Thanks to everyone for the suggestions on the high-pass filter.
I think I need to explain my problem better. I put the mic on my
roof to detect the flight calls made by migrating birds,. The calls
are characteristically short and high pitched. I want to set the
gain on my system as high as possible so I can get the maximum
sensitivity and record calls that are weaker and/or made by more
distant birds. The large amount of low frequency noise in my area
increases the total sound level so high that clipping is sometimes a
problem when I set the gain high. The calls I'm interested in are
all > 2000 Hz, so by filtering the input I could get rid of a lot the
noise (without affecting the bird calls) and therefore be able to
push the gain higher. For this project I'm not looking for a nice
"natural sound" -- just interpretable data.
I monitor the skies from sunset to sunrise (9-10 h) so the sound
files I collect are huge (>1GB) . I use specialized software
(www.oldbird.org) to extract the flight calls of the birds. That
step seems to work ok even with the noisy recordings.
The Shure filter Dan suggested will provide some help and I'm going
to get one to try in the short run. But, in the long run I think I
will try to build a filter. The site Phil pointed out seems like a good st=
art.
David
At 11:22 PM 8/15/2007, you wrote:
>Hello David,
>
>I think that you can use the sound program Audacity to filter sound files.
>Look at the FFT filter under effects menu.
>
>Everett
>
>
>
>At 06:28 PM 8/14/2007, David Martin wrote:
>
> >I've had it working for three nights now. I'm getting decent
> >signals, but I'd like to use as much gain as possible. However, low
> >frequency noise from traffic, trains, and and aircraft can overload
> >the system. (I'm a mile from relatively busy railroad tracks and 10
> >miles from a busy airport). I am just monitoring songbird flight
> >calls and only need to record above 2000 Hz, so I should be able to
> >greatly reduce the problem with a high-pass filter. Can anyone
> >suggest a filter that might work or does anyone know of a plan for
> >building one?
> >
> >David
> >
> >
> >
> >
> >"While a picture is worth a thousand words, a
> >sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause
> >
> >Yahoo! Groups Links
> >
> >
> >
>
>
>
>
>"While a picture is worth a thousand words, a
>sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause
>
>Yahoo! Groups Links
>
>
>
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