[CM] noise reduction with snd

Bill Schottstaedt bil@ccrma.Stanford.EDU
Fri, 23 Aug 2002 04:33:04 -0700

>  As I am a complete newbie in the field, I don't really know what "apply both a lowpath and a highpath to the
> original signal" means.'

For a speech signal, I'd start with 500 Hz to 4000 Hz, then narrow or
widen depending on the results -- hiss is the "high" side, rumbles
are the "low" side.  Perhaps the quickest way to check in Snd
would be to open the controls panel, draw the envelope in the
filter graph (1.0 = srate/2 here), so if your srate was 44.1KHz,
you'd want to zero out 0 to (ca.) .02, then 1.0 (y) to .2 (x),
then back down to 0 for the rest, then set the filter toggle
button (on the far right) and push "play" (or "apply").  If you find
settings you like, you can set up a loop through all your
recordings, calling filter-sound on each (using Snd as a
script engine essentially).

(To force the filter graph to appear, after open controls, drag
the lower pane upwards to get all of the panel displayed -- I
never did decide what the "right thing" was here).