I have found this of use when making piezo mics
http://www.musicofsound.co.nz/blog/the-first-rule-of-contact-mic-club
Basically you want a custom 'preamp'. You don't actually need to amplify
the signal (piezos already give you signal on the order of volts), but you
need a much higher input impedance than typical audio gear. Otherwise the
inherent capacitance of the piezo disc itself will combine with a typical
50k=D9 input impedance to form a high-pass filter at around 200Hz, resultin=
g
in a 'tinny' sound. You could try a unity-gain op-amp buffer as a simple
preamp.
On Fri, Mar 15, 2019 at 7:16 AM
[naturerecordists] <> wrote:
>
>
> I thought this may be of interest.
>
> At the moment I'm working on a DIY hydrophone. I'll be using 21mm piezo
> electric transducers as "contact mics", which I'll be securing inside a
> home built enclosure - basically a length of 32mm plumbing tubing, with c=
ut
> down end caps glued at either end.
>
> I've uploaded some photos to the group website here (hopefully link shoul=
d
> work)
>
>
>
> https://groups.yahoo.com/neo/groups/naturerecordists/photos/albums/433813=
111/lightbox/260534497?orderBy=3Dordinal&sortOrder=3Dasc&photoFilter=3DALL#
>
> My recorder is an Olympus LS14, so I'm unsure whether it will need preamp
> or something for the piezo transducers to give a decent enough signal for=
a
> good recording level.
>
> Anything else I need to consider? If I fill the interior of the enclosure
> with epoxy resin to make it waterproof, will that impact on the signal fr=
om
> the transducers?
>
> Regards,
>
> Brian.
>
>
>
"While a picture is worth a thousand words, a
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.
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