Microphone Array Fault Detection via Cross-Correlation

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Solution Overview

Problem

Traditional energy-based fault detection methods for microphone arrays in portable communication devices often fail to distinguish between faulty microphones and those subjected to wind noise, leading to false triggers and impaired communication.

Innovation Solution

A correlation-based method using both magnitude and phase between multiple microphones to determine faulty microphones, employing smoothed normalized correlation (SNC) and bandpass filtering to isolate failed microphones while avoiding false triggers under windy conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional energy-based failure detectors are used, then faulty microphones can be detected, but false triggers occur in windy environments

Engineering Contradiction:

Improvefault detection accuracyVSAvoidfalse triggers from wind noise

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an intermediary correlation analysis mechanism that compares signals across multiple microphones. Instead of directly detecting faults through energy levels (which are affected by wind), the system uses correlation as a mediator to distinguish between correlated wind noise across all mics and uncorrelated fault signals from individual microphones, thereby eliminating false triggers while maintaining reliable fault detection

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the traditional energy-based detection mechanism with a correlation-based detection mechanism. This substitution transforms the detection approach from measuring signal power (which cannot distinguish wind from faults) to measuring signal relationships between microphones, where wind noise appears as correlated variations across all microphones while faults appear as uncorrelated anomalies in individual microphones

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If energy-based detection is used, then simple fault detection is achieved, but distinction between faulty and wind-noise affected microphones is lost

Engineering Contradiction:

Improvedetection method simplicityVSAvoidmicrophone status differentiation

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent transitions from one-dimensional energy-based detection to multi-dimensional correlation-based detection. By analyzing the relationships between multiple microphones across different time points and frequency components, the system adds dimensional depth to the detection process, enabling differentiation between wind-affected and faulty microphones while maintaining computational feasibility through efficient correlation algorithms

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS10405115B1Fault detection for microphone array

Publication Date: 2019.09.03 MOTOROLA SOLUTIONS INC

AI summary

Reliable detection of a microphone failure along with corrective action are provided for a portable communication device having multiple microphones. The faulty microphone detection uses a correlation based metric between three (3) or more microphones. The approach is based on full cross correlation, including phase as well as magnitude, between unique microphone pairs for isolating a faulty microphone condition. The approach allows for the determination of precisely which microphone has failed and minimizes false triggers under windy conditions within a microphone array.