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6.
AUDIO ALARM CALIBRATION PROCEDURE
This section contains a detailed description on setting the various audio warning/error detection
parameters.
Some of the audio alarm detection algorithms are dependent on the state of other audio alarm detectors.
For instance, the mono detection algorithm will not use periods of silence as determined by the silence
detection. For this reason, the following sequence should be used to calibrate the audio alarms. The items
in italics refer to menu items in the CEM. See section 7.10 for a complete description of the fault definition
menu items.
6.1.
CALIBRATE AUDIO SILENCE DETECTION
1. Supply the card with your plant's noisiest audio feed without any audio program material present. This
will be a baseline noise level to calibrate the silence detector.
2. Turn off all sources of errors in a Fault Condition and assign Audio Silence as the only error. Also,
make sure that you set the Fault Duration to a small number of frames so that you will see when the
error condition disappears.
3. Set the Silence Duration to 0.5 sec so that you can see the results of adjusting the Silence Level
parameter without getting confused with the detection time.
4. Adjust the audio Silence Level until the Fault Condition begins to go active. This will be the noise floor
level. Raise the Silence Level a few dB to make the detector insensitive to this noise level.
5. Set the Silence Duration to a time appropriate to your application. This should be set to a value longer
than your worst case acceptable quiet period.
6.2.
CALIBRATE AUDIO PHASE REVERSAL DETECTION
1. Supply the card with a stereo signal that has the phases reversed. Make sure that the material is
typical of normal content for this channel.
2. Turn off all sources of errors in a Fault Condition and assign Phase Reversal as the only error. Also,
make sure that you set the Fault Duration to a small number of frames so that you will see when the
error condition disappears.
3. Set the Phase Reversal Duration to 0.5 sec so that you can see the results of adjusting the Phase
Reversal Level without getting confused with the detection time.
4. Adjust the Phase Reversal Level so that the Fault Condition detects the phase reversal.
5. Set
the
Phase
Warning: Periods of silence (below the Silence Level) will extend this duration. In other words, periods
without
audio
Warning: Stereo material with long periods of dissimilar left/right content (i.e. music with plenty of
panning) may cause the phase reversal detector to fire. It is best to set the Phase Reversal Duration to
a value larger than what you would expect.
6.3.
CALIBRATE AUDIO MONO DETECTION
1. Supply the card with a stereo signal that originated from mono material and that has a large amount of
un-correlated noise added to each channel. This will allow you to set the Mono Threshold to a value
that will detect the mono condition in the presence of noise.
Warning: Make sure that the material is in-phase. Mono material will not be detected if it is out of
phase.
Gray background indicate un-implemented or un-tested features
Reversal
Duration
content
are
not
Revision 1.1.1
7735CEM Composite Encoder with Monitoring
to
a
time
period
included
in
the
7700 MultiFrame Manual
appropriate
to
your
phase
reversal
application.
detection.
7735CEM-13
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