Directional Sound Enhancement Using Coherence Analysis in Small Microphone Arrays

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Solution Overview

Problem

Conventional beamforming methods for directional audio enhancement in noisy environments require multiple microphones spaced over a large volume, limiting their effectiveness in small microphone arrays used in mobile devices and wearable technology.

Innovation Solution

A system and method that uses a processor to calculate the coherence between two microphones, determine the phase angle, and update filter coefficients to enhance directional sensitivity, allowing for improved signal-to-noise ratio (SNR) in small microphone arrays by selectively filtering sound signals based on directionality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional beamforming methods are used with multiple microphones spaced over a large volume, then directional audio enhancement and signal-to-noise ratio improvement are achieved, but device size and complexity increase

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidmicrophone array volume

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The patent replaces the mechanical approach of physically spacing microphones over a large volume with a computational signal processing approach. By using coherence analysis and adaptive filtering algorithms, the system achieves directional enhancement and SNR improvement through software-based spatial filtering rather than requiring large physical microphone separation distances.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the approach from physical parameter (microphone spacing distance) to computational parameter (coherence threshold and filter coefficients). By adjusting these parameters dynamically based on acoustic scene analysis, the system achieves directional enhancement without requiring large physical volume for microphone placement.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If microphones are spaced wide apart to achieve directional enhancement, then receive gain improves, but the system becomes unsuitable for small mobile devices

Engineering Contradiction:

Improvereceive gainVSAvoidmicrophone array configuration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent substitutes mechanical microphone array configuration with computational signal processing. Instead of relying on wide physical spacing to achieve receive gain, the system uses coherence-based adaptive filtering to create directional sensitivity through software, making the system suitable for compact mobile devices with closely spaced microphones.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent transitions from spatial dimension (physical microphone spacing) to computational dimension (signal processing operations). By performing coherence analysis and adaptive filtering in the signal processing domain, the system achieves directional enhancement without requiring large physical dimensions for microphone placement.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

This approach enhances speech intelligibility and situational awareness in noisy environments, enabling effective voice communication and sound localization in mobile and wearable devices without the need for extensive microphone spacing, thereby improving the SNR and user experience.

Implementation Method 1

calculate the coherence between the first and second microphones, determine a measured frequency dependent phase angle of the complex coherence

Methodology Applied

Scientific EffectCoherence analysis:

Implementation Method 2

determine a measured frequency dependent phase angle of the complex coherence, comparing the measured phase angle to a reference phase angle

Methodology Applied

Scientific EffectPhase angle determination:

Implementation Method 3

updating the set of filter coefficients to enhance directional sensitivity of the microphone signal, filtering the first and second microphone signals with the updated filter coefficients

Methodology Applied

Scientific EffectAdaptive filtering: Filter (electronic)

Data Source

PatentUS9271077B2Method and system for directional enhancement of sound using small microphone arrays

Publication Date: 2016.02.23 ST PORTFOLIO HLDG LLC

AI summary

Herein provided is a method and system for directional enhancement of a microphone array comprising at least two microphones by analysis of the phase angle of the coherence between at least two microphones. The method can further include communicating directional data with the microphone signal to a secondary device, and adjusting at least one parameter of the device in view of the directional data. Other embodiments are disclosed.