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"Cone of Silence" Possible Say Scientists

Posted by ScuttleMonkey on from the is-leonard-bernstein-licensed-to-kill dept.

Ponca City, We Love You writes "The 'Cone of Silence,' once a staple of 1960's television shows, is now possible say scientists at Duke University who first demonstrated a working 'cloak of invisibility' that works at microwave frequencies in 2006. Such a cloak designed for audio frequencies might hide submarines in the ocean from detection by sonar or improve the acoustics of a concert hall by effectively flattening a structural beam. Although the theory used to design such acoustic devices so far isn't as general as the one used to devise the microwave cloak, the finding nonetheless paves the way for other acoustic devices. 'We've now shown that both 2-D and 3-D acoustic cloaks theoretically do exist,' says Researcher Steven Cummer. 'It opens up the door to make the physical shape of an object different from its acoustic shape.'"

17 of 90 comments (clear)

  1. Light on details... by ecavalli · · Score: 2, Interesting

    Sadly the article is sorta light on details.

    Anyone have some insight on how exactly this sort of thing is accomplished, aside from the article's reliance on materials that seemingly don't exist yet?

    1. Re:Light on details... by thelamecamel · · Score: 5, Informative

      It seems they're importing ideas from photonics and metamaterials - light and sound, they're all waves. What's been done with light (in Britain and Germany IIRC) is some object has been surrounded by a 'cloaking device', and for one specific wavelength of light, the cloaking device and object become completely transparent and invisible. Light flows through the cloaking device and around the object that's being hidden (well that's the hand-wavy explanation). To do funky stuff like cloaking, you need (in optics) a material with negative refractive index (so light seems to travel backwards). People get this by arranging tiny (smaller than the wavelength of light involved) resonators in a regular pattern. The light wave "doesn't see" the individual resonators, but instead "sees" an overall medium. However, this medium can have quite abnormal properties (such as negative refractive index). Another way of looking at the device is that you surround the object with resonators that specifically cancel out any effect on the sound/light wave that the object makes. So you get no net effect on the wave, so it's as if the object wasn't there. Presumably the people at Duke have transplanted some designs for light and have worked through the corresponding acoustic wave equations to find "negative refractive index sound" (though i'm not sure what their resonators would look like, because light is more complicated than sound and most light metamaterial designs use properties of both E and H components of light. Maybe they can cheat because sound travels faster in, say, wood than air)

    2. Re:Light on details... by tomhath · · Score: 2, Funny

      The details on how they do it are in the audio portion of the article. What? You didn't hear the audio? What?

  2. Max vs. the Chief by pipingguy · · Score: 4, Funny

    Max: What?
    Chief: What?
    Max: What?
    Chief: What?

    I've always wanted to build one of those, I even have a sketch, bill of materials, etc.

  3. The invisible cone by Anonymous Coward · · Score: 4, Funny

    Here is an image to explain it all:
    http://icanhascheezburger.com/2008/01/12/funny-pictures-invisible-ice-cream-cone/

    1. Re:The invisible cone by myth_of_sisyphus · · Score: 3, Funny

      That reminds me of trying to explain "I can has cheezburger" to my hairstylist.

      While cutting my hair one day, she mentioned she loved taking pictures of her cats.

      I said "You should check out this new craze. It's called "I can has cheezburger" and you take a picture of a cat doing something, and then you put a caption on it that is clever, then you post it on the internet."

      She says "I already go to a site and upload my cat pictures."

      I say "Well, it's not really cat pictures. It kind of 'transcends' cat pictures and becomes something else. Kind of a "meta-cat picture".

      She says "....uhhhh...what?..."

      I say "I can't really explain it, you kind of have to see it. Go to this website: 'I...can...has...cheezburger... spelled with a z and no 'e'"

      She says "....uhhhh...what?...."

      I say "I'll write it down...the site is named after the first cat picture called "I can has cheezburger". Now that cheezburger cat is famous in his own right. He's called 'Happycat'."

      She says "the pictures are of cats eating cheeseburgers?"

      I say "No, just captioned cheezburger."

      She says "Ok"

      She now thinks I'm completely insane and is silent for the rest of the haircut.

  4. When is acoustic shape same as physical anyway? by noidentity · · Score: 4, Insightful

    'It opens up the door to make the physical shape of an object different from its acoustic shape.'

