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CHAPTeR 5: AUTOMATIC MIC MIXING

iNTeLLigibLe, reLiAbLe AUDiO

Systems that produce intelligible and reliable audio are key to facilitating effective communication. A quality conferencing 
system meets the following objectives:

The audio must be transparent. Users should not have to think about the audio.

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The audio must not fatigue the users. Distorted, noisy audio will cause users to break off discussions before a 

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natural conclusion occurs. It will also fatigue the users, and potentially reducing their effectivness.
Since 10% of our population is hearing impaired, the audio system must be capable of producing effective results 

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for all users.
The audio system must be reliable.

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Automatic microphone mixing is key to producing intelligible, reliable conferencing audio. by turning the level of 
microphones up when a person speaks, an automatic microphone mixer will reduce the pickup of reverberation and 
noise—the two major culprits in making voice communications difficult. The more an the automatic mixer can prevent 
false activation of microphones by signals other then local talkers, the higher the clarity of the audio.

Celling

Microphones

Figure 5.1  

In figure 5.1, direct audio from a person’s voice is picked up by several microphones connected to a microphone mixer 
that has all microphones on at all times. Direct and reflected audio (reverberation) is picked up by all the microphones. 
In addition, the reflected audio will have a variety of delays, depending on how far it has traveled in the room. If the 
reflected audio is high enough in level, participants will have a difficult time understanding the audio. When people hear 
reverberated audio, their initial response is to turn up the volume. In other words, increased noise and reverberation hurts 
audio intelligibility and increases listener fatigue.

There are several strategies that can reduce reverberation and noise:

keep microphones close to the participants

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Activate only those microphones where voice audio is present

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Use directional microphones

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Acoustically treat the room to reduce reverberation and noise

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eliminate or reduce the source of noise

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Содержание Converge Pro

Страница 1: ...Converge Pro White Paper...

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Страница 3: ...ommunications Inc All rights reserved No part of this document may be reproduced in any form or by any means without written permission from ClearOne Communications Inc Printed in the United States of...

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Страница 5: ...ation 16 CHAPTER 3 Processing Blocks 17 Filters 17 CHAPTER 4 Inputs and Outputs 19 Mic Line inputs 19 Line Inputs 20 Outputs 20 CHAPTER 5 Automatic Mic Mixing 21 Intelligible Reliable Audio 21 Microph...

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Страница 7: ...microphone compatibility provides greater design and configuration flexibility Advanced noise cancellation reduces background noise caused by fans HVAC systems and other relatively constant backgroun...

Страница 8: ...agnostics from any PC 32 programmable presets for instant configuration changes Connect multiple Converge Pro s to create a single system Logic ports for external control and status monitoring Distrib...

Страница 9: ...ine Inputs Line Inputs Power Amp Processing Channels Fader Channels Output Telco E Bus Converge Pro 880TA New 8 4 4 35W 8 0 8 1 Yes Converge Pro 880T 8 4 1 5W 8 4 12 1 Yes Converge Pro 880 8 4 8 4 12...

Страница 10: ...d pre configured AV devices custom AV devices can be created by the user of Converge Console Object Database In addition to using AV devices Converge Console allows you to create save and apply Channe...

Страница 11: ...object it appears in the object pane of Console To use a macro object drag it from the Objects Pane and drop it onto the Macro Command List portion of the Macro Tab screen Preset Objects Preset object...

Страница 12: ...Front Panel SELECT MENU ESC 1 2 3 4 5 6 7 8 ClearOne Converge 880TA DO CONVERGE880 91 1 1 1 IPA 0 0 0 0 A C B D E F G I H SELECT MENU ESC 30 10 4 0 4 8 12 METER 1 2 3 4 5 6 7 8 CONVERGE PRO 880 ClearO...

Страница 13: ...he highlighted option LED Bar Meter G Displays the audio level of a selected input output processing or fader channel Default meters 880 Output 12 880T Output 12 840T Output 8 8i Mic 1 TH20 Telco Tx S...

Страница 14: ...2A FREQUENCY 50Hz 60Hz MIC LINE 1 2 3 4 1 2 3 4 LINE IN LINE OUT LINE OUT 5 6 7 8 5 6 7 8 LINK IN LINK OUT RS 232 CONTROL STATUS A B PC LAN TELCO LINE SET 1 10 11 2 3 4 5 6 7 8 9 Converge Pro 8i Rear...

Страница 15: ...roducts or Power Over Ethernet PoE devices will result in severe equipment dam age RS 232 Serial Port 7 Female DB9 connector for connecting to a laptop computer or remote control serial devices such a...

Страница 16: ...aker 4 16 An internal four channel 35 watt per channel amplifier 13 Speaker Connection For external speakers 70v or 100v system An internal four channel 35 watt per channel amplifier NOTE The Telco Se...

Страница 17: ...site in the conference should use echo cancellation There are several factors that contribute to poor echo cancellation These include Poor room acoustics High reverberation High noise Rapidly changing...

Страница 18: ...d noise within the vocal range on each mic input Unlike other noise cancelling devices Converge Pro does not simply gate audio off when a mic input drops below a specified level ClearOne s noise cance...

