Ultrasonic

[Rich Grise]

On Thu, 07 Apr 2005 13:16:57 -0700, Larry Brasfield wrote:

"Guy Macon" <http://www.guymacon.com/> wrote in message
news:115b2ospm074p82@corp.supernews.com...
Korben Dallas wrote:

I am requesting help to construct an ultrasonic device that emits sound
at about 25Khz. Unlike most ultrasonic devices, I want the device to
carry sound over 100 feet (or 30 meters) and still be over 140 decibels
at 100 feet (or 30 meters).

I will assume you mean dBA SPL, not dB. The Decibel is a ratio, not an
absolute quantity. What you wrote above translates to "I want the
device to ... be 30,000 times louder than at 100 feet." 30,000 times
louder than what?

As Mr. Pefhany has helped me realize in sci.electronics.basics, the
Decibel is also used for sound pressure levels, with the 0 dB reference
point being 20 uPa. The dBA (and dBC) reference levels follow a function
determined by perception among humans, and are not defined above the audio
range. So the OP may well have meant "dB". (I agree that bare "dB"
should be cast out of our lexicon for absolute measurents, but it's not up
to us.)

Is that the same as "the loudness the sound of a baby mouse urinating on a
desk blotter at 1 meter"?

Thanks,
Rich

 

[Larry Brasfield]

"Rich Grise" <richgrise@example.net> wrote in message
newsan.2005.04.09.16.32.54.525044@example.net...

On Thu, 07 Apr 2005 13:16:57 -0700, Larry Brasfield wrote:
....
As Mr. Pefhany has helped me realize in sci.electronics.basics, the
Decibel is also used for sound pressure levels, with the 0 dB reference
point being 20 uPa. The dBA (and dBC) reference levels follow a function
determined by perception among humans, and are not defined above the audio
range. So the OP may well have meant "dB". (I agree that bare "dB"
should be cast out of our lexicon for absolute measurents, but it's not up
to us.)

Is that the same as "the loudness the sound of a baby mouse urinating on a
desk blotter at 1 meter"?

Close. Maybe it was 1 cm, but that reference is supposed
to be just at the threshold of audibility (for some people at
some frequency; I know not the details.)

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

 

[John Woodgate]

I read in sci.electronics.design that Rich Grise <richgrise@example.net>
wrote (in <pan.2005.04.09.16.24.48.144369@example.net&gt about
'Ultrasonic', on Sat, 9 Apr 2005:

On Thu, 07 Apr 2005 19:45:27 +0000, Guy Macon wrote:
Mark Jones wrote:

140dB at 100 feet????

This comes close: 138dB at 100 feet:
http://www.victorysiren.com/x/

This shows the power of a good design. What I calculated to require 10
billion watts using speakers and amplifiers only took 100,000 watts
(180hp) using compressed air and a rotor.

does anyone know why they are specing 10dB loss per distance doubling
rather than 6dB?

Probably ground clutter.

It's probably an allowance for atmospheric absorption, but that varies

hugely with frequency and humidity.
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
'What is a Moebius strip?'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Scott Miller]

I wonder what they guy's trying to do? Shoot down flying saucers?

Or save the Earth from pure evil, perhaps. It should be noted that Korben
Dallas is not classified as human. He's a meat popsicle.

http://www.imdb.com/title/tt0119116/

I think he's just out to duplicate ATC's 'HyperSonic Sound' system. I don't
think he's going to get far... I'm pretty sure they designed some sort of
novel emitter from scratch. US patent 6,044,160 looks like it might be the
one. Not sure how well it actually works, but they're getting a lot of
press.

If you go to the USPTO's site and search on "Norris, Elwood" you get a lot
of hits related to this.

Scott

 

[Rich The Newsgropup Wacko]

On Mon, 11 Apr 2005 16:05:48 -0700, Scott Miller wrote:

I wonder what they guy's trying to do? Shoot down flying saucers?

Or save the Earth from pure evil, perhaps. It should be noted that Korben
Dallas is not classified as human. He's a meat popsicle.

http://www.imdb.com/title/tt0119116/

Oh, yeah, dood, that Milla Jovovitch is HOT! I love little tits! And
chicks that are smarter than Bruce Willis. ;-) (which, admittedly, doesn't
narrow the field all that dramatically, AFAICT.)

Interestingly, at the resolution/denouememt, the Fifth Element turns out
to be Love.

I think he's just out to duplicate ATC's 'HyperSonic Sound' system. I
don't think he's going to get far... I'm pretty sure they designed some
sort of novel emitter from scratch. US patent 6,044,160 looks like it
might be the one. Not sure how well it actually works, but they're
getting a lot of press.

If you go to the USPTO's site and search on "Norris, Elwood" you get a lot
of hits related to this.

Thanks!
Rich
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[another awful ons snipped - maybe I should change that file!]