User`s manual

Page 26
Using the NF575 Plug-In
The NF575 Noise Filter is a specially design set of algorithms used to remove
noise (but not music!) from the audio signal. The following sections cover basic
operations of the algorithms in the NF575 Noise Filter, provide a more in depth
description of some of the features of the NF575, and outline some applications
of the NF575 plug-in.
Basics
Filters can be broken down into 4 general categories - high pass, low pass, band
stop (notch), and band pass.
High Pass Filter (HPF)
High pass lters remove signals below the selected
frequency, and pass the signals above the selected
frequency unaffected (hence the term high pass). High
pass lters have a slope measured in the amount of
signal reduction (in dB) per frequency octave. Typically
these values are in multiples of 6 dB / Oct. At the exact
selected frequency of the high pass lter the signal
reduction is usually - 3dB, however this can change based
on lter design.
A high pass lter is useful for removing low frequency
rumble, unwanted vocal plosives, and dc offsets.
Low Pass Filter (LPF)
Low pass lters remove signals above the selected
frequency, and pass the signals below the selected
frequency unaffected (hence the term low pass). Low
pass lters have a slope measured in the amount of
signal reduction (in dB) per frequency octave. Typically
these values are in multiples of 6 dB / Oct. At the exact
selected frequency of the low pass lter the signal
reduction is usually - 3dB, however this can change based
on lter design.
A low pass lter is useful for background noise such as tape
hiss, waterfalls and general ambient background noise.
FREQUENCY
dB
FREQUENCY
dB