Forward Beamforming Microphone Array for Thin Flush-Mounted Devices
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Solution Overview
Problem
Existing acoustic beamforming systems in thin or flush-mounted devices suffer from low sensitivity and insufficient directionality due to limited spacing between sound ports, leading to poor signal-to-noise ratios and inadequate noise rejection.
Innovation Solution
A combination of directional and omnidirectional microphones, arranged in specific configurations, with a processing system to create a beamformed directional pattern that points forward, using differential output signals and matching filters to enhance directionality and reject background noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the device is made thin or flush-mounted, then the device form factor is compact, but the spacing between sound ports becomes small leading to low sensitivity and low signal-to-noise ratio
Solution Approach 1:
The patent transitions from a single-dimensional spacing problem (distance between sound ports along the thickness axis) to a multi-dimensional solution by arranging microphones in a planar array configuration. The directional microphones are positioned at different lateral locations (left and right of the omnidirectional microphone) rather than requiring significant separation along the thickness axis, enabling effective beamforming in a thin device form factor.
Solution Approach 2:
The patent divides the audio capture function into multiple specialized components: one omnidirectional microphone and multiple directional microphones, each with specific pickup patterns. This segmentation allows each microphone type to perform its specialized function optimally, with the processing system combining their outputs to achieve superior directional performance and noise rejection in a compact configuration.
2Ease of operation
If directional microphones are integrated with sound ports spaced apart along device thickness, then directional pickup is achieved, but device thickness increases reducing ease of flush mounting
Solution Approach 1:
The patent resolves the conflict between flush mounting and directional pickup by moving the sound port separation from the thickness dimension to the lateral dimension. The directional microphones are positioned at different horizontal locations (left and right of center) rather than requiring vertical separation through device thickness, enabling flush mounting while maintaining directional capability.
3Reliability
If an array of omnidirectional microphones is used to create directional pickup pattern, then directional performance is improved, but the size of the array becomes too large
Solution Approach 1:
The patent applies local quality by assigning different pickup pattern characteristics to different microphone positions. Directional microphones with figure-8 or hypercardioid patterns are positioned at specific lateral locations (left and right of the omnidirectional microphone), while the omnidirectional microphone is positioned at the center. This localized specialization of microphone types at different positions enables effective directional beamforming with a more compact array than would be required using only omnidirectional microphones.
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
Maintains a compact form factor while providing improved directional performance by effectively capturing audio in front of the device while attenuating surrounding noise.
Implementation Method 1
The processing system is configured to combine outputs of the plurality of microphones to create a beamformed directional pattern that points at least approximately in the forward direction
Implementation Method 2
The first directional microphone is configured to generate a first directional output signal having first dipole beam pattern including a first positive dipole portion and a first negative dipole portion that is out of phase with the first positive dipole portion
Data Source
AI summary
An acoustic beamforming system includes a plurality of microphones including at least a first directional microphone having a first directional beam pattern, the first directional microphone arranged such that the first directional beam pattern points in a first direction other than a forward direction, a second directional microphone having a second directional beam pattern, the second directional microphone arranged such that the second directional beam pattern points in a second direction other than the forward direction, and an omnidirectional microphone. The acoustic beamforming system also includes a processing system configured to combine outputs of the plurality of microphones to create a beamformed directional pattern that points at least approximately in the forward direction.