Ceiling Microphone Assembly Quarter Toroid Pattern

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Solution Overview

Problem

Conventional microphones in teleconferencing systems suffer from audio distortion due to reverberant sound and noise interference, particularly when omni directional microphones receive audio from all directions, leading to poor audio quality and the need for frequent repositioning of directional microphones to maintain optimal sensitivity.

Innovation Solution

A ceiling-mounted microphone assembly with an L-shaped structure featuring two microphone elements and a subtractor and equalizer configuration, generating a quarter toroid sensitivity pattern that maximizes direct sound capture while minimizing reverberant sound and noise interference, independent of elevation angle.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If omni directional microphones are used to capture audio from all directions, then coverage of multiple participants is improved, but audio quality deteriorates due to reverberant sound and noise interference

Engineering Contradiction:

Improvecoverage of multiple participantsVSAvoidreverberant sound and noise interference

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The microphone system is segmented into multiple directional elements (at least two microphones with different directivity patterns) that capture sound from different directions. By dividing the omnidirectional capture function into segmented directional components, the system can selectively combine signals to achieve broad coverage while rejecting reverberant sound and noise from specific directions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the sensitivity pattern are assigned different qualities - high sensitivity in directions where direct sound from participants is expected, and low sensitivity in directions where reverberant sound and noise are predominant. This local differentiation of sensitivity allows the microphone to optimize audio quality in specific spatial zones while maintaining overall coverage.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If directional microphones are used to minimize reverberant sound, then audio quality is improved, but the need for frequent repositioning increases to maintain optimal sensitivity

Engineering Contradiction:

Improvereverberant sound minimizationVSAvoidfrequency of repositioning

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

The microphone system is designed to perform multiple functions simultaneously - it provides directional noise rejection like specialized directional microphones, while also offering broad coverage of multiple participants like omnidirectional microphones. This multi-functionality eliminates the need for repositioning to adapt to different participant configurations.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system dynamically combines signals from multiple microphone elements with different directivity patterns, allowing the overall sensitivity pattern to adapt to different acoustic conditions and participant positions without physical repositioning. The electronic signal processing enables dynamic adjustment of the effective pickup pattern.

Inventive Principle:

Principle #15Dynamics

3Measurement precision

If microphones are positioned closer to the sound source, then direct sound capture is improved, but the room radius constraint limits placement flexibility

Engineering Contradiction:

Improvedirect sound capture levelVSAvoidmicrophone placement flexibility

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The microphone system employs asymmetric signal processing where signals from different microphone elements are combined with different weights and phases. This asymmetric combination creates a directional sensitivity pattern that emphasizes direct sound from participant directions while suppressing reverberant sound, effectively extending the usable distance beyond the conventional room radius constraint.

Inventive Principle:

Principle #4Asymmetry

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

The solution enhances audio quality by reducing reverberant sound and noise interference, maintaining optimal sensitivity without the need for frequent repositioning, and provides a consistent directivity pattern that covers multiple participants around a conference table.

Implementation Method 1

acoustical interaction of the two planar surfaces with the two microphone elements

Methodology Applied

Scientific EffectSound wave reflection: Reflection

Data Source

PatentUS8437490B2Ceiling microphone assembly

Publication Date: 2013.05.07 CISCO TECHNOLOGY INC

AI summary

A video teleconferencing directional microphone has two surfaces joined with an angle of 90° relative to each other, a first omni directional microphone element arranged adjacent to the intersection between the two surfaces. The ceiling microphone assembly also includes a second omni directional microphone element arranged at a predetermined distance (d) from both surfaces. A subtractor subtracts the output of the first microphone element from the output of the second microphone element, and the output of the subtractor is equalized by an equalizer (Heq) to generate an equalized output. The surfaces and subtractor generates a quarter toroid directivity pattern for the ceiling microphone assembly. The quarter toroid sensitivity pattern increases sensitivity in the direction of a sound source of interest, but reduces sensitivity to any sound waves generated by noise sources at other locations or reverberations.