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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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