VOICECRAFTER
TM
CONFIGURATION
6
4.3.2 ERLE
ERLE (Echo Return Loss
Enhancement) is a measurement of the
Voicecrafters ability to build an echo
canceling model of the room. The
ERLE is actually a snapshot
measurement taken at the end of a
Configuration Train cycle. The
Voicecrafter calculates ERLE by taking
what is received by the echo canceller
(EC_Si) and subtracting what is sent
out of the echo canceller (EC_So)*.
The formula is (EC_Si - EC_So =
ERLE). The ERLE should be 8dB or
greater. If the ERLE is 7dB or less, the
Echo canceller will not be able to adapt
quickly to changes in the conference
environment.
(*EC_So - the amount of signal fed out
of the echo canceller to Codec Out and
Aux Out.)
4.4 PROBLEMS WITH TRAINING
If the Voicecrafter can’t achieve an
AERL /-2dB of target, the target
may need to be raised or lowered
depending on the room. Example: A
large room, which produces excessive
loudspeaker gain and echo after
training, may require the AERL target be
increased. However, a small room,
which produces insufficient loudspeaker
gain, may require the AERL target be
decreased. After adjusting the AERL
target, the Voicecrafter must again be
put through a Configuration Train cycle.
The room should be quiet during any
training cycle. An EC_Si of less than
-35dB is desired for an accurate training
cycle. This can be measured by
selecting the DSP AVE button on either
the ACOUSTIC, NETWORK, or
DIAGNOSTIC screens. Use F2
⇐
or
F3
⇒
to display EC_Si.
Placement of microphones in relation to
speakers is essential for proper training
values. If a microphone is too close to a
speaker, the Voicecrafter may set
microphone or speaker gains to low,
which will affect the AERL. Microphone
default settings also play an important
part in determining AERL and ERLE
values. When connecting a microphone
mixer directly into a Voicecrafter, be
sure that Mic 2 is set for line level input.
The Mic 2 default gain will depend on
the output level of the microphone mixer
(see paragraph 6.3).
The loopback features, described in
paragraph 5.3.4, are excellent tools for
determining if your microphone gain
and speaker gain settings are correct.
If you talk through a microphone and
get a clear signal during a microphone
loopback, this is a good indication that
the microphone and speaker settings
are correct.
AERL and ERLE values can more
easily be achieved by properly adjusting
microphone gain settings, and by
paying attention to appropriate
microphone and speaker alignment.
4.5 MIX-MINUS
When a mixer is connected to both a
Voicecrafter and a local sound
reinforcement system, it is essential that
Voicecrafter output signal never be fed
back to the Voicecrafter input.
Therefore, the mixer must provide an
output to the local sound reinforcement
system, which includes all signals (near
end and far end). In addition, the mixer
must also provide an output to the
Voicecrafter, which includes only local
signals (near end). This is known as a
‘mix-minus’ output.
