3D Wave Field Acquisition Using Opposed Planar Sensor Arrays
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Solution Overview
Problem
Current methods for acquiring 3D wave field signals, such as spherical and planar microphone arrays, face challenges including high costs, complexity, and reduced accuracy due to scattering and vibration issues, while existing 2D arrays are limited to 2D representations and less portable.
Innovation Solution
A signal acquisition device with two 2D arrays of omnidirectional sensors on opposite sides of a rigid plate allows for accurate determination of even and odd modes of wave fields, reducing computational costs and scattering effects, enabling the construction of a 3D wave field representation through linear and time-invariant modeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a spherical array of pressure microphones is used to capture 3D wave field signals, then the ability to transform into spherical harmonic decomposition is improved, but the cost and complexity increase asymptotically with the square of the frequency ratio
Solution Approach 1:
The patent transitions from spherical 3D geometry to planar 2D geometry for microphone array arrangement. By placing microphones on a flat surface rather than distributing them spherically in three-dimensional space, the system achieves 3D wave field representation with reduced complexity. This dimensional simplification allows standard PCB production techniques to be used while maintaining the capability to capture spherical harmonic decomposition up to certain orders.
Solution Approach 2:
The patent uses pairs of pressure sensors in close proximity to each other as first-order sensors, creating a simplified copy of the spherical array functionality. Instead of requiring numerous individually positioned microphones on a sphere, the planar arrangement uses sensor pairs that collectively provide the necessary spatial information through differential measurements, reducing the total number of sensors needed.
2Duration of action of moving object
If first-order sensors are used in a planar 2D array to capture odd components of spherical harmonic decomposition, then the frequency range is improved, but the low-frequency limit is governed by the distance between sensors within each pair
Solution Approach 1:
The patent introduces a rigid plate as an intermediary element between the sound field and the sensors. The plate serves as a scattering surface that converts incident sound waves into vibrations, which are then detected by pressure sensors mounted on the plate. This intermediary mechanism allows the system to capture both even and odd spherical harmonic components without being constrained by the close spacing requirements of direct first-order sensor pairs.
Solution Approach 2:
The patent replaces the acoustic measurement approach with a mechanical coupling approach. Instead of relying on pressure sensors to directly detect acoustic pressure gradients (which requires very close spacing), the system uses the rigid plate to mechanically couple the sound field to the sensors. The plate's vibrations in response to incident sound provide the necessary spatial information, substituting direct acoustic measurement with mechanical vibration detection.
3Ease of manufacture
If sensors, wiring and electronic components are placed on a planar array, then the manufacturing ease is improved, but the scattering of wave field increases reducing accuracy
Solution Approach 1:
The rigid plate serves as an acoustic intermediary that separates the sound field interaction from the electronic components. The plate's large surface area relative to the wavelength causes it to scatter incident sound waves, but this scattering is predictable and can be compensated for in the signal processing. The sensors are mounted on the plate rather than being exposed directly to the sound field, allowing standard PCB mounting techniques to be used while the plate handles the acoustic interaction.
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 approach effectively acquires and reconstructs 3D wave field signals with reduced computational costs and increased accuracy, facilitating applications like active noise cancellation, beamforming, and sound recording, while being more portable and robust compared to traditional methods.
Implementation Method 1
the plate scatters the wave field to some extent, thereby reducing the accuracy of the constructed wave field representation
Implementation Method 2
the plate vibrates in response to the incident wave field and generates vibration-induced pressure signals
Data Source
AI summary
A Signal acquisition device is described for acquiring three-dimensional wave field signals. The signal acquisition device comprises an acoustically reflective plate (PLT) comprising two planar sides facing oppositely and a two-dimensional array of inherently omnidirectional sensors (TSS) arranged on one of the two sides, characterized in that the sound recording device comprises another two-dimensional array of inherently omnidirectional sensors (BSS) arranged on the other of the two sides.