the best solution is always to prevent wind effects on the mics by
proper protection.
the first effect is the creation of low frequency waves in your
files; in some cases you can just high-pass filter, but in other
cases the low frequency waves induce distortion on the other recorded signa=
ls.
If you have an overload limit of, say, + -1V, and your sounds peak at
+ - 0.6V, your recording is ok and you still have some headroom. Now
add a low frequency wave peaking at + - 0.1V that adds to the other
sounds: your levels will be -0.5 ... +0.7V on positive wind waves and
-0.7 ... +0.5 on negative waves. In this condition you are still
safe, your system is not pushed to the limits and normally you can
successfully HP filter.
but if the wind wave is stronger, say, + - 0.5, on positive wind
waves your signal will overload (+0.5 +0.6 =3D +1.1!) all positive
half-waves of your song; and on negative wind waves the negative
half-waves of your song will be overloaded.
You can still remove the low frequency waves, but at the end you'll
have your song asimetrically overloaded.
At this point the only viable solution is to accurately isolate the
overloaded waves and reconstruct them manually or by low-pass
filtering; in other terms you can only try to attenuate the harmonics
(distortion) created by the overloading.
Gianni
At 00.44 09/03/2006, you wrote:
>Hi there,
>
>Does anyone know of a piece of software that is able to filter out
>wind or background noise from bioacoustic recordings?
>
>Thanks,
>Natalie :)
>
>
>
>
>
>"Microphones are not ears,
>Loudspeakers are not birds,
>A listening room is not nature."
>Klas Strandberg
>Yahoo! Groups Links
>
>
>
>
>
>
>
>
>
>
>
>--
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--------------------------------------------------------------
Gianni Pavan
Email
Centro Interdisciplinare di Bioacustica e Ricerche Ambientali
Universita' degli Studi di Pavia
Via Taramelli 24, 27100 PAVIA, ITALIA
Tel +39-0382-987874
Fax +39-02-700-32921
Web http://www.unipv.it/cibra
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