Polycom C16 - Manual (Page 476)

Design Guide for the Polycom SoundStructure C16, C12, C8, and SR12
B - 14
200 msec for larger rooms. As shown in the following figure, if the room is
lively, the length of an echo path may be longer than expected making the
room appear acoustically larger than it is physically.
Transmission Delay
In all communication networks, there is a combination of processing latency
and network latency that delays when the local signal is heard in the remote
room and conversely when the remote signal is heard in the local room. There
have been numerous studies that have shown that when delay is added to an
echo, the perceived communication impairment caused by the echo is
increased. Processing latency is due to the selection of algorithms, the speed
of the underlying processors, the implementation of the algorithms, and how
the audio is collected from the analog-to-digital converter and also sent to the
digital-to-audio converter in a digital system. In some cases, such as in video
conferencing systems, delay may be intentionally added to the audio signal to
compensate for the delays inherent with video signal in order to maintain
audio and video lip synchronization. Network transmission delay is limited
by the speed of electrons (or the speed of light with satellite and microwave
transmission) in a network and any other processing or data handling that
Direct
1st Reflection
2nd Reflection
3rd Reflection
4th Reflection
5th reflection
Microphone
Loudspeaker