Cedar DNS3000, Manual, Page: 16 / 44

CEDAR DNS3000 dialogue noise suppressor
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Case 2: Suppressing tape hiss
The DNS3000 can suppress the tape hiss that mars many older recordings. It will also improve
the signal/noise ratio of dialogue tapes that have been poorly copied as well as those that are
many generations old.
First, identify the frequency range(s) in which the noise lies.
You should follow the procedure laid down in case 1 to determine the range(s) in which the
problem lies. For most instances of tape hiss, you will find that the Mid+High ranges are most
appropriate. In a few cases you may find that the High range alone is most suitable. It is not as
common to require suppression in the Low range because hiss is usually less prominent at lower
frequencies, and it may also be masked by the genuine audio in the range.
Second, optimise the Level control.
To determine the correct Level, you should again follow the procedure described in case 1.
Third, refine the Band Gain controls for optimum suppression.
As in case 1, you should start with all six Band Gain controls at 0dB. You should then increase
and decrease each control individually to find the bands that contribute most hiss to the signal.
Because tape hiss often exhibits a ‘white’ profile at Mid and High frequencies, you may find that
satisfactory results are achieved with the Band Gain controls set in a horizontal line.
However, hiss is generally less annoying at very high audio frequencies. Consequently, you may
be able to reduce the amount of processing in the uppermost bands. This will help to ensure
that any low amplitude signal components lying at high frequencies (which provide much of the
‘air’, ‘ambience’ or ‘life’ in a signal) are passed with little or no attenuation.
The final configuration may look like this: