Fact or Fiction?
Decker
some thieves destroyed all the glass cases in a jewelry store using an
ultrasonic sine wave signal generator. I know that the right frequency
can break a wine glass and I've seen focused ultrasound set fire to
paint on a wall, but I was wondering if flat pieces of glass could
really de destroyed just by using ultrasonic waves? They gave a little
"demonstration" where the frequency of the signal generator kept going
up and up and up until a piece of plate glass shattered. Fact, or
Hollywood silliness? Thanks.
G. Decker
Savant
I saw that episode and actually irritated my wife to some extent by
continually muttering "BS"... :-)
Here's my take on the collection of inaccuracies in that particular
episode:
- For starters, the signal generator necessary to generate the tone is
not uncommon. The writers made it sound like this was some sort of
marginally contraband software, available only on the Internet "black
market." This is misleading. Many freeware and shareware signal
generators could produce the necessary signal. Further, many
commercial WAV editors (available from Sony and Adobe, among others)
have built-in generators that could produce the signal.
- Second was the use of an "MP3 player" to reproduce the signal. The
signal in question would have to be ultrasonic - higher than humans
could hear. (Hence the inclusion of a dog in the sub-plot.) My
understanding of MP3 compression would lead me to believe that
reproduction of such an ultrasonic wave would be impossible.
- Third, I believe the boombox-like device used to reproduce the signal
would be highly directional for the ultrasonic frequency in question.
Even at a high amplitude, playing back the signal over such a device
would create a "beam" of sound, making it quite difficult to shatter
*all* the glass in the jewelry store.
- Finally, the aforementioned boombox-like device was "smuggled" into
the jewelry store in a large, paper shopping bag. I believe the paper
of the bag in question would be of sufficient thickness to
significantly attenuate the ultrasonic wave. Thus making the whole
thing even more implausible.
If I may bloviate furthre, I find that the TV shows that fall under the
"forensic fiction" genre tend to treat sound with an elevated level of
fantasy. I have seen repeated use of "noise reduction" for high-noise
audio tracks where the technician pushes a button and the background
noise is magically removed, revealing the clear-as-day voice of a
killer, suspect, or witness. This mistreatment of the what the
techology can actually do gives less credence to the other technologies
employed, IMO. E.g., digital photos that are magically "enhanced" to
reveal the fine print on a distant prescription bottle; fingerprints
scanned into a database, providing a "match" in under a second (even
the fastest computers could not compare millions of fingerprints to one
sample that quickly); and other fantastical technology that, even if we
go a couple more decades in the future, are unlikely to ever
materialize.
It is my hope that, in general, these sorts of shows are taken for what
they are - fictional and ofttimes fantastical representations (in
truth, they are examples - even archetypes - of near-future sci-fi) of
what true forensic scientists (who rarely, if ever, are involved in
shoot-outs or interrogate suspects, btw) contribute to our justice
system.
OK - off my soapbox now! :-) :-)
Best regards,
Savant
Decker
this premise in a lot of different things from Japanese Anime to
MacGuyver, where an ultrasonic beem shatters glass. All figments of the
imagination or can high intensity ultrasound do that? I know sonic
booms can shatter glass through what is essentially shock excitation I
suppose.
G. D.
Savant
> I agree with you about all the details being wrong, but I have seen
> this premise in a lot of different things from Japanese Anime to
> MacGuyver, where an ultrasonic beem shatters glass. All figments of the
> imagination or can high intensity ultrasound do that? I know sonic
> booms can shatter glass through what is essentially shock excitation I
> suppose.
Yes, yes. Find the right resonant frequency - often not even an
ultrasonic one - and you can get anything to resonate to the point of
amplification, resulting in resonance that continually reinforces
itself, ultimately building to the point of destruction. Nikola Tesla,
in his day, was rumored to have built a handheld resonator that would
generate low enough frequencies to resonate building structures. The
way the story goes, he would go for a stroll around Manhattan, find a
construction site, affix his resonator to the steel framework of a
building underconstruction, and give the workers the fright of their
life! Before anyone could figure out what was going on (and,
presumably, before anyone could get hurt), he would detach his device
and flee the scene... :-)
Anyway, I digress. The answer is, yes, the phenomenon itself is very
real.
Ron Capik
> Decker wrote:
> > I agree with you about all the details being wrong, but I have seen
> > this premise in a lot of different things from Japanese Anime to
> > MacGuyver, where an ultrasonic beem shatters glass. All figments of the
> > imagination or can high intensity ultrasound do that? I know sonic
> > booms can shatter glass through what is essentially shock excitation I
> > suppose.
