Augmented Elliptical Microphone Array Vertical Beampattern Control
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Solution Overview
Problem
Circular microphone arrays struggle to control the beampattern in the vertical plane due to modal aliasing, leading to increased sensitivity in the vertical direction as frequency increases, which limits their directional performance and frequency range.
Innovation Solution
Incorporating a single central microphone or additional concentric circular arrays into the circular microphone array allows for control over the vertical beampattern response by accessing and separating aliased vertical spherical harmonic modes, thereby reducing modal aliasing and enhancing directional gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a standard circular microphone array is used, then the beam can be steered to any angle in the horizontal plane, but the vertical beampattern response cannot be controlled and may exceed the in-plane response due to modal aliasing
Solution Approach 1:
The patent transitions from a two-dimensional circular array to a three-dimensional configuration by adding a central microphone at the center of the circular array. This dimensional enhancement enables control over vertical beampattern response while preserving horizontal beam steering capability, resolving the contradiction between ease of operation in horizontal plane and reliability in vertical plane control
2Measurement precision
If the frequency increases in a circular microphone array, then the directional performance may improve, but the sensitivity in the vertical direction increases due to modal aliasing
Solution Approach 1:
The patent converts the harmful effect of modal aliasing in vertical modes into a beneficial control mechanism. By adding the central microphone, the system gains the ability to independently control vertical spherical harmonic modes, transforming the previously uncontrollable and harmful vertical sensitivity increase into a controllable parameter that can be optimized for directional performance without harmful vertical leakage
3Reliability
If a single central microphone is added to the circular array, then control over vertical beampattern is achieved, but the device complexity increases
Solution Approach 1:
The patent segments the microphone array into two distinct functional components: the circular array elements that handle horizontal beam steering, and the central microphone that handles vertical mode control. This segmentation allows each component to be optimized for its specific function while working together to achieve full spatial response control, minimizing the increase in device complexity
Data Source
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AI summary
In one embodiment, an audio system has a microphone array and a signal processing subsystem that processes audio signals generated by the microphone array to produce an output beampattern. The microphone array has (i) a plurality of microphones arranged in a circular portion and (ii) a center microphone. The signal processing subsystem has (1) a decomposer that spatially decomposes the microphone audio signals to generate a plurality of eigenbeams and (2) a beamformer that generates the output beampattern as a weighted sum of the eigenbeams. By adding the center microphone, the audio system is able to provide some degree of control over the beamforming in the vertical direction as well as provide reduction of modal aliasin.