Upgrade Manual

Appendix A: "Audio Plugins" 81
Line Frequency:
Set to the local power frequency. USA and Canada uses
60 Hz.
Filters:
Choose the active notch filters, among the lowest six harmonics of
power hum. Each filter is a tenth-octave wide.
Sometimes hum is "pure" and sometimes hum contains upper-frequency
harmonics.
Though these notch filters are narrow, they still affect your audio to some
extent, so it is best to use the smallest number of filters necessary to do the
job.
For instance, if there is no noticeable hum above the 180 Hz range, the
Harmonic 4, 5 and 6 filters are not necessary, and should be disabled.
Try a short Preview with only the first filter enabled. If hum is audible in the
Preview, enable the second filter and Preview again. Keep Previewing and
enabling filters, until the hum is gone.