Страница 19: ...requencies above or below a given point and attenuate them while others allow you to attenuate specific frequencies Filters are also excellent for use in cancelling frequency ranges that cannot be tra...

Страница 20: ...hift vs a frequency producing a straight line results in constant time delay for all frequencies within the passband The linear phase shift reproduces a near perfect step response with no overshoot or...

Страница 21: ...frequency before full blown feedback arises Identifies multiple resonance frequencies simultaneously More precisely places the filter that stops the ringing noise The placement of the filter is accur...

Страница 22: ...outes it to the matrix via a second set of filters AGC ALC and auto mixing functions The settings of the filters AGC ALC and auto mixing functions mirror the setting of the primary audio path with ech...

Страница 23: ...thin the same group that are not chairman override enabled Adaptive Ambient On or Off When enabled the ambient level used to calculate gating is based on the room s actual noise floor integrated over...

Страница 24: ...communications difficult The more an the automatic mixer can prevent false activation of microphones by signals other then local talkers the higher the clarity of the audio Celling Microphones Figure...

Страница 25: ...erge Pro devices have a variety of automixing functions that are implemented on a per channel basis and across the entire auto mixer These functions are described on the following pages Each Converge...

Страница 26: ...te the microphone The ambient audio level can be specified or the adaptive ambient mode can be turned on In this case as the ambient room level changes the audio level required to activate a microphon...

Страница 27: ...icrophones after the first mic is gated on Last Mic mode Last Mic 1 8 Off Keeps the last gated microphone or one Mic 1 8 on when no mics are providing a gating input Gate Ratio Adjust 0 to 50dB Specif...

Страница 28: ...t below Figure 6 1 shows the default Converge Pro routing Figure 6 1 Inputs Mic line inputs The mic line inputs are located on the rear panel terminal blocks Both gated nongated and gated pre AEC inpu...

Страница 29: ...n the first unit is needed as a reference for mics on units 2 3 and 4 so that the echo canceller cancels the appropriate audio This is accomplished by selecting the appropriate PA Adaptive EC referenc...

Страница 30: ...PEQ CD Hom Bessel Cross Butterworth Linkwitz Riley Figure 6 3 Faders There are four assignable fader channels in the Converge Pro 880 880T 8i 840T Faders are a way to pre mix a number of input channel...

Страница 31: ...of the Converge Pro unit RS 232 external control devices logic in out and contact closure Ethernet or the ClearOne Tabletop Controller You can also create macros which can run multiple presets These o...

Страница 32: ...digital mix minus bus allows audio routing to and from any destination on the expansion bus It contains 18 independent digital audio buses and six PA Adapt echo cancellation reference buses Each audio...

Страница 33: ...refer ence input for PA Adaptive Mode Connecting To The Expansion Bus Each Converge Pro comes standard with one expansion bus cable The maximum cable distance allowed between any two Converge Pro unit...

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Страница 35: ...udio source enhancing the training experience All speakers can be optimized to produce full fidelity audio by programming the Converge Pros parametric equalizers and filters accordingly Typical distan...

Страница 36: ...capabilities In this scenario a Converge Pro TH20 is used for bringing in phone line audio and a video codec is used for video conferencing The Converge Pro 880 allows you to integrate both simultane...

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Страница 39: ...n Control AGC Automatically increases or decreases audio gain to maintain a consistent audio level Automatic Gating Automatically gates microphones on or off based on input levels and other parameters...

Страница 40: ...and optionally local program material Expansion bus Consists of two RJ 45 connectors on the rear panel of the Converge Pro 880 840T An expansion bus allows multiple Converge Pro units to be networked...

Страница 41: ...the last activated mic gated on until another mic input gates on Macro A series of user created instructions stored within the unit which can be executed from an RS 232 command or contact closure Mac...

Страница 42: ...phase angle 180 to 180 degrees vs frequency 20Hz to 20kHz on a logarithmic scale Pink Noise An audio test signal containing all the frequencies in a given audio spectrum with equal energy in each oct...

Страница 43: ...cancellation stage Acts only on voice signals Does not pull up the noise floor during periods of no signal Table View Displays the numerical values of the filter parameters for all nodes of the activ...

Страница 44: ...ClearOne Communications Inc 5225 Wiley Post Way Suite 500 Salt Lake City UT 84116 www clearone com...

Страница 45: ...lications A maximum processing delay of four 4 milliseconds Management Improvements Integrated Ethernet and USB connections SNMP and HTML remote management agents with SMTP email alerts Web based user...

Страница 46: ...ser and control consoles Event scheduler Diagnostic console Simplified Configuration Software Drag drop A V and channel objects Selectable Console views Unit Matrix and Channel Expanded serial command...

Страница 47: ...emote management agents Web based customizable user and control consoles Event scheduler Diagnostic console Simplified Configuration Software Drag drop A V and channel objects Selectable Console views...

Страница 48: ...B connections SNMP and HTML remote management agents Web based customizable user and control consoles Event scheduler Diagnostic console Simplified Configuration Software Drag drop A V and channel obj...

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