At 05:35 PM 7/31/2010 +0300, you wrote:
>I just checked the hydrophones, there appear to be no problem at all with=
>them ..
>
>what makes me really skeptical is that only one of them picked the sound -=
>if it was something distant (like a radar) both of them should have picked=
>the sound..
>
>I tend to think the source was located really near the hydrophone.
>
>Just to note that after I buried them in the sand I used two small stones=
>to keep them in place - maybe that explains sth ?
First off, thinking RADAR may be the cause of the noise should be ruled
out... Radar operates at such high frequencies typically above 1000 Mhz
that it will never have enough energy at the audible frequencies to be of
any effect. This I know of for a fact which I will explain further down...
Secondly, broadcast radio stations will not affect transducers directly,
especially if they are submerged mainly for the same reasons as RADAR will=
not affect a transducer as radio stations operate at frequencies also way
above the audible frequency range... However, radio frequencies of some
broadcast station can cause problems with deck gear (electronics such as
recorders) however this is often simply remedied by using tiny ceramic or
silver mica capacitors of .01ufd and .001ufd to ground (shield) on both
legs of the lead bringing power to the unit in trouble as well as on
microphone and transducer leads...
How I know this? Fifteen years of working in an engineering lab co-located=
with a Marine Electronics shop that sold and serviced marine RADARS to most=
of the commercial fishing fleet as well as large yachts in Southern New
England. And our shops were located 2 blocks from radio station WCIB so we=
had plenty of experience dealing with such matters...
I'd say, if its not a leak as Robb suggests, then it has to be something in=
the sand next to the hydrophone, most likely a biological critter which the=
sands are loaded with... Another possibility is wave action moving the
stones holding the hydrophones in place... Waves move stones all the time,=
its how stones at the beach get the nice smooth rounded shape...
--
Thanks,
Mitch & Shadow...
http://www.4shared.com/dir/UTASxktL/wildlife.html
Shadow's area: http://www.4shared.com/dir/ecfWjyZb/Shadow.html
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