Microphone Array with Asymmetric Spacing for Spatial Audio

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Solution Overview

Problem

Existing multichannel audio systems struggle to provide consistent and accurate spatial audio reproduction across a wide listening area, with commercially available systems often favoring the front direction and requiring significant computational resources or engineering adjustments, while existing solutions like Ambisonics and wave-field synthesis have limitations in domestic settings.

Innovation Solution

A microphone array with carefully designed directivity functions to minimize cross-talk between non-adjacent microphones and approximate stereophonic panning curves, ensuring that sound sources are effectively captured by only two consecutive microphones, thereby improving auditory localization and reducing cross-talk, and incorporating a panoramic audio recording system with equiangularly arranged microphones on a circular arc.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If commercially available multichannel systems employ uneven loudspeaker positions favoring the front direction, then front direction reproduction is improved, but spatial consistency across different directions deteriorates

Engineering Contradiction:

Improvefront direction reproduction accuracyVSAvoidspatial consistency across directions

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies asymmetry by using unevenly spaced microphones in the azimuth direction (different angular intervals) while maintaining uniform spacing in the elevation direction, creating a directional bias toward the front that matches human listening behavior and improves front direction reproduction while maintaining overall spatial consistency

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent implements local quality by applying different angular intervals between microphones in different azimuth regions, with smaller intervals in the front direction and larger intervals in side/rear directions, allowing optimized reproduction quality for each spatial region

Inventive Principle:

Principle #3Local quality

2Measurement precision

If Ambisonics system is used to achieve perfect sound field reconstruction, then reconstruction accuracy is improved, but listening area width deteriorates

Engineering Contradiction:

Improvesound field reconstruction accuracyVSAvoidlistening area width

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent segments the sound field into different spatial regions (front, side, rear) and applies different microphone spacing strategies to each region, allowing optimized reconstruction accuracy in the front direction while extending acceptable reconstruction to wider areas through the uneven distribution pattern

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the spatial distribution parameters of microphones from uniform to non-uniform spacing, with varying angular intervals that optimize the sound field reconstruction characteristics across different listening positions and directions

Inventive Principle:

Principle #35Parameter changes

3Area of stationary object

If wave-field synthesis is used to provide panoramic audio, then listening area coverage is improved, but computational resources and channel requirements deteriorate

Engineering Contradiction:

Improvelistening area coverageVSAvoidcomputational resources and channel requirements

Core Design Contradiction:

Area of stationary objectVSDevice complexity

Solution Approach 1:

The patent extracts only the essential spatial sampling information needed for panoramic reproduction by using a reduced number of microphones with non-uniform spacing, eliminating the need for complex computational processing and large channel counts required by wave-field synthesis while maintaining wide area coverage

Inventive Principle:

Principle #2Taking out (Extraction)

4Area of stationary object

If more microphones are added to improve panoramic audio recording, then spatial coverage is improved, but cross-talk between non-adjacent microphones deteriorates

Engineering Contradiction:

Improvespatial coverageVSAvoidcross-talk between microphones

Core Design Contradiction:

Area of stationary objectVSLoss of information

Solution Approach 1:

The patent uses asymmetric microphone spacing with smaller angular intervals in the front direction and larger intervals in side/rear directions, which reduces cross-talk between non-adjacent microphones in the front region where listeners are primarily positioned, while maintaining adequate spatial coverage

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentUS8976977B2Microphone array

Publication Date: 2015.03.10 CVETKOVIC ZORAN

AI summary

A microphone array, comprising N microphones, wherein N is greater than or equal to 3 is provided. The microphones are substantially equiangularly arranged over a circular arc subtending an angle ε, wherein ε is less than or equal to 2π, with the directional axes of the N microphones facing substantially radially outwards. Each of the N microphones have a substantially common directivity function Γ(θ) defining the directional response of the microphone, wherein θ=0 is the directional axis, and the directivity function Γ(θ) is arranged such that a sound source in acoustical free field is effectively captured by no more than two consecutive microphones in the array. By arranging the directivity function in this manner crosstalk between non-adjacent microphones can be minimized, which has been shown to improve auditory localization performance.