Specifications

Audio Plug-Ins Guide336
At the same time, DINR also creates a model of
what the non-noise audio signal looks like.
DINR then attempts to pull apart these two
models, separating the bad from the good—the
noise from the desired audio. The noise portion
can then be reduced or eliminated.
The noise reduction itself is achieved through
the use of multiple downward expanders. The
threshold of these expanders is set so that the
noise signal will fall below them and be de-
creased while the desired audio signal will re-
main above them, untouched.
The Contour Line
Once the signal level has fallen below the speci-
fied Contour Line (which represents BNR’s
threshold), the downward expanders are acti-
vated and decrease the gain of the signal as its
level falls. Over five hundred individual down-
ward expanders are used linearly across the au-
dio spectrum to reduce the effects of unwanted
noise.
Psychoacoustic Effects of Noise Reduction
One of the psychoacoustic effects associated
with broadband noise reduction is that listeners
often perceive the loss of noise as a loss of high
frequencies. This occurs because the noise in the
higher frequency ranges fools the ear into think-
ing the original signal has a great deal of energy
in that range. Consequently, when the noise is
removed it feels as if there has been a loss of
high-frequency signal. DINR’s High-Shelf EQ is
useful for compensating for this effect. See
“High-Shelf EQ” on page 338.
Limitations of Noise Reduction
It is important to understand that there is a cer-
tain amount of trade-off inherent in any type of
noise reduction system. Implementing noise re-
duction means that you have to choose the best
balance between the following three things:
 The amount of noise removed from the signal
 The amount of signal removed from the signal
 The number of artifacts added to the signal
DINR gives you a considerable amount of con-
trol over the above three elements, and lets you
maximize noise reduction while minimizing sig-
nal loss and artifact generation. However, as
powerful as it is, DINR does have limitations. In
particular, there are two instances in which
DINR may not yield significant results:
 Cases in which the noise components of the
audio are so prominent that they obscure the ac-
tual signal components of the audio.
 Cases in which the noise amplitude of a 24-bit
file is less than –96 dB. DINR is not designed to
recognize noise that is lower than this level.
BNR Spectral Graph
The BNR Spectral Graph displays the noise sig-
nature and the editable noise Contour Line. The
Spectral Graph’s horizontal axis shows fre-
quency, which is displayed in Hertz, from 0 Hz
to one-half the current audio file’s sample rate.
The Spectral Graph’s vertical axis shows ampli-
tude, which is displayed in dB, from 0 dB to
–144 dB (below full-scale output of the audio).