Specifications

Chapter 8: DINR 73
Center Frequency Sets the fundamental fre-
quency of the Harmonic filter. Though the
Learn function automatically sets the center fre-
quency to the fundamental frequency of the
learned noise, this parameter can also be manu-
ally edited. The other notches in the harmonic
filter are automatically set to the related har-
monic frequencies.
Cut Level Determines the depth of the notches
within the Harmonic Filter. This allows you to
specify the amount of hum removal that takes
place when the signal falls below the threshold.
Higher dB settings result in deeper notch filters
and more noise reduction. Lower dB settings
produce fewer undesired alterations of the au-
dio. A cut level of 0 dB applies no harmonic fil-
tering. A cut level of –∞ applies maximum hum
removal.
Threshold Sets the signal level at which the har-
monic filtering occurs. If the input signal level is
below the threshold, the harmonic filter is acti-
vated and hum is reduced. When the signal
level rises above the threshold, the harmonic fil-
ter is bypassed, since loud signals psychoacous-
tically mask the audibility of noise components.
Setting the threshold to 0 dB (its highest level)
will cause the harmonic filter to always be ac-
tive. For optimum hum removal and a mini-
mum of artifact generation, adjust the Thresh-
old so that it is just above the noise level.
Attack Controls how long it takes the Harmonic
Filter to reach its full effect once the signal has
fallen below the threshold you have set. The de-
fault attack value is 15 ms.
Release Controls how long it takes the Har-
monic Filter to switch off once the signal has in-
creased above the threshold (determined by
your Threshold setting). The default release
value is 15 ms.
Learn Analyzes the selected audio and automat-
ically sets the center frequencies of the filters for
maximum hum removal. The Learn function
saves you the trouble of manually sweeping
through the frequency controls in order to find
the appropriate fundamental center frequency
for hum removal. There are two Learn modes:
Learn First Audio mode and Learn Last Audio
mode.
Learn First Audio Mode The default Learn mode.
It is designed for use with audio that has an
identifiable noise-only section that you can lo-
cate and pre-select. To use this mode, locate and
select the noise-only portion of the audio, click
the Learn button, start Pro Tools playback, and
the Hum Removal plug-in will set an appropri-
ate fundamental center frequency for hum re-
moval based on the first 16 milliseconds of au-
dio playback. First Audio Learn mode can be
thought of as a trigger-learn mode, since noise
capturing is triggered by the first audio that
DINR receives.
Learn Last Audio Mode Activated by Option-
clicking (Macintosh) or Alt-clicking (Windows)
the Learn button. It is designed to allow you to
locate and identify a segment of noise on-the-fly
as you listen to audio playback. In this mode,
you first Option-click (Macintosh) or Alt-click
(Windows) the Learn button, then initiate audio
playback. When you hear the portion of audio
that contains the noise you want to identify and
remove, click the Learn button a second time.
The Hum Removal plug-in will set an appropri-
ate fundamental center frequency for hum re-
moval based on the last 16 milliseconds of audio
playback.
Center Frequency