>
> Yes, yes. Find the right resonant frequency - often not even an
> ultrasonic one - and you can get anything to resonate to the point of
> amplification, resulting in resonance that continually reinforces
> itself, ultimately building to the point of destruction.
< ...snip.. >
I have experienced the catastrophic fracture of a three foot
long, quater inch diameter quartz rod, while cleaning it.
The thing broke in to inch sized segments from something
like a violin bow effect from sliding a methanol
soaked chem-wipe along the rod. The frequency I heard
just before the crash was well below the ultrasonic range.
Yes, glass can (and will ! ) shatter if you hit the resonant
frequency and the Q of that structure is high enough.
IMHO the show's premise was pure fantasy and a scientific
embarrassment!
Later...
Ron Capik
--
Decker
no more than a somewhat sophisticted solenoid in principle, and not
nearly as impressive as Gavreau's infrasonic whistle that could shake a
house down from five miles away when two of them were focused on a
structure.
G. D.
Decker
I've been sitting around practicing on the guitar and whenever I hit
the A note, the electric fan sitting right next to the amplifier would
just buzz like crazy. Mechanical structures have low resonance
frequencies; this is why soldiers have to break step before marching
over bridges. But I've heard of other musicians who have played various
notes and watched their lamps and other fragile things explode. I think
sonics is cool.
G. D.
Chris Whealy
> Anyway, I digress. The answer is, yes, the phenomenon itself is very real.
>
I've had first hand experience of this a few years ago. The choir at
our church hit the last note of a particular song, which wasn't
particularly high or loud, but it was exactly the right frequency to
cause a glass tumbler next to the platform to shatter. Very impressive!
But going back to show's like CSI et al - the science is not so much
bogus as grossly exaggerated. The points others have raised about
pressing the "remove background noise" button to clean up a noisy
recording or Horatio saying "enhance the image, will you" are all
completely correct.
However, my wife (who doesn't care much for the science) really enjoys
shows like CSI because they tell a good story - and to be fair, that is
their objective.
The science is (to a large extent) based on reality, but has been
greatly exaggerated in its capability, and the time-scale for getting
results has been greatly compressed. Taking the producer's point of
view, these are necessary adjustments in order to tell a good story.
I've worked with real forensic scientists, and believe me, they are not
glamorous fashion models! It would be more accurate to describe them
(or at least the ones I worked with) as the generation fashion forgot!
However, they are highly intelligent, methodical people who really
understand their subject and have a genuine desire to catch the
criminals. They do not however, drive around in Hummers making pithy
one-liners to criminals.
I would say that a more serious error with CSI is the fact that it looks
like the CSI's are the single crime-busting team - gathering evidence,
performing forensic analysis, then working out who committed the crime,
interviewing the suspects and finally arresting them. This just doesn't
happen. The CSI's gather the evidence and analyse it, then they hand it
over to detectives to perform the criminal investigation. The CSI's
take no part in the actual detective work.
I think this is a greater distortion of reality than the spurious science.
Chris W
--
The voice of ignorance speaks loud and long,
But the words of the wise are quiet and few.
---
Malcolm Hayes
"Decker" <ry...@quik.com> wrote in message
news:1161305027....@m7g2000cwm.googlegroups.com...
>I once had a book that showed how Tesla's thumper was constructed. It's
> no more than a somewhat sophisticted solenoid in principle, and not
> nearly as impressive as Gavreau's infrasonic whistle that could shake a
> house down from five miles away when two of them were focused on a
> structure.
>
> G. D.
>
And how does one "focus" an infrasound source!!!!
Gavreau has been much misquoted.
Cheers
MalcolmX
Angelo Campanella
> A week or two I was watching a TV program, CSI New York I Think, where
> some thieves destroyed all the glass cases in a jewelry store using an
> ultrasonic sine wave signal generator.
My reaction was a Guffaw.
Its as believable as Superman.
> I know that the right frequency
> can break a wine glass and I've seen focused ultrasound set fire to
> paint on a wall
If you were in the same room, you would have lost part of your hearing
(PTS), as the sound level required is somewhere between 140 and 170 dB,
and even then you have to be lucky. At Penn State, we burned cotton with
a 1KW (acoustic power, that is) siren. A classmate lost a bit of his
hearing on one demo day when he did not close the door of the siren
enclosure before turning on the siren motor and air blast. We never did
break any glass as students.
