Orthogonal Microphone Array Low-Frequency SN Ratio
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Solution Overview
Problem
Existing microphone array systems with a small number of microphones face challenges in maintaining a sufficient Signal-to-Noise (SN) ratio, particularly in the low frequency band.
Innovation Solution
The microphone array system employs a configuration of microphones disposed along orthogonal axes with specific interval distances, utilizing beamforming processors to combine audio signals and project microphones to create virtual microphone positions, resulting in improved SN ratio through optimized microphone placement and signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a small number of microphones are used, then device complexity is reduced, but SN ratio in low frequency band deteriorates
Solution Approach 1:
The patent transitions from a single-axis linear array to a two-dimensional orthogonal array configuration. By arranging microphones along both the first axis (X-direction) and second axis (Y-direction), the system creates a planar aperture that enhances low-frequency response without increasing the number of microphones. This dimensional expansion allows the small microphone array to achieve effective spatial filtering and noise rejection comparable to larger single-axis arrays.
Solution Approach 2:
The patent employs asymmetric spacing between microphones on the first axis versus the second axis. Specifically, the interval between adjacent microphones on the first axis is set to be larger than the interval on the second axis. This asymmetric configuration optimizes the array's spatial frequency response, allowing it to maintain good SN ratio in low frequency bands while keeping the total microphone count small. The asymmetric layout creates favorable interference patterns that enhance noise rejection.
2Volume of moving object
If microphones are spaced closely to reduce device size, then compactness is improved, but low frequency response deteriorates
Solution Approach 1:
By expanding the array into two dimensions with orthogonal axes, the system achieves an effective aperture area that is larger than a compact single-axis linear array of the same physical footprint. The two-dimensional arrangement allows microphones to be distributed over a larger spatial extent in the planar direction, improving low-frequency response while maintaining compactness in the depth direction.
Solution Approach 2:
The patent optimizes the spacing parameters between microphones on each axis to balance compactness and low-frequency response. By carefully selecting the interval distances on the first and second axes, the system achieves a compact device size while maintaining sufficient spatial separation to capture low-frequency acoustic variations. The asymmetric parameter selection allows one axis to be more compact while the other provides the necessary baseline for low-frequency response.
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 configuration enhances the SN ratio in the low frequency band, reducing the influence of interior noise, reverberation, and echo, while allowing for effective beamforming and voice separation, even with a small number of microphones.
Implementation Method 1
a beamforming processor that performs beamforming by filtering and combining audio signals from the plurality of first microphones and the plurality of second microphones
Data Source
AI summary
A microphone array system includes first microphones disposed along a first axis, second microphones disposed at equal intervals of a first distance from the first axis along a second axis orthogonal to the first axis, a beamforming processor that performs beamforming by filtering and combining audio signals from microphones, and, when the second microphones are projected onto the first axis, the first microphones and projected second microphones are disposed at equal intervals of a second distance, a distance between two microphones disposed at opposite ends, among the first microphones and the projected second microphones arranged along the first axis when the second microphones are projected onto the first axis, is larger than a distance between two microphones disposed at opposite ends, among the first microphones and the projected second microphones arranged along the second axis when the first microphones are projected onto the second axis.