CEDAR Duo – declickle and auto dehiss
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Auto dehiss tutorials
These Left/Right tutorials assume that the material exhibits virtually identical noise
characteristics in each channel. If it does not, you should follow these instructions but adjust
each channel independently to obtain satisfactory results.
Preparation
It is important that the audio presented to auto dehiss is free of clicks and crackle. This is
because these degradations will interfere with the dehissing process and prevent you from
reaching an optimal result. If necessary, you should pass the signal through the Duo declickle
processor or other CEDAR declick and decrackle processes before applying the auto dehisser.
Manual Mode (L-R channel mode selected)
Set the auto dehiss processor in MANL (manual) mode, and ensure that the MANL-OFF control is
in the MANL position. Now set the Level and LF Bias to zero, and the Attenuation to -40dB, and
follow the next three tutorials in sequence.
Level Tutorial
Your first task will be to find the most appropriate setting for the Level. This will be the biggest
influence on the quality of the processed signal.
Starting with the Level at zero and the Attenuation at -40dB, increase the value of the Level. At
first, you will notice very little happening. Next, you enter a region in which there may be noise
bursts and an artefact similar to noise pumping. Increase the Level further and these side-
effects will begin to disappear and, at some point determined by the nature of the signal, the
noise will decrease rapidly. Because the Attenuation is set to maximum, you will in all likelihood
now find the signal to be somewhat muffled.
The optimal value of the Level is approximately the crossover point between the noise artefacts
and the muffled sound.
There is a delay of a fraction of a second between adjusting the Level and hearing the effect at
the output.
LF Bias Tutorial
At this point, you may wish to modify the processor’s action to accommodate broadband noise
with differing frequency characteristics. Your Duo allows you to do this by accentuating or
suppressing the amount of noise identified at low+mid frequencies.