> but I was wondering if flat pieces of glass could
> really de destroyed just by using ultrasonic waves? They gave a little
> "demonstration" where the frequency of the signal generator kept going
> up and up and up until a piece of plate glass shattered.
Usually, the demo glass breaking uses a glass style known to be
breakable at a frequency and power of the sound generator. (One makes
such glass by cooling it in a manner that builds up extra interior
stress, rendering it sensitive to diturbance.) The siren was the weapon
of choice since it was possible to get good modulation of an air blast.
Sound level at the focus was about 160+ dB. The frequency was varied by
setting the siren motor rheostat to get the needed RPM.
> Hollywood silliness?
Netwrok desperation to get ratings. Any lie will do.
Angelo Campanella
Ethan Winer
> digital photos that are magically "enhanced" <
ROF,L. Yes, TV shows often do that with distant license plates too. It's
amazing how sharp and clear they can make it. The silliness should be
obvious to anyone who's zoomed way in on a JPG photo. :->)
--Ethan
Decker
>From what I understand, Gavreau's sound source was a six foot long
whistle powered by compressed air. While you *can* focus infrasound if
you have a large enough-- read that as *huge* reflector (maybe made out
of concrete)-- somebody discovered that two of Gavreau's whistles could
be pointed at a building and so the sound was "focused" in that sense:
the point where the two sound beams met.
G. D.
Greg Locock
news:1161372961.1...@h48g2000cwc.googlegroups.com:
I suggest you find out more about his demonstrations. Many of them were
at high frequency - a six foot tube would be of limited use with
infrasound. He did not destroy any buildings using infrasound - he made
a wall shake.
Cheers
Greg Locock
Decker
I'm not *that* interested in Gavreau. What I had read somewhere in
passing that his infrasonic whistles were based upon French police
whistles; the kind with a pea in it. But his research was done back in
the 60s and all I know about it is the few things that I read here and
there. I don't know if his technician was really killed by infrasound
or not, but it makes a good story.
G. D.
Decker
Angelo Campanella wrote:
> Decker wrote:
> > A week or two I was watching a TV program, CSI New York I Think, where
> > some thieves destroyed all the glass cases in a jewelry store using an
> > ultrasonic sine wave signal generator.
>
> My reaction was a Guffaw.
> Its as believable as Superman.
>
> > I know that the right frequency
> > can break a wine glass and I've seen focused ultrasound set fire to
> > paint on a wall
>
> If you were in the same room, you would have lost part of your hearing
> (PTS), as the sound level required is somewhere between 140 and 170 dB,
> and even then you have to be lucky. At Penn State, we burned cotton with
> a 1KW (acoustic power, that is) siren. A classmate lost a bit of his
> hearing on one demo day when he did not close the door of the siren
> enclosure before turning on the siren motor and air blast.
There used to be an old sci-fi show in the '50s or early '60s that
opened with the host doing some outrageous science demonstration--
usually with things that we would consider bloody dangerous these days.
But on this one show, this guy turned on an electronic signal generator
that had some kind of transducer (piezo or otherwise, I don't know) at
the focal point of a large parabolic dish. When he turned on the power,
the paint on the opposite wll burst into flames.
That demo was a hell of a lot more interesting than the sci-fi story
that followed, lol. But I assume because the dish was parabolic, that
the sound wasn't free to radiate a whole lot but was focused like light
with a lens. Can an electronic ultrasound source even produce 170 dB of
ultrasound?
> We never did
> break any glass as students.
Out of curiosity I tried to find out if I could get my electric guitar
tuner to tell me the resonant frequency of a wine glass. When I pinged
it with a finger, the tuner read 437 Hz. I read somewhere-- don't know
if it's true-- but to break a glass the sound has to be within 1/2 Hz
each way. I had planned on trying to break the glass just using sound,
but I had never gotten around to it. :-)
I've come across different websites where one says the glass has to be
thin, another says the glass must have bad resonance, while another
says it must have sharp resonance, and one website says it must have a
particular composition or the experiment won't work. But I had seen a
glass broken on an old kid's show many many years before, and the glass
was just ordinary glass placed in front of a speaker. The sound wasn't
very intense, although some sources says the sound has to be over 100
dBs or more. Maybe sometime soon I'll find out for sure just what it
takes just for the heck of it.
G.D.