Technical information

McDSP plug-ins
stop to band-pass. If the  lter frequency is then swept across its frequency
control range until it corresponds to a problematic noise frequency, and if
the Range control is set to a high value, this noise frequency will be boosted
by the band-pass  lter (instead of being cut by the band-stop  lter) and will
sound very loud – making the problem frequency very obvious.
Once you have identi ed this noise frequency, un-solo the notch  lter so that it
becomes a band-stop  lter, and it will remove this noise frequency. You should
adjust the Q control as tightly as possible to remove only the unwanted noise.
If there are additional noise frequencies present in the audio, you can repeat
this process for all the notches, or until all the audible noise frequencies have
been identi ed and removed.
Applications
Quite often, you will need to remove noises such as AC power hum. This has
a fundamental frequency of 50 Hz in the United Kingdom and 60 Hz in the
Figure A12.7
NF575 showing  lter
1 soloed so that it can
be swept to identify a
noise frequency.