Cylindrical Microphone Array for 3D Sound Capture With Fewer Sensors
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Solution Overview
Problem
Conventional surround sound systems face challenges in accurately reproducing three-dimensional sound fields due to the need for large numbers of microphones and loudspeakers, leading to spatial aliasing and inefficiencies in spherical harmonics decomposition, especially in 3D arrays, which are impractical and costly to implement.
Innovation Solution
A cylindrical microphone array with multiple line arrays around its circumference, each producing vertical beamformer responses, allows for efficient recording and reproduction of three-dimensional sound fields by generating cylindrical coefficients based on azimuthal decompositions and applying mode equalizers to reduce diffraction effects and improve spatial resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spherical microphone arrays are used to record 3D sound fields, then spatial resolution in all directions can be achieved, but the number of microphones and spherical harmonics required becomes excessively large
Solution Approach 1:
The patent divides the spherical microphone array into multiple cylindrical sub-arrays arranged vertically. Each cylindrical array records sound fields in its local coordinate system with fewer microphones, and the results are combined through coordinate transformation to reconstruct the complete 3D sound field, reducing the total microphone count while maintaining spatial resolution
Solution Approach 2:
The patent transforms the problem from spherical coordinates to cylindrical coordinates, exploiting the vertical arrangement of microphones to capture elevational information more efficiently. By organizing microphones in vertical cylindrical arrays rather than spherical distributions, the system achieves 3D sound field recording with reduced microphone requirements
2Adaptability or versatility
If spherical loudspeaker arrays are used to reproduce surround sound, then sound can be reproduced from all directions, but the system becomes complex and requires many loudspeakers to avoid spatial aliasing
Solution Approach 1:
The patent inverts the conventional approach by recording in cylindrical coordinates and reproducing through cylindrical loudspeaker arrays rather than using spherical arrays for both recording and reproduction. This inversion simplifies the reproduction system while maintaining the ability to reproduce 3D sound fields, as cylindrical arrays require fewer elements to achieve the same spatial coverage
Solution Approach 2:
The patent changes the coordinate system parameter from spherical to cylindrical, which fundamentally alters the mathematical description of sound fields. This parameter change enables more efficient reproduction with fewer loudspeakers by matching the recording coordinate system with the reproduction array geometry, avoiding the complexity of spherical harmonic synthesis
3Measurement precision
If high-order spherical harmonics are used to describe the sound field, then sufficient resolution is achieved, but the computational complexity and data processing requirements increase significantly
Solution Approach 1:
The patent changes the mathematical framework from spherical harmonics to cylindrical wave functions, which better suit the vertical array geometry. This dimensionality change in the coordinate system leads to simpler decomposition and reconstruction algorithms, reducing computational complexity while maintaining sound field description accuracy
Solution Approach 2:
The patent changes the basis functions from spherical harmonics to cylindrical wave functions, fundamentally altering the mathematical representation of the sound field. This parameter change in the decomposition method reduces the number of coefficients required and simplifies the transformation operations, lowering computational burden
Data Source
AI summary
Provided are methods, systems, and apparatuses for recording a three-dimensional (3D) sound field using a vertically-oriented cylindrical array with multiple circular arrays at different heights. The design of the cylindrical array is well-suited to providing a high-resolution in azimuth and a reduced resolution in elevation, and offers improved performance over existing 3D sound reproduction systems. The methods, systems, and apparatuses provide a larger vertical aperture than horizontal aperture, as opposed to a spherical array, which has the same aperture for all dimensions, and further provides an alternative format to mixed-order spherical decomposition.