Low frequency underwater speaker/transducer

Have you researched how the Navy does this?

The navy uses stuff like Terfenol-D and uses quite high frequencies. Terfenol-D is very expensive. I was thinking more like a conventional subwoofer speaker cone

Why not just use your Magick ??

hamilton

Take a weather-proof bullhorn style outdoor PA speaker, and attach a clear membrane onto the face. A THICK membrane. Take it underwater, and there ya go! The membrane will cycle at the rate you pump into the horn.

Wont get a lot of amplitude but water transfers sound a LOT better, so no nee for great amplitudes.

Dirk-

Someone at sci.physics.acoustics may have experience doing what you are trying.

I'd look at the Bruel & Kjaer website for acoustics equipment. If they have anything for underwater work, it may be the best you will find.

If you search the web for Underwater Speakers, you may find something a little cheaper.

Fred

Because binaural tones and neural patterned magnetic fields are not the correct technologies.

I need a far better coupling of energy to water than will be accomplished by putting a gas interface between them. Maybe some kind of linear actuator...

I doubt cheap, but Seismic surveys for oil and gas exploration use some sort of transducer to generate the vibrations. Or depending on exactly what you are trying to do, a few sticks of dynamite would work.

Dan

I just want to shake a few kg of jelly around at a few Hz

They make shake tables for vibration testing.

You might be able to copy their technology.

I was thinking along those lines but I really want low frequency audio. Maybe time to do a few experiments with linear power actuators

Piezo drives?

DB > I just want to shake a few kg of jelly around at a few Hz

Take up fast walking.

I do not know about what you may call cheap, but try various brands of wire-wound high power rheostats; the nickel in the wire appears to convert the current into sound. One can have a rather severe ultrasonic generator...

Lousy power and the damping of the liquid would make for low efficiency, i think.

Try something like one of these:

(Fane compression drivers.)

You may need to pull it apart and machine aways some of the top cover/coupler.

Don't worry about the high resonant frequency - this will change when you add the kgs of jelly !

You may need to jelly proof the diaphragm by the application of some kind of flexible coating.

If your jelly pond is deep you may need to equalise pressures behind the diaphragm.

What are you trying to do ?

Michael Kellett.

Why not use a cheap dc motor with an eccentric weight on its axis? Good for 0-300hz, and quite a bit of power.