On 06/02/2010 12:10 AM, Philipp wrote:
2) a very loud noise, possibly from some part of a laptop. To my
knowledge the recording was made in two takes, guitar and voice, on a
laptop with a cheap mic of some sort. The noise seems to be located
mainly somewhere around 12kHz, a region which seems to be important for
the clarity of the voice. Any attempts to just pull down with an eq
(4-band parametric for example is what I tried today) had a significant
impact on the voice.
have not tried on mp3s, but i think it would work on .wavs, assuming the
voice is dead center mono, no important instruments are dead center
mono, and the noise is uncorrelated, i.e. different on both channels.
convert the L/R signal into an M/S signal: M = L + R, S = L - R. plus
here means "mix", minus means "invert the phase of R and mix".
with luck, you will have voice and not much else in M, and the rest in
S. if the noise crept in after the voice recording, chances are it's
"stereo noise". if the original voice track was noisy, you lose.
if it indeed is "stereo noise", try to kill it in the side channel only
with aggressive notch filtering. the clarity of the voice should be
mostly unaffected, since it resides in M.
now reconvert back to L/R: L = M + S, R = M - S.
while you're at it, you can also play with the base width, by changing
the M:S ratio before converting back.
how well this trick works on mp3 depends largely on how well the stereo
information is preserved in the mp3 (joint stereo, discrete, or even
mono)...
this method is how naive karaoke filters work: eliminate center content.
another good way to accomplish this is to plug a stereo jack (that
carries unbalanced stereo) into a balanced line input. frequently seen
in the wild, usually unintended :-D
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