Subject: Re: [linux-audio-user] recording bats?
From: Andres Cabrera (andres_AT_geminiflux.com)
Date: Sun Nov 14 2004 - 20:15:08 EET
Hi,
Sorry for the late chime in... There's something else that comes to
mind, which is the anti-aliasing filters. In my soundcard (Echo Mona
Laptop) which supports 96Khz sample rate, I analyzed white noise and
there seemed to be a low pass filter starting at around 20kHz, rolling
down all the way to the max frecuency 48kHz, so most energy above 35kHz
was captured pretty low.
It could have been the way the white noise was generated, or it might
have been a playback thing, but there's still always an anti-alias
filter on any adc and it probably starts around 20kHz.
Andres
Mark Knecht wrote:
> What an amazingly silly (and fun!) thread...
>
> Well, obviously you're going to need a tried and true 'Bat Detector Pre-amp'...
>
> http://home.kabelfoon.nl/~bertrik/bat/preamps.htm
>
> What it appears he did was to use an audio range microphone and then
> tune the preamp to only amplify very high audio frequencies. I.e. -
> build a 100KHz pream with a high-pass filter at 30-40KHz...
>
> I didn't think you could have paid me to participate in this one... ;-)
>
> - Mark
>
>
> On Tue, 9 Nov 2004 16:26:11 -0500, Eric Dantan Rzewnicki
> <rzewnickie_AT_rfa.org> wrote:
>
>>On Tue, Nov 09, 2004 at 11:58:54AM -0800, Erik Steffl wrote:
>>
>>>mik wrote:
>>>
>>>>a certain jonathan segel <jsegel_AT_magneticmotorworks.com> wrote:
>>>>
>>>>>if you do end up recording bats, and slowing them into audio range, i
>>>>>for one would like to hear the files!
>>>>
>>>>http://www.partnersinrhyme.com/soundfx/batsounds.shtml
>>>
>>> you (original poster, I don't have the first post anymore) might also
>>>consider other animals - small rodents, cats. Cats hear up to about
>>>60kHz (that's what I remember, even if it's not the right number they
>>>hear a lot higher frequencies than we do), it was explained in the book
>>>I read that that's what they need to be able to hear the small rodents
>>>(so I guess small rodents emit sounds up to about 60kHz), plus cats use
>>>higher frequencies to communicate among themselves (that's why you only
>>>hear them doing the meow sounds when they are around humans).
>>
>>Ah!! very, very interesting. We have 4 cats. Communication above our
>>hearing range would explain alot about how they all seem to notice some
>>things at the same time and other collective behavior. And here I was
>>thinking they were telepathic. I'm glad I asked my original question. :)
>>
>>-Eric Rz.
>>
>
>
>
>
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