Polycom EF2241 - Manual (Page 53)

C
ONFERENCE
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YSTEM
D
ESIGN
© Polycom, Inc. 49 V ORTEX EF2241 Reference Manual
C
ONFERENCE
S
YSTEM
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ESIGN
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
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.
Consider Room
Gain
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.
Figure 29. Room Gain.
AEC
A
B
Room Gain = 20 log (B/A)