Nested Microphone Array for Directional Polar Patterns

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Solution Overview

Problem

Conferencing microphones struggle to achieve high performance directional polar patterns and effective noise isolation due to physical constraints and frequency response irregularities, particularly with MEMS microphones, which are omnidirectional and lack the necessary signal-to-noise ratio and wideband audio coverage required for conferencing environments.

Innovation Solution

A microphone array design featuring nested sets of microphone elements spaced apart to cover specific frequency bands, combined using beamforming techniques to generate directional polar patterns such as toroidal or cardioid, with orthogonal arrays creating planar directional pickup, and crossover filtering to optimize frequency response across the audible bandwidth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple cartridges are used to achieve directional polar patterns, then the microphone can capture sound from multiple audio sources, but the cartridges cannot be co-located and thus produce frequency response irregularities and interference

Engineering Contradiction:

Improvedirectional polar pattern capabilityVSAvoidfrequency response uniformity

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The microphone array is divided into multiple independent microphone elements arranged in specific geometric patterns (e.g., circular array with multiple microphones around a central axis). Each microphone element captures sound independently, and the directional polar pattern is achieved through signal processing rather than physical cartridge arrangement, eliminating frequency response irregularities caused by physical separation.

Inventive Principle:

Principle #1Segmentation

2Length of moving object

If conventional MEMS microphones are used, then the package size is small and power consumption is low, but the polar pattern is inherently omnidirectional and cannot provide directional sensitivity

Engineering Contradiction:

Improvemicrophone package sizeVSAvoiddirectional polar pattern capability

Core Design Contradiction:

Length of moving objectVSAdaptability or versatility

Solution Approach 1:

Multiple MEMS microphone elements are combined into an array configuration where each small omnidirectional element contributes to the overall directional response. The individual omnidirectional polar patterns of the small MEMS microphones are merged through spatial arrangement and signal processing to create a composite directional polar pattern, achieving directionality without requiring large individual microphone elements.

Inventive Principle:

Principle #5Merging (Combining)

3Adaptability or versatility

If existing toroidal microphones are used, then omnidirectional detection in the plane is achieved, but the microphones are physically large and have high self-noise

Engineering Contradiction:

Improveomnidirectional detection capabilityVSAvoidmicrophone physical size

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The physical mechanical structure of large toroidal microphones is replaced with a virtual toroidal polar pattern created through signal processing of multiple small microphone elements. Instead of using a large physical structure to achieve omnidirectional detection, the system uses computational methods to synthesize the toroidal response from multiple small MEMS microphones arranged in a compact configuration.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Loss of time

If multiple cartridges are positioned close together to co-locate them, then simultaneous sound detection is improved, but interference and reflections within and between cartridges increase

Engineering Contradiction:

Improvetime delay between sound detectionVSAvoidinterference and reflections

Core Design Contradiction:

Loss of timeVSObject-affected harmful factors

Solution Approach 1:

Each microphone element in the array is positioned at a specific location with optimized spacing to minimize mutual interference. The local quality of each microphone element's polar pattern is maintained (omnidirectional for MEMS), while the global arrangement creates the desired directional response. This local optimization ensures that each element captures sound accurately without significant interference from neighboring elements.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS11800281B2Pattern-forming microphone array

Publication Date: 2023.10.24 SHURE ACQUISITION HLDG INC

AI summary

Embodiments include a planar microphone array comprising a first linear array arranged along a first axis; and a second linear array arranged along a second axis orthogonal to the first axis, a center of the second linear array aligned with a center of the first linear array, wherein each of the first linear array and the second linear array comprises a corresponding first set of microphone elements nested within a corresponding second set of microphone elements, and each set of microphone elements is arranged symmetrically about the center of the corresponding linear array, such that the first linear array and the second linear array are configured to generate a steerable directional polar pattern, the microphone elements of each linear array configured to capture audio signals. Embodiments also include a microphone system comprising the same and a method performed by processor(s) to generate an output signal for the same.