3D Microphone Array Spatial Filtering
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Solution Overview
Problem
Conventional microphone systems face challenges in distinguishing sound sources in three-dimensional space due to mirror issues, where they can differentiate between right and left but struggle with front and back, or upper and lower directions, limiting their directionality and accuracy.
Innovation Solution
A microphone system comprising a microphone array and a processing unit that performs spatial filtering using a trained model based on target beam areas and microphone coordinates, enhancing the ability to distinguish sound source locations by adjusting the geometry and incorporating spacers to create energy discrepancies, thereby improving directionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a two-microphone array is used for beamforming, then the system can distinguish right from left directions, but it cannot distinguish front from back or upper from lower due to mirror symmetry
Solution Approach 1:
The patent transitions from a two-microphone planar array to a three-dimensional microphone array with at least four microphones positioned in 3D space. This dimensional expansion breaks the mirror symmetry that plagues 2D arrays, enabling the system to distinguish front from back and upper from lower directions by exploiting time delay differences across multiple spatial dimensions.
Solution Approach 2:
The patent intentionally introduces asymmetric microphone positioning in three-dimensional space, where microphones are placed at non-symmetric coordinates relative to the sound source. This asymmetric geometry creates unique time delay patterns for different spatial directions, allowing the beamforming algorithm to resolve directional ambiguities that plague symmetric two-microphone configurations.
2Device complexity
If microphones are positioned symmetrically about an axis, then the system simplifies calculation, but it creates mirror issues where front and back directions cannot be distinguished
Solution Approach 1:
By moving from 2D symmetric positioning to 3D asymmetric positioning, the patent adds spatial dimensionality that provides additional independent time delay measurements. This enables the system to resolve directional ambiguities while maintaining manageable computational complexity through established beamforming algorithms adapted for 3D arrays.
3Device complexity
If only time delay information is used for sound source localization, then the system is computationally simple, but it cannot determine distance or resolve mirror ambiguities
Solution Approach 1:
The patent leverages the additional spatial dimension provided by 3D microphone array positioning to extract multiple independent time delay parameters. By processing time delays from multiple microphone pairs in three-dimensional space, the system can simultaneously determine both direction and distance to sound sources, resolving the limitations of simple two-microphone time delay estimation.
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
The system effectively increases the dimensionality for distinguishing sound sources, allowing for precise localization in three-dimensional space, enhancing the capability to differentiate between sound sources in various directions and improving the overall directionality and accuracy of sound source identification.
Implementation Method 1
The microphone array comprises Q microphones that detect sound to generate Q audio signals
Implementation Method 2
Beamforming techniques use the time differences between channels that results from the spatial diversity of the microphones to enhance the reception of signals from desired directions and to suppress or eliminate the undesired signals coming from other directions
Data Source
AI summary
A microphone system is disclosed, comprising: a microphone array and a processing unit. The microphone array comprises Q microphones that detect sound and generate Q audio signals. The processing unit is configured to perform operations comprising: spatial filtering over the Q audio signals using a trained model based on at least one target beam area (TBA) and coordinates of the Q microphones to generate a beamformed output signal originated from ω target sound source inside the at least one TBA, where ω>=0. Each TBA is defined by r time delay ranges for r combinations of two microphones out of the Q microphones, where Q>=3 and r>=1. A dimension of a first number for locations of all sound sources able to be distinguished by the processing unit increases as a dimension of a second number for a geometry formed by the Q microphones increases.