of frequency domain; a band division and merging unit configured to divide frequencies of the transformed acoustic signals into bands based on intervals between the at least three microphones and to merge the acoustic signals in the frequency domain into signals of two channels based on the divided frequency bands; and a two channel beamforming unit configured to reduce noise of signals including input from a direction other than the direction of a target sound by performing beamforming on the signals of the two channels and to output the noise-reduced signals.