    Since when has an object's acoustic shape ever matched its physical shape to begin with? It's usually more like a sphere.

    1. Re:When is acoustic shape same as physical anyway? by neapolitan · · Score: 4, Funny

      I had a girlfriend once whose physical shape was AWESOME, but her acoustic shape was terrible. Believe me, you don't ever want to be in that situation. Now, the ones that are nearly spherical are easily identified from a distance, and I tend to stay away from them.

      --
      Slashdotter, ID #101. UIDs are in binary, right?
  5. "Cone of Nonsense" Possible Says Teckla by Teckla · · Score: 4, Funny

    Researchers at the Teckla Institute for Scientific Advancement have determined that it's possible to have a "Cone of Nonsense" that remains stable for months, even years.

    "Take, for example, the Cone of Nonsense generated at Slashdot, an online site dedicated to News for Nerds," says Dr. Teckla, a long-time scientist at the Institute. "We've identified at least two powerful Cone of Nonsense forces there, which we've named the 'Roland Piquepaille Effect' and the 'Ponca City, We Love You Force'."

    Combine these potent forces with 'ScuttleMonkey Energy', and the result is a stable, if frightening, Cone of Nonsense.

    "We're not sure what happens if you enter this Cone of Nonsense," commented Dr. Teckla, "But we're pretty sure it drops your I.Q. by 50 points.

  6. bad news for bats by Anonymous Coward · · Score: 5, Funny

    "It opens up the door to make the physical shape of an object different from its acoustic shape."

  7. A staple of 60s television shows? by Chess_the_cat · · Score: 2, Interesting

    The only show I can think of that featured the Cone of Silence was Get Smart! What other shows featured this technology?

    --
    Support the First Amendment. Read at -1
  8. Already using one by Whiteox · · Score: 5, Funny

    Every time my wife asks me to do something, I don't hear it.
    Every time I ask her to do something, she doesn't hear me.

    --
    Don't be apathetic. Procrastinate!
  9. Can't find better references by MonkeyBoyo · · Score: 4, Informative

    Here is the old theoretical paperOne path to acoustic cloaking, New Journal of Physics, v. 9, 45, 2007. [pdf reprint] The Science Daily article is just a reprint of the Duke press release. Steven A. Cummer seems to provide PDF "reprints" of all his papers but the new one isn't in that list. Nor can it be found on David Smith' page, David Schurig's old Duke page, or his new NC State page, Sir John Pendry's page, or Anthony Starr's page.

  10. Motels by Porchroof · · Score: 2, Interesting

    Every motel room should have one.

    --
    Fata viam invenient.
  11. Hide submarines? by barzok · · Score: 2, Insightful

    Just change how you look for them. Instead of looking for signature noise, look for a "hole" in the background noise of the ocean.

    1. Re:Hide submarines? by thelamecamel · · Score: 4, Informative

      Nup. The really cool thing about this device (for the light cloaking devices that have been built, anyway) is that you don't block the noise behind the submarine. However as I commented below, I don't think these devices would hide the noise of the submarine or whatever was within the cloak, they would just allow sound to pass through the cloaked submarine as if the submarine was not there. The other problem is that these cloaks only work for a limited frequency range.

  12. Not a cone of silence! by thelamecamel · · Score: 5, Informative

    The devices the article talks about are not what you want from a cone of silence. What the researchers are proposing is something that will hide an object from external noises - as in the object will not affect any sound waves heading towards it, they will just pass straight through as if the object and cloaking device were not there. The proposed device WILL NOT contain noise created by whatever you're trying to hide, so the bad guys can still listen for a submarine's engines, they just won't be able to use active sonar to find the submarine.

    If you want a cone of silence, then you put yourself in a noise isolation chamber. Or if you want something cooler, then you put yourself in the acoustic equivalent of a gap-defect photonic crystal, which is a series of cylindrical rods arranged in a hexagonal lattice with one removed. A particular wavelength of sound will be reflected by this lattice, so if you're in the middle of that gap and you sing at that frequency, no-one outside the lattice will be able to hear you. Of course, you will very quickly become deaf because the sound is all reflected within the defect rather than absorbed, so the noise from your singing builds up.