rumble, motor-like sound. What frequency to set notch filter?

I'm trying ot clean up a WAV file that has a low sounding
rumble, motor-like 
sound, sort of up and down.  It's lower than the bass line.
I'm finding this
hard to describe in words.  I'm using the Gnome Wave Cleaner
and its got
a notch filter but I don't know what frequency to set it
for. I do know people
hear from about 20 Hz to 20,000 Hz, on a good day, so would
maybe 50 Hz
to 100 Hz would be a good start?
   
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On Mon, Apr 16, 2007 at 08:49:19AM -0500, millward wrote:
> I'm trying ot clean up a WAV file that has a low
sounding rumble, motor-like 
> sound, sort of up and down.  It's lower than the bass
line. I'm finding this
> hard to describe in words.

Can you post a small sample somewhere?

>  I'm using the Gnome Wave Cleaner and its got
> a notch filter but I don't know what frequency to set
it for. I do know people
> hear from about 20 Hz to 20,000 Hz, on a good day, so
would maybe 50 Hz
> to 100 Hz would be a good start?

IF you're lucky, it might be that the rumble really is
completely
lower than the bassline. In that case, I'd try a very steep
highpass
filter first.  Set it to just below the lowest fundamental
in the
bassline and see if that helps.

If the bassline is from a bass guitar, low E fundamental is
about 41
Hz and low B fundamental on a 5-string is about 31 Hz. 
(Handy chart
here: ht
tp://en.wikipedia.org/wiki/Piano_key_frequencies).

Typically most of the energy from a bass guitar is in the
first few
overtones, so you might also be able to apply some gradual
rolloff of
frequencies below about 80 Hz.

-- 

Paul Winkler
http://www.slinkp.com
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