CONFERENCE SYSTEM DESIGN
CONFERENCE SYSTEM DESIGN
Good audio or video conferencing is more than acoustic echo cancellation. Before installing the EF2241, you should consider how your whole conference system will work together. The goals of conference system design are the following:
•Transmit intelligible speech
•Reproduce received speech intelligibly
•Prevent echoes
•Interface properly with transmission equipment
•High quality program audio
•Intelligible sound reinforcement (if needed)
Noise and Reverberation
Consider Room Gain
Intelligibility can be affected by noise and reverberation. Noise comes from various sources such as HVAC, computers, projectors, or traffic. Some ways to improve the Signal to Noise Ratio (SNR) in your system include placing microphones closer to the talkers, using electronic noise cancellation, and applying acoustical treatments. The EF2241 is a great way to reduce noise in your system and improve the SNR. Poly- com’s patent pending noise cancellation algorithm, included in the EF2241, removes up to 10 dB of ambient background noise and improves perceived quality as well as intelligibility.
Reverberation in a conference system can reduce intelligibility in a room. To reduce reverberation and increase intelligibility, use directional microphone and loudspeak- ers, place microphones closer to the talker, and use acoustical treatment.
When planning your conferencing system, you should also consider the room gain that will occur as a result of your microphone and loudspeaker placement. Room gain refers to the relative level of the audio going to your amplifier (remote end speech or telephone speech) and the level of this audio being picked up by the microphone. We recommend a room gain of 0 dB or less for the best results. But for difficult acoustic environments, the EF2241, as well as any of the EF products, can handle up to 10 dB room gain, which means that it offers great flexibility in your conference system design.
To help you measure room gain, the EF2241 includes a room gain detector. You should check your room gain after you have set up the EF2241.
A
AEC
B
Room Gain = 20 log (B/A)
Figure 29. Room Gain.
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