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Re: Recording Dolphins

Subject: Re: Recording Dolphins
From: "Gianni Pavan" gpavan1960
Date: Tue Jul 8, 2014 5:20 pm ((PDT))
to record dolphin (ultra)sounds you have to take into account many
different things...

if you work in a pool at close distance you need a broadband hydrophone
with low sensitivity to avoid overloading its electronics with echolocation
pulses that are very short in time but very high in peak pressure. In such
situation you may receive the full bandwidth of the source that extends
beyond 96 kHz, however how much bandwidth you need depends on how detailed
you want to have the pulses, e.g. to evaluate spectral changes related with
different echolocation tasks.

if you work in open sea you need a higher sensitivity hydrophone with low
self-noise to maximize its sensitivity to pulses coming from a large
distance. In such situation the highest components of pulses are lost due
to high frequency absorption and in most cases 96kHz of bandwidth is enough
to receive and analyze echolocation pulses.

But there are few species that have most of their signal energy above
100kHz, e.g. harbor porpoises and few other species.
The equipment is always a compromise between different needs and different
technical constraints. e.g. if you need 200kHz bandwidth you need a very
small hydrophone but this also means reduced sensitivity and the need of
more electronic gain that may mean more noise and much lower signal to
noise ratio.

For very generic dolphin recordings a good compromise might be an
hydrophone going up to 80kHz and an AD board at 192kHz. This way you can
record most of the existing species, their social signals and also their
echolocation pulses.
But if you have very specific needs, then you need specific equipment.

Feel free to write me privately if you need more detailed info.


2014-07-08 15:29 GMT+02:00  [naturerecordists] <

> i have a Reson TC 4013 hydrophone that is supposed to extend to 170 kHz s=
> it should be ok at the source

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