Handsfree Microphone Frequency Response and Directivity Switching

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Solution Overview

Problem

Existing hands-free communication microphones in vehicle cabins face challenges in providing optimal speech intelligibility and quality due to varying background noise conditions, as no single microphone type can effectively filter out all noise sources, leading to unsatisfactory performance in different driving scenarios.

Innovation Solution

A hands-free system that modifies microphone output based on a linearized correlation between the modified Speech Intelligibility Index (mSII) and Mean Opinion Score (MOS), using predetermined filter coefficients to adjust frequency response and directivity, switching between omnidirectional and unidirectional modes to optimize speech intelligibility and sound quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an omnidirectional microphone with flat frequency response is used, then speech quality is maintained across all directions, but speech intelligibility deteriorates in noisy environments

Engineering Contradiction:

Improvespeech qualityVSAvoidspeech intelligibility

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent implements dynamic switching between omnidirectional and unidirectional microphone modes based on real-time noise level detection. When background noise exceeds a threshold, the system transitions from omnidirectional to unidirectional mode to improve speech intelligibility while maintaining speech quality in normal conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the directional characteristics parameter of the microphone by applying different filter coefficients from lookup tables. This allows the same physical microphone to exhibit different polar patterns (omnidirectional or unidirectional) by modifying its frequency response characteristics through digital filtering

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If a unidirectional microphone is used, then speech intelligibility improves by spatially filtering noise, but noise rejecting performance deteriorates under wind turbulence conditions

Engineering Contradiction:

Improvespeech intelligibilityVSAvoidnoise rejecting performance

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The system continuously monitors the background noise spectrum and uses this feedback to determine the appropriate microphone mode. The noise detection algorithm analyzes spectral characteristics to distinguish between stationary noise (where unidirectional mode helps) and wind turbulence (where omnidirectional mode performs better), dynamically adjusting the microphone response accordingly

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The microphone system dynamically switches between unidirectional and omnidirectional modes based on real-time noise condition assessment. This dynamic adaptation allows the system to optimize speech intelligibility in stationary noise while avoiding the performance degradation that occurs with wind turbulence when using fixed unidirectional microphones

Inventive Principle:

Principle #15Dynamics

3Adaptability or versatility

If multiple microphones of different frequency response and directivity are used, then performance for different noise sources improves, but device complexity increases

Engineering Contradiction:

Improveperformance for different noise sourcesVSAvoidmicrophone system complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent makes a single omnidirectional microphone perform multiple functions by implementing digital signal processing that can create both omnidirectional and unidirectional response patterns. Through software-based filtering and beamforming algorithms, one physical microphone element provides the functionality of multiple specialized microphones, reducing hardware complexity while maintaining adaptability to different noise conditions

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Ease of operation

If a single predetermined threshold comparison is used for microphone switching, then switching decision simplicity is maintained, but switching accuracy deteriorates

Engineering Contradiction:

Improveswitching decision simplicityVSAvoidnoise vs. speech characteristics detection

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

Instead of using a single fixed threshold, the system employs multiple dynamically adjusted thresholds based on the detected noise spectrum characteristics. The threshold values are adapted according to the type of noise detected (stationary vs. wind turbulence), allowing accurate differentiation between noise and speech while maintaining simple automated switching logic through predefined decision rules

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12073848B2System and method for switching a frequency response and directivity of microphone

Publication Date: 2024.08.27 HARMAN INT IND INC

AI summary

A handsfree system and method to modify at least one microphone output based on a linearized correlation between a modified Speech Intelligibility Index (mSII) and a Mean Opinion Score (MOS). The at least one microphone output signal is compared to predetermined thresholds for the mSII that correspond to a noise condition and the microphone output signal is modified to optimize Speech Intelligibility and Sound Quality for the noise condition.