The Radiation Pattern

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Ron Hubbard - 15 Jun 2004 00:35 GMT

Maybe someone can help answer a few questions for me.

A few years ago I had a little ultrasonic transducer that was
about an inch or less in diameter and made out of an aluminum can
with a thinner aluminum face. Unlike current transducers that has
a diaphragm, this transducer had a small ring of piezoelectric
material that was mounted directly on the inside center of the
transducer's face.

At about 20 to 22 kHz, I saw this transducer produce cavitation
in a glass of water from a few inches away. I liked that little
transducer but lost it sometime ago. Now I am thinking of building
another, but I am wondering just what kind of radiation pattern a
transducer like this can produce? Does sound come out as a beam or
does it spread? And compared to acoustical designs that have
diaphragms, how effective a radiator is this kind of transducer?

Any help would be appreciated.

Ron

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Wieslaw Bicz - 20 Jun 2004 17:06 GMT

>Maybe someone can help answer a few questions for me.
>
[quoted text clipped - 18 lines]
>
>

If the transducer have had a diameter of about 1 inch, and the wave
length is significantly longer (20kHz wave in water has about 3 inch
wavelength), radiation pattern was undependent on the shape of ceramics
almost spherical.

Transducer able to produce cavitation must probably be a sandwich type -
if this was not a special construction, that is not typical.

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Wieslaw Bicz

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Ron Hubbard - 24 Jun 2004 07:54 GMT

> >Maybe someone can help answer a few questions for me.
> >
[quoted text clipped - 24 lines]
> Transducer able to produce cavitation must probably be a sandwich type -
> if this was not a special construction, that is not typical.

The transducer was a neat little item that came with some of the
weird kits sold by Information Unlimited. I haven't seen any others
like it or if anybody else ever used a ring of piezo-ceramic mounted
on the inside face of a transducer. That it could be driven by a
simple LM555 oscillator circuit and produce enough ultrasonic energy
for cavitation really amazed me.

I see the project is still available these days along with the
transducer, but I would like to build one just to tinker with the
design and see if it could be improved upon.

Ron

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Natural Science Forum / Physics / Acoustics / June 2004

The Radiation Pattern