Technical Description of TANDBERG 8000 with software version E3/B8
D12008 Rev. 11
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4.5.4
Acoustic Echo Cancellers
Acoustic echo cancelling is provided on Mic in 1-3 and Audio in 4. Each of these inputs has a
dedicated acoustic echo canceller. With a separate echo canceller per microphone, the echo
cancelling is vastly improved compared to using one common canceller for all microphones.
•
Echo cancelling tail length lowest frequency sub band 340 ms.
•
Echo cancelling tail length highest frequency sub band 250 ms.
•
Max acoustic echo cancellation 70 dB.
If an external echo canceller is used, the internal echo cancelling function should be switched
off for the respective audio input.
4.5.4.1
Adjusting the Acoustic Echo Cancellers
The TANDBERG 8000 has the ability to manually adjust the echo cancellers in two ways to
obtain the best performance for rooms with special acoustic environments; room
size
and
motion
, each controlled by a 0-15 slidebar placed under the echo control menu. Each slidebar
defines one common setting for all the acoustic echo cancellers in a system.
When adjusting these settings, please remember that in a video conference between system A
and system B, any echo problem on system A will be experienced by the users of system B and
vice versa.
Room size:
For optimum performance, this setting should be adjusted when the system is installed in a new
room.
This setting allows optimization of the echo canceller to the acoustic size of the room where the
system is placed. The setting should reflect the acoustic size of the room; two physically equal
sized rooms may require different settings, depending on the materials in walls, floor etc. If the
materials are hard (windows/metal etc.), the appropriate setting is higher; if the materials are
soft (carpets/curtains etc.), the appropriate setting is lower.
Correct setting of the room size parameter will lead to significantly increased echo canceller
performance. Adjust the setting if one of two symptoms occurs:
1) There is still some residual echo after a long period of training (audio from the
loudspeaker, but no talking in the room where the system reside); Increase the room size
setting.
2) The system adapts slowly to acoustic changes in the room (door opens, persons
moving etc.); Decrease the room size setting.
Please note that the system will have to readapt each time the room size setting is changed.
Motion:
If the system suffers from echo caused by heavy movements in the room, for example people
moving close to the loudspeaker and/or microphone; increasing this setting (i.e. number next to
slidebar) may reduce the problem.
By increasing this setting, limited voice switching is introduced in addition to the echo
cancellation; the higher the setting, the more voice switching is introduced. Therefore, a too high
setting may result in clipped words etc. during double talk situations.
