Concentric Polygon Microphone Arrays for Sound Direction Detection
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Solution Overview
Problem
Existing sound source direction determination devices face challenges in achieving high directivity while suppressing the occurrence of grating lobes without increasing the number of microphones, as narrowing the microphone spacing to prevent grating lobes reduces aperture and vice versa.
Innovation Solution
An array sensor with microphones arranged at the vertices of two or more concyclic polygons on the same plane, sharing the same center and arranged non-rotationally symmetrically, combined with a camera for superimposing sound pressure maps on captured images, to determine sound source direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If microphone spacing is increased to improve directivity, then aperture increases and directivity improves, but grating lobes occur causing misdetermination
Solution Approach 1:
The patent applies asymmetry by arranging microphones in non-rotationally symmetric patterns (e.g., irregular polygons, asymmetric distributions) rather than symmetric arrangements. This asymmetric configuration disrupts the spatial regularity that causes grating lobes, allowing larger microphone spacing while maintaining reliability and suppressing false signals.
Solution Approach 2:
The patent transitions from one-dimensional linear arrays to two-dimensional planar arrangements with varied geometries (polygons, irregular patterns). This dimensional change enables larger apertures while maintaining control over grating lobe occurrence through strategic positioning in the plane, resolving the contradiction between aperture size and grating lobe suppression.
2Reliability
If microphone spacing is decreased to suppress grating lobes, then grating lobe occurrence is reduced, but aperture becomes small and directivity cannot be secured
Solution Approach 1:
By using non-rotationally symmetric arrangements, the patent achieves grating lobe suppression without requiring small spacing. The asymmetric pattern prevents the regular phase differences that cause grating lobes, allowing larger spacing while maintaining both reliability and directivity.
Solution Approach 2:
The two-dimensional planar arrangements with varied geometries enable the system to achieve both large aperture and grating lobe suppression simultaneously. The spatial distribution in the plane provides degrees of freedom that allow optimizing both directivity and grating lobe control without the trade-off imposed by one-dimensional arrangements.
3Measurement precision
If number of microphones is increased to improve directivity, then directivity improves, but device complexity and cost increase
Solution Approach 1:
The non-rotationally symmetric arrangements optimize the spatial distribution of microphones, achieving high directivity with fewer elements. The asymmetric positioning maximizes the information content from each microphone, reducing the total number needed compared to conventional symmetric arrangements.
Solution Approach 2:
The two-dimensional planar configurations with varied geometries improve directivity more efficiently than one-dimensional arrays, achieving the same or better directivity performance with fewer microphones. This reduces device complexity and cost while maintaining measurement precision.
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 device enhances directivity and suppresses grating lobes effectively, allowing accurate sound source positioning with a reduced number of microphones.
Implementation Method 1
an array sensor including a plurality of microphones that measures a sound wave
Data Source
AI summary
A device for determining sound source direction includes an array sensor including a plurality of microphones that measures a sound wave, and a processor for calculating a sound pressure in each direction based on sound pressure information of the sound wave obtained by the array sensor and for determining a direction in which the sound pressure is maximum as a direction of sound wave arrival. The plurality of microphones is provided at vertices of two or more concyclic polygons that are on a same plane and that have a same center and are arranged so as to be non-rotationally symmetric as a whole array sensor.