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Re: how best to connect a hydrophone to a laptop?

Subject: Re: how best to connect a hydrophone to a laptop?
From: Dave Mellinger <>
Date: Tue, 30 Dec 2003 12:50:50 -0800
>I want an inexpensive way to connect a hydrophone to a
 >PC such as to the RCA mic jack of a laptop or a PCMCIA
 >card. I will then write the software to read the
 >audio-in port. I want to read frequencies between 1 Hz
 >and 100 kHz and use my own software to read the input
 >port. I already have the FFT and other signal
 >processing completed.
 >Does this make sense? For example, isn't the typical
 >mic port build for the frequencies of the human audio
 >range or can it accept a wider range? If I need a
 >PCMCIA card or some other interface for the A/D then
 >which one would you recommend?
 Yes, the mic/line-in port on most sound cards has a maximum sampling rate
 of 48 kHz, so the maximum frequency it can capture is half that or less.
 Typically you see good frequency response up to 20-22 kHz.
 To get higher frequencies, you need a more specialized data acquisition
 card.  I've used National Instruments cards with success, specifically the
 DAQCard 6062-E, which is a PC card (PCMCIA card), and the PC6071-E, which
 is a PCI board.  These should give you single-channel input at the
 frequencies you need.
 You may also want to try out Ishmael, which can record sound onto disk
 according to a schedule you set up, display real-time spectrograms, detect
 calls, localize calls, and a host of other tasks.  It can interface to the
 above NI cards as well as some other cards.  It's freely available at
 <a  href=""; 
rel="nofollow"></a> .
 >Which hydrophone(s) do you recommend?
 I'd suggest looking at Joe Blue's hydrophone page.  You can find it via the
 "Equipment" link on the ASA Bioacoustics site,
 <a  href=""; 
rel="nofollow"></a> .
 Hope this helps,
 Dave Mellinger

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