Its been a while since I tinkered with Hydrophones, but last year I was quite
busy and documented most of the work via my blog:-
http://urlme.net/blog
There you will find a few different hydrophone examples:
Including the Construction Guides
- http://www.urlme.net/blog/?page_id=435
and 2nd part - http://www.urlme.net/blog/?page_id=456
This, http://www.urlme.net/blog/?p=380 Snows the various DIY hydrophones ive
made.
An electret mic covered with a thin layer of silicone will work underwater.
Polymer electret hydrophones:-
http://www.urlme.net/blog/?p=478
PVDF: http://www.urlme.net/blog/?p=498
My best advise would be to buy one from Aquarian Audio.
BR,
Mike.
--- In "jasonpudd" <> wrote:
>
> Patrick,
>
> From a practical perspective only, I am not the best person to ask
> technically about sound engineering but maybe someone else is in the group.
> If you used an air filled enclosure like this where I am from (British
> Columbia) you would have considerable build-up of condensation. This is
> caused by the colder temperature of the water in relation to the ambient
> above water. You may develop some problems with the unit due to this. If
> you had a small leak, even a drop, and this went un-noticed even for a short
> time, this would cause considerable corrosion from the salt water. Up here
> we pack our underwater stobe connections with silicon to stop this from
> happening and shorting our the contacts and causing corrosion. This works
> really well. The same problem happens in other climates with cold water
> temperatures.
>
> Jason
>
> --- In ". m u r m e r ." <murmer@> wrote:
> >
> > and while i'm out of lurk mode...
> >
> > i posted this question to the phonography list, but got no response, so
> > i thought i'd try here. any thoughts about this?
> >
> > i've been fiddling with building a simple hydrophone for awhile now.
> > i'd made several attempts with hollow cavities filled with vaseline,
> > poster tack, oil, or nothing. i'd read that a hydrophone ought to be
> > filled with oil, something about it having a similar density to water
> > and therefore letting the soundwaves travel through the cavity to the
> > piezo inside. working with oil is messy, however, and it's very
> > difficult to reliably seal the cavity without any air bubbles inside. i
> > managed one though, but i also had an identical one which i'd sealed
> > with an empty cavity. i compared them, and both work great, and sound
> > remarkably similar, if not identical. so what i wonder is: why do i
> > think the cavity needs to be full of oil? what does that provide that
> > my empty one does not have? anyone have any insight?
> >
> > best,
> > patrick
> >
> > --
> >
> > ||| www.murmerings.com |||
> >
>
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