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Re: Recording Dolphins

Subject: Re: Recording Dolphins
From: madl74
Date: Wed Jul 9, 2014 2:54 am ((PDT))
 [naturerecordists] writes: 

> the hydrophone i have is a Teledyne Reson TC 4013 TC 4013 | Teledyne Reson 

I've had a look at the specs, and it is essentially a high impedance mic at 
audio frequencies. Going into a standard audio input, most of the audio 
spectrum will be very low level. I've looked at their pre-amp card: 

I'm not sure of their definitions, but the "Seastate zero" is only about 
20dB above the mic noise, so a 16 bit recording will be more than enough. A 
pool is likely to be very noisy in comparison, including pumps and filters. 

> 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 question.

Wireless won't work underwater. You could try a mini recorder in a 
waterproof case and leave it running. Does a dolphin call through its 
blowhole or through the skin? If the mic can be mounted near the source it 
would greatly reduce noise but also responses from other dolphins. 

The pool noise will come from single echoes and also general reverberation 
which is worse. You can't do much about echoes, especially from the surface, 
but you could try hanging blankets over the walls of the pool to act as 
absorbers. Even a small area of absorber may reduce the general 
reverberation if that is bad. 

David Brinicombe 

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