projecting sound with a parabola and a cylinder

Combining the ideas of parabolic microphone/speaker and shotgun microphone, I wonder whether I could project high frequency sound (15 kHz for instance) fairly directionally with a small speaker/transducer at the focus of a parabola with 10 cm diameter, which in turn is attached to one end of a piece of 10 cm diameter pipe.

Normally the beam angle in radians is lambda/D (where lambda = wavelength, D = diameter of parabola), but would attaching it to the pipe help much? And how long does the pipe need to be?

I've found formulas/instructions on the web for building approx. parabolas by marking out a bunch of inversely tapering wedges on paper, cutting them out, and sticking them together. Would paper coated with transparent plastic film work for reflecting sound?

thanks, Bob

Reply to
Bob Fnord
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For high frequencies, smooth surfaces like that seems like a good "hobby" solution.

Reply to
Robert Baer

easy parabola recipe: put some plaster of paris in a bowl on a turntable. let it set whilst spinning.

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Reply to
Jasen Betts

I invented this, but someone else got credit because i did not publish in 1987. It uses ultrasonic projection from two dishes to focus audible sound near one point where the two ultrasonic beams meet.

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Reply to
alanfolmsbee

You are so full of shit, boy.

Reply to
WoolyBully

1987. It uses ultrasonic projection from two dishes to focus audible sound near one point where the two ultrasonic beams meet.

From what I see the cool picture of ultrasonic speakers is just a mockup. Here's the designers response to all the people that wanted to purchase. This was written about a year ago.

"Hi everyone,

Thank you for the kind words and interest in the project. The speakers you're seeing are actually just models I made, and they are purely for aesthetic purposes. These speakers are still in the concept stage, which means there is no working prototype of this design as of now. Hopefully that will change, so keep an eye out.

Thanks again, Adam"

BTW, I did see ultrasonic speakers used in a building at the University of Florida. There is a wall of tv's tuned to international channels, the speakers are mounted in a high ceiling and depending on were you stand you get audio from a particular tv. The listening diameter was about 3 feet. I'll check it out again this summer when I deliver my son to college* for his freshman year.

Mikek

*(send money) :-)
Reply to
amdx

Very cute! How big a containment building do you need? :-)

Reply to
Bill Martin

Yup. UofA is at the forefront of telescope technology. ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

I want everyone* to be very careful what you say, I think Jim is taking pride in UofA. Mikek

*especially you Larkin :-)
Reply to
amdx

That depends on how big a parabola you are casting.

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Art

Reply to
Artemus

You are beyond retarded*.

*even more so than Larkin is.
Reply to
WoolyBully

Could you give me more detail on the phrase "beyond retarded". Mikek

Reply to
amdx

Usually wrong.

Reply to
krw

1987. It uses ultrasonic projection from two dishes to focus audible sound near one point where the two ultrasonic beams meet.

..."peeked the imagination"?? eye gess hee kannut spel thut furst wurd sew wel.

Reply to
Robert Baer

Your IQ is 50 points higher than 'dimmie's'.

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You can't have a sense of humor, if you have no sense.
Reply to
Michael A. Terrell

That's not a very nice thing to tell Mike!

Reply to
krw

Thanks, I was hoping someone would say that! Bob

Reply to
Bob Fnord

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