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Re: Recording Dolphins

Subject: Re: Recording Dolphins
From: "Robb Nichols" robb_nichols
Date: Wed Jul 9, 2014 9:36 am ((PDT))
Be careful not to get too lost in the prospective technical    
limitations of all of this.  Yes; you'll have reflections not
only     from the sides, but also from the bottom and surface and
you'll have     random distances from the source.  All of these
will make it pretty     impractical to measure source level
amplitude to any reasonable     degree of resolution.  Yes; you
may loose some high-frequency     information, limited by the
sampling rate of your A/D conversion.      But what are you
trying to do?  How will your recordings be used?      It may well
be that you don't need the resolution that you'll get     with
any given system anyway, or that there are limitations in the    
accuracy of your measurements beyond those of the hydrophone or
sound interface.  If you're just trying to detect certain sounds
and     perhaps correlate those sounds with certain behaviors, 
you may not     even need 192KHz.

What will you use for a preamp?

The lapel hydrophone concept could work.  Wireless is probably
not     an option because radio signals are grounded out in
water, but you     could potentially buy or build a recording
device that could be     attached to the subject.  Again though,
first you have to identify     your goals.  Perhaps you already
know exactly what you need, but you     haven't told us.

Regards, Robb

ps.  If anybody has an interest in having one of these Reson 4013
hydrophones, I have one that I would sell really cheap.  It
appears     to be damaged because it has had a recent calibration
from the US     Navy and HF response was limited to around 70KHz.
I think these     things cost about a thousand dollars now and
the calibration is     worth about another $500.  As it is not
performing to spec, I'd sell     it for $250.
Tue         Jul 8, 2014 8:09 pm (PDT) . Posted by:
>                   Thanks for the help and recommendations, the
work will be done in pools so we will have reflections off the
sides. Is there a way to mitigate that problem ? i guess a lapel
hydrophone with a wireless transmitter would be out of the      

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