3D Microphone Array with Optical MEMS for Compact Sound Localization
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Solution Overview
Problem
Conventional microphone arrays for sound detection and beam forming face challenges in achieving good directionality and spatial resolution due to limitations in aperture size and frequency range, requiring large apertures and numerous transducers, which increase volume and cost, and are hindered by side lobes and spatial aliasing.
Innovation Solution
The apparatus incorporates a display with integrated microphone stacks and elastic connectors, featuring microelectromechanical transducer arrays with optical reading devices, allowing for compact installation in limited spaces while maintaining sensitivity and directionality, using 2D materials for membranes that provide robustness and resistance to environmental impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large aperture is used to achieve good directionality at lower frequencies, then spatial resolution is improved, but the device volume and cost increase
Solution Approach 1:
The patent transitions from conventional planar microphone arrays to a three-dimensional volumetric array configuration. Multiple microphone capsules are positioned at different depths and lateral positions within a compact housing, creating a 3D spatial distribution that achieves superior directionality and spatial resolution without requiring a large aperture. This volumetric arrangement allows the system to resolve sound sources in three-dimensional space while maintaining a compact form factor suitable for mobile devices.
Solution Approach 2:
The patent implements a nested structure where multiple microphone capsules are arranged in concentric or layered configurations within a compact housing. The capsules are positioned at different radial distances from a central axis and at different axial positions, creating a nested volumetric pattern. This nested arrangement maximizes the effective aperture within a minimal volume, allowing the system to achieve good directionality at low frequencies without increasing device size.
2Device complexity
If the distance between transducers is increased to reduce the number of transducers, then device complexity is reduced, but side lobes and spatial aliasing occur at higher frequencies
Solution Approach 1:
The patent applies different spacing configurations to different regions of the array. The volumetric distribution allows for optimized local spacing between adjacent capsules in various directions, ensuring that the maximum spacing in any direction remains below half the wavelength of the highest frequency of interest. This non-uniform, directionally-adapted spacing maintains frequency response reliability while reducing the total number of transducers compared to a uniform planar array.
Solution Approach 2:
By distributing microphones in three dimensions rather than a single plane, the system achieves equivalent or superior frequency response characteristics with fewer elements. The 3D configuration provides redundant spatial sampling that suppresses side lobes and prevents spatial aliasing more effectively than a 2D array with the same number of transducers, while requiring fewer total elements than a densely-sampled planar array.
3Reliability
If capacitive MEMS microphones are used as discrete components, then sound detection capability is achieved, but substantial space and volume are required
Solution Approach 1:
The patent combines multiple microphone capsules and their associated back-volumes into a single integrated volumetric array structure. Rather than using discrete capacitive MEMS microphones that each require substantial individual back-volume space, the system employs multiple smaller acoustic sensors positioned within a shared acoustic environment. This merging of functions allows the array to achieve equivalent sound detection capability with significantly reduced total volume, as the back-volumes are shared and the capsules are densely packed in three-dimensional space.
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 configuration enables effective sound detection, localization, and beam forming at low frequencies down to 1 kHz with improved signal-to-noise ratio and reduced volume, allowing for miniaturization in devices like smartphones, while protecting membranes from external forces.
Implementation Method 1
an optical reading device, which is configured to detect the displacement of each membrane
Implementation Method 2
a microelectromechanical transducer array, the transducer array comprising a plurality of membranes and corresponding integrated back-volumes
Data Source
AI summary
An apparatus for sound detection, sound localization and beam forming comprises a display and a plurality of microphone stacks, wherein the display surrounds each microphone stack in lateral directions. The apparatus further comprises a plurality of elastic connectors, wherein each elastic connector surrounds one respective microphone stack in lateral direction and mechanically connects the respective microphone stack with the display. Each microphone stack further comprises a microelectromechanical transducer array, the transducer array comprising a plurality of membranes, in particular nano-membranes, and corresponding integrated back-volumes, the back-volumes being arranged under the membranes. An optical reading device is configured to separately detect the displacement of each membrane.