notchf

Short:        Filter mains hum off 8SVX samples, V1.1
Author:       wnoeker@t-online.de (Wilhelm Noeker)
Uploader:     wnoeker t-online de (Wilhelm Noeker)
Type:         mus/misc
Architecture: m68k-amigaos

A notch filter (that's what "notchf" stands for) is a band reject filter 
with an extremely small bandwidth.  It can remove noise at a known single 
frequency (e. g. mains hum at 50 or 60 Hz) from a sound recording.

"notchf" can apply several filters in one pass (useful for oscillations 
with upper harmonics, e. g. at 50, 100, 150 Hz etc.) and provides control 
over the sharpness of the notches (to make hitting the right frequencies 
a little easier).  Try this on the included example IFF sound:

  notchf -f0.015 -f0.030 -f0.045 sspa.iff test.iff

New since V1.0: Better information on the bandwidth of the filters, in 
the docs *and* at run-time.

"notchf" is Freeware, C source is included.