Spatial Encoding Microphone Array for Mobile Spatial Audio
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Solution Overview
Problem
Current technologies face challenges in accurately capturing and processing spatial sound fields on mobile devices due to limitations in microphone arrays and signal processing, particularly in measuring higher-order spatial derivatives of acoustic pressure fields, which results in noise amplification and reduced signal quality.
Innovation Solution
The use of multiple microphones arranged in specific configurations, such as tetrahedral and spherical arrays, combined with advanced signal processing techniques, to generate a basis set of signals for post-processing and playback of spatial audio, including the application of differential microphone arrays and diffraction filtering to enhance signal quality and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If higher-order spatial derivatives of acoustic pressure field are measured using conventional microphone arrays, then spatial audio recording accuracy is improved, but noise amplification increases and signal-to-noise ratio deteriorates
Solution Approach 1:
The patent segments the measurement task by using multiple microphones (at least four) arranged in specific geometric configurations (tetrahedral, spherical, or planar arrays) to separately capture acoustic pressure and its spatial derivatives. Each microphone measures local pressure, and through signal processing, the system reconstructs higher-order spatial derivatives without directly differentiating noisy signals, thereby maintaining measurement precision while avoiding noise amplification.
Solution Approach 2:
The patent introduces an intermediary computational approach where raw microphone signals are processed through specialized algorithms that estimate spatial derivatives using finite difference methods or spherical harmonic transformations. This intermediary processing stage avoids direct differentiation of noisy measurements, instead using correlated signal processing techniques that preserve signal-to-noise ratio while extracting higher-order spatial information.
2Measurement precision
If more microphones are used to capture higher-order spatial derivatives, then spatial sound field decomposition accuracy is improved, but device complexity increases
Solution Approach 1:
The patent employs dynamic signal processing techniques where the system adaptively processes microphone signals based on the desired order of spatial derivatives. The processing pipeline dynamically adjusts computational complexity, using efficient algorithms such as spherical harmonic transforms for spherical arrays or finite difference schemes for planar arrays, allowing higher-order decomposition when needed while maintaining manageable device complexity through software-based flexibility.
Solution Approach 2:
The patent changes the parameter of microphone spacing and geometric arrangement to optimize the balance between measurement accuracy and device complexity. By carefully selecting inter-microphone distances relative to the acoustic wavelength and designing specific geometric configurations (such as regular tetrahedrons or spherical distributions), the system achieves sufficient accuracy for higher-order derivatives without requiring excessive numbers of microphones, thus controlling device complexity.
Data Source
AI summary
In certain embodiments, an article of manufacture, such as a cell phone, has a device body with a non-spheroidal shape, such as a parallelepiped, and microphones configured at different locations on the device body. A signal processing system processes the microphone signals to generate a plurality of different output beampatterns in at least two non-parallel directions, wherein, in generating at least one of the output beampatterns, the signal processing system takes into account effects of the device body on the incoming acoustic signal. Four or more microphones can be used to generate B format output beampatterns, such as three dipole beampatterns and an omnidirectional beampattern.