Ambisonic Microphone Array for Discreet Room Coverage
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Solution Overview
Problem
Current acoustic capture devices for ambient intelligence systems face challenges in uniformly covering large spaces with minimal sensors while maintaining discretion and aesthetics, as they are often limited by the number of microphones and are not optimized for wideband signal capture, leading to poor signal-to-noise ratios and interference from ambient noise and furniture.
Innovation Solution
A sound capture device with a distribution of microphone capsules over a portion of a sphere, using ambisonic representation and processing to identify sound sources by retaining only symmetrical spherical harmonics, allowing for discreet placement and reducing the number of sensors needed, while leveraging reflections from walls and ceilings to enhance signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a complete spherical microphone array is used to achieve omnidirectional coverage, then the acoustic capture coverage is improved, but the number of sensors and device complexity increase significantly
Solution Approach 1:
The patent divides the spherical microphone array into discrete segments (e.g., 8 quadrants or more) rather than using a complete sphere. Each segment contains a subset of microphones that collectively provide omnidirectional coverage when combined with image microphones generated through acoustic reflection modeling. This segmentation reduces the number of physical sensors while maintaining coverage effectiveness.
Solution Approach 2:
The patent creates virtual copies of physical microphones through acoustic reflection modeling. By modeling reflections from walls and ceilings, the system generates image microphones that replicate the functionality of physical microphones in reflected positions. This copying approach allows the system to achieve complete spherical coverage with fewer physical sensors, as the image microphones compensate for the missing physical elements.
2Area of stationary object
If microphone arrays are placed in the middle of the room to achieve omnidirectional coverage, then the capture coverage is improved, but the device becomes less discreet and more visible
Solution Approach 1:
The patent transitions from a horizontal placement strategy (microphones in the middle of the room) to a vertical placement strategy (microphones on the ceiling). By moving to another dimension (vertical space), the system achieves omnidirectional coverage while maintaining discretion, as ceiling-mounted devices are less visually obtrusive than table-level voice assistant devices. The spherical array geometry naturally extends this advantage by providing 360-degree horizontal coverage from elevated positions.
Solution Approach 2:
The patent uses acoustic reflections from walls and ceilings as intermediaries to extend the capture coverage. Instead of requiring physical microphones in all directions, the system uses reflected sound waves as intermediaries to bring information from directions where physical microphones would be needed but are not actually present. This allows discreet ceiling placement while maintaining comprehensive coverage through the intermediary effect of acoustic reflections.
3Area of stationary object
If linear or spherical microphone array geometries are used, then the capture coverage is improved, but the number of sensors required increases for effective capture
Solution Approach 1:
The patent employs dynamic signal processing that adapts to the acoustic environment rather than relying on fixed geometric arrangements alone. The system dynamically models acoustic reflections and adjusts the contribution of different microphone segments and image microphones based on the actual room acoustics. This dynamic approach allows effective capture with fewer sensors, as the system optimizes its response based on real-time acoustic conditions rather than relying solely on static geometric optimization.
4Reliability
If voice assistants are placed at human height to enable interaction, then the voice recognition performance is improved, but the capture is degraded by nearby noise sources and furniture obstruction
Solution Approach 1:
The patent counteracts the harmful effects of nearby noise sources and furniture obstruction by using acoustic reflection modeling to create image microphones that compensate for the degraded signal quality. The image microphones generated from wall and ceiling reflections provide alternative signal paths that bypass the obstruction and noise interference affecting the direct microphones. This counterweight approach balances the negative impact of furniture and noise by introducing compensating signal pathways through reflected sound.
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
The solution provides effective, discreet, and compact acoustic coverage of entire rooms with improved signal-to-noise ratios, enabling reliable detection of sound sources and reducing interference, suitable for both home and professional use in audio ambient intelligence systems.
Implementation Method 1
a plurality of microphone capsules (for example electrostatic or piezoelectric capsules, electrets, or MEMS)
Implementation Method 2
a plurality of microphone capsules (for example electrostatic or piezoelectric capsules, electrets, or MEMS)
Implementation Method 3
They are equipped with an array of microphones (often circular) in order to be able to focus the capture on the source of interest (meaning the user) by applying antenna processing (typically beamforming methods)
Implementation Method 4
matrix the signals in an ambisonic representation which retains only the ambisonic components associated with spherical harmonics that are symmetrical in relation to at least two of the aforementioned planes
Implementation Method 5
leveraging reflections from walls and ceilings to enhance signal quality
Data Source
AI summary
A sound capture device is disclosed, including plural microphone capsules, distributed over portion P of sphere S circumscribed between two or three planes perpendicular to each other, the three planes intersecting at a point corresponding to the center of the sphere S, and the two planes intersecting at a straight line passing through the center of the sphere S, and the sphere portion P being such that P=n S/8, with n=1,2; and a processing unit connected to the capsules to receive the signals captured by the capsules. The processing unit is arranged to matrix the signals in an ambisonic representation which retains only the ambisonic components associated with spherical harmonics that are symmetrical in relation to at least two of the aforementioned planes, and process a matrix thus obtained to identify a sound source surrounding the sphere portion and interpret a sound signal from the source.