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Acoustic "Superlens" Could Make Subs Invisible

Posted by kdawson on from the bending-it dept.

Al writes "Nicholas Fang and colleagues at the University of Illinois at Urbana-Champaign have created the first acoustic superlens, which could be used to create high-resolution ultrasound images, and perhaps ultimately make subs and ships invisible to sonar. Researchers have previously developed materials that bend light in ways that appear to violate the laws of physics, creating so-called optical superlenses. The acoustic superlens consists of an aluminum array of narrow-necked resonant cavities filed with water — the dimensions of the cavities are tuned to interact with ultrasound waves. When ultrasound waves move through the array, the cavities resonate and the sound is refocused."

4 of 136 comments (clear)

  1. Ideas.... by cbiltcliffe · · Score: 4, Interesting

    I haven't RTFA, big surprise, but just a thought...

    If the cavities have to be tuned to match the sound, then what happens if somebody comes up with a sonar that uses variable pitch?

    Or even just two separate sonar systems on a ship/sub/whatever, that use two different frequencies, with no matching harmonics.
    If something shows up on one, and not the other, then somebody's trying to hide.

    --
    "City hall" in German is "Rathaus" Kinda explains a few things......
  2. Redeeculous by Ancient_Hacker · · Score: 4, Interesting

    The claim of "invisibility" sounds like exactly what one would write in a grant proposal to the Naval Research Lab.

    Never mind it's very very unlikely.

    Any practical cloaking device is almost certainly going to work in only one linear direction and at one temperature and frequency.
      And imperfectly at best.
            And probably be larger than what it's trying to cloak.

    But sonar pulses are spread in frequency and can arrive from any direction, making such a cloaking device useless.

    This just sounds like the perfect phrase to put in a grant proposal to get some Admiral to sign off on it.

  3. Invisibility works both ways. by gr8_phk · · Score: 4, Interesting

    It's the ostrich philosophy - if you can't see it, it can't see you. If all incoming waves (light or sound) are diverted around the object, then it can't "see" anything. If it absorbs some, then it will appear dark against it's background. Granted, it doesn't take much light to feed a camera, but how do you make an exception for a little bit of it?

  4. Not really needed by whitroth · · Score: 4, Interesting

    I have it on good authority - I know someone who, in the early eighties, was in the "Hunt for Red October" command (COMOCEANSYSLANT) - who tells me that all a sub needs to do is drop below a cold current in the ocean, and they're invisible.

    What's more important is silence on the sub - she also told me about them finding a Soviet sub because of a noisy coffeepot (for real).

                          mark