Spherical Microphone Array with Truncated Icosahedron Diffraction
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Solution Overview
Problem
Spherical microphone arrays face limitations in accurately describing sound fields due to low-frequency noise amplification and high-frequency spatial aliasing, restricting their usable frequency range and requiring high sensor density, which increases costs.
Innovation Solution
A spherical microphone array design featuring a sound-diffracting structure with a truncated icosahedron pattern and cavities with omnidirectional microphones, where microphones are arranged to form both a spatial low-pass filter and focusing element, reducing spatial aliasing and enhancing directivity by using a combination of inner and outer oval lines for microphone placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If microphones are densely distributed over the sphere surface, then spatial aliasing is reduced, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent introduces a sound-diffracting structure with specific cavities as an intermediary between the incoming sound waves and the microphones. This structure pre-processes the acoustic field by creating controlled diffraction patterns and focusing effects, which allows the microphones to capture spatial information more efficiently. The cavities act as acoustic lenses that concentrate and direct sound energy, enabling accurate spatial sampling with fewer microphones.
Solution Approach 2:
The patent changes the geometric parameters of the microphone array by using non-uniform distribution patterns (oval lines at different radii) instead of uniform spherical distribution. By varying the radial position and angular distribution of microphones according to specific geometric patterns, the array achieves optimal spatial sampling characteristics that reduce aliasing while using fewer sensors.
2Measurement precision
If microphone directivity is improved at low frequencies, then noise amplification is reduced, but the array's frequency response range is limited
Solution Approach 1:
The patent transitions from considering only angular distribution to incorporating radial dimension in the microphone placement strategy. By positioning microphones at different radii from the sphere center along specific oval trajectories, the system creates a three-dimensional sampling pattern that enhances low-frequency capture capability while preserving high-frequency response through the combined geometric configuration.
Solution Approach 2:
The patent employs curved oval trajectories for microphone placement instead of straight lines or simple circular patterns. These curved paths are specifically designed to optimize the spatial distribution of microphones in three-dimensional space, creating favorable interference patterns that enhance directivity at low frequencies while maintaining broad frequency coverage through the curved geometric configuration.
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 design extends the upper frequency limit and reduces noise, improving the array's ability to accurately capture sound fields without significant artifacts, while maintaining cost-effectiveness by optimizing microphone placement and directivity.
Implementation Method 1
A spherical microphone array includes a sound-diffracting structure that has a closed three-dimensional shape of at least one non-regular, regular or semi-regular convex polyhedron
Implementation Method 2
at least one cavity disposed in the sound-diffracting structure, the at least one cavity having an aperture, an end, and a center line between the end of the cavity and the center of aperture
Data Source
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AI summary
A spherical microphone array that includes a sound-diffracting structure having a closed three-dimensional shape of at least one non-regular, regular or semi-regular convex polyhedron with congruent faces of regular or non-regular polygons and at least two omnidirectional microphones disposed in or on the sound-diffracting structure on an oval line whose center is disposed on a center line that subtends the center of one of the faces of the regular polygons.