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To download a copy of the instructions on how to build an inexpensive hydrophone/preamp using a piezo speaker from a "singing greeting card" click - Hydrophone plans
And here is a setup that Yoshiro Sumiya did in concert with a video periscope in his Thor Seawolf...
I have been interested in building the "piezo hydrophone" but where does one get a piezo speaker (besides a singing greeting card). I might already have one; in that case could someone tell me what exactly a piezo speaker is?
They are available in electronic shops. Basically a flat brass disk with a ceramic centre. Good for underwater applications because they are "high impedance devices" unlike say a loudspeaker and not expensive. If you really want to know everything about them try this website]http://www.morganelectroceramics.com/[/url]
I have also developed a self powered Pinger which when used in conjunction with a hydrophone and amplifier (Loughborough design or similar) has been used by a number of sub modellers in th UK and elsewhere to prevent the loss of their submarines. It was reviewed in the October 2003 Issue of Marine Modelling International. For more details see my website]http://www.rdforrest.freeserve.co.uk/[/url]
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