Orthogonal Microphone Array Layout for Stable Beam Directivity
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Solution Overview
Problem
Existing array microphones, particularly those using MEMS transducers, suffer from omnidirectional sensitivity and fixed form factors, leading to unwanted noise pickup and limited placement options in conferencing environments, while traditional microphones face complexity and frequency response irregularities.
Innovation Solution
A one-dimensional array microphone design with harmonically nested microphones along orthogonal axes, utilizing beamforming techniques to achieve frequency-dependent directivity, high signal-to-noise ratio, and improved rear rejection, allowing for consistent directionality across various frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a two-dimensional microphone array is used to capture spatial information, then the coverage area and spatial resolution are improved, but the directivity pattern becomes blurred and loses directional selectivity
Solution Approach 1:
The patent segments the microphone array into multiple independent sub-arrays, where each sub-array captures acoustic information from a specific spatial region. This segmentation allows the system to maintain both spatial resolution and directivity by processing information from different sub-arrays separately, preventing the directivity blur that would occur in a single large array.
Solution Approach 2:
The patent introduces a temporal dimension to the spatial measurement problem by using time-delayed signal processing. Instead of relying solely on spatial arrangement to achieve directionality, the system uses time delays in signal processing to reconstruct directional information, effectively adding a time dimension to compensate for the spatial blurring.
2Measurement precision
If the microphone array elements are spaced closer together to improve spatial resolution, then the directivity pattern deteriorates due to increased grating lobes
Solution Approach 1:
The patent extracts and eliminates the harmful grating lobes by using signal processing techniques to identify and remove spatial frequency components that correspond to grating lobes. By separating the desired main lobe signal from the harmful grating lobes in the frequency domain, the system maintains high spatial resolution without the artifacts introduced by closely spaced elements.
Solution Approach 2:
The patent converts the harmful effect of closely spaced elements (which create grating lobes) into a beneficial feature by using the time-delayed signal processing to enhance spatial resolution. The system exploits the phase differences introduced by close spacing, through appropriate signal processing, to achieve super-resolution capability that would normally be considered a defect.
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 design provides enhanced directivity and noise rejection, enabling high-performance audio capture in conferencing environments with a thin, low-profile form factor, suitable for capturing multiple audio sources with reduced complexity and cost.
Implementation Method 1
a first two-dimensional array of microphones arranged in a first plurality of rows and a first plurality of columns
Data Source
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AI summary
Embodiments include an array microphone comprising a plurality of microphone sets arranged in a linear pattern relative to a first axis and configured to cover a plurality of frequency bands. Each microphone set comprises a first microphone arranged along the first axis and a second microphone arranged along a second axis orthogonal to the first microphone, wherein a distance between adjacent microphones along the first axis is selected from a first group consisting of whole number multiples of a first value, and within each element, a distance between the first and second microphones along the second axis is selected from a second group consisting of whole number multiples of a second value.