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The Military Science

Acoustic "Superlens" Could Make Subs Invisible 136

Posted by kdawson
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."
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Acoustic "Superlens" Could Make Subs Invisible

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  • by Anonymous Coward on Friday May 29, 2009 @09:13AM (#28137633)
    Title should be "Acoustic superlens could make subs inaudible".
    • Re: (Score:1, Funny)

      by Anonymous Coward
      Ray Charles disagrees.
    • by Arthur B. (806360) on Friday May 29, 2009 @09:15AM (#28137657)

      No. They may still be audible, but ultrasound will appear to go through them as if they were water.

      • Re: (Score:1, Funny)

        by Anonymous Coward
        You must be fun at parties.
      • by Anonymous Coward on Friday May 29, 2009 @09:42AM (#28137979)
        Yeah I can see it now.........
        Capt. Bart Mancuso: All back full.
        Lt. Cmdr. Thompson: Captain...
        Capt. Bart Mancuso: I said, all back full!
        Lt. Cmdr. Thompson: Back full, aye.
        [the Dallas reverses, churning the water]
        Seaman Jones: Captain, we're cavitating, he can hear us!
        Capt. Bart Mancuso: No he can't we have that new super lense thingy that makes us inaudible!
        Lt. Cmdr. Thompson: No Captain, you don't understand it doesn't make us inaudible to people only to sonar!!
        Capt. Bar Mancuso: Oh Crap!
        • Re: (Score:3, Informative)

          by sunking2 (521698)
          I always hated the extra dialogue that they had to throw in for lack of a narrative. Like Mancuso had to have what was happening explained to him. And that whole first scene with Jones and the new sonar guy was grueling. As if going through sub school and being trained he would have no grasp of simple concepts of his job.
          • by smithmc (451373) *

            Jones: So, like Beethoven on the computer, you have labored to produce... [rrrrrip] A biologic.

            Beaumont: Duh whuuutt?

            Jones: A whale, Seaman Beaumont, a whale.

            C'mon, it was funny, admit it.

      • by LWATCDR (28044) on Friday May 29, 2009 @11:17AM (#28139207) Homepage Journal

        Which will not matter at all.
        Search sonar uses low to medium frequencies not ultrasonic ones.
        Also a large amount of the searching involves using passive sonar. Going active is kind of like using a spot light. Yea you can see but everybody can see you from an even greater distance.

      • by sean.peters (568334) on Friday May 29, 2009 @11:27AM (#28139323) Homepage

        "Ultrasound" (generally understood as meaning sound of a frequency too high to hear... i.e. more than 20khz) is pretty well useless in submarine detection, as high frequency sound has a very, very short propagation range in water. If they get to the point where they can do this with some frequency range that can go more than a few meters without being attenuated, then color me interested. But I'm guessing that would require an apparatus so huge that you wouldn't be able to deploy it anyway - the resonant cavities have to have a size of the same order of magnitude (maybe 1/4 wavelength?) of the sound wavelength... and for frequencies with any hope of propagating far (you're typically talking from 60 Hz to a few Khz), the wavelengths are HUGE - around 25 meters for 60 Hz. Bear in mind that you apparently need an array of these cavities, so you're talking about a rather enormous system.

        • I know, replying to myself is bad form, but... various navies also use anechoic coatings [wikipedia.org] that are conceptually similar to this. The difference is that they are tuned to absorb incoming active sonar pulses of a frequency that you think your enemy is likely to use. They also have an effect of muffling any sounds radiating from your own boat.

        • by Alex Belits (437) * on Friday May 29, 2009 @11:47AM (#28139567) Homepage

          The trivial solution would be a cavity filled with water same shape and size as the submarine, at the same position as the submarine.

          • Re: (Score:3, Insightful)

            by Ninkazu (698399)

            The trivial solution would be a cavity filled with water same shape and size as the submarine, at the same position as the submarine.

            Why is this marked interesting? Clearly it's funny, since the above suggestion is to have the so-called submarine actually just be a pocket of water. i.e. no submarine.

            • The trivial solution would be a cavity filled with water same shape and size as the submarine, at the same position as the submarine.

              Why is this marked interesting? Clearly it's funny, since the above suggestion is to have the so-called submarine actually just be a pocket of water. i.e. no submarine.

              You could also fill the sub with water, though the crew might not like that...

        • While true that it's useless for submarine detection - torpedo ranging and homing sonars use higher frequencies. Making yourself less visible or invisible in these frequencies is a Big Win.

          • You don't need a metamaterial based apparatus like this to accomplish that - you just need an anechoic coating... which we already have.
            • Word is (AIUI) that anechoic coatings will work until another couple generations of Moore's Law work their magic and torpedo designers can pack better amplifiers and signal processors into the fish.

              • My thought is that the "cloaking" approach is going to be just as vulnerable to this - you know it won't be able to perfectly cloak a submarine, just give you some number of dB improvement in the ability to hide. And that will end up being vulnerable to improvements in amps/SPs as well.

                And I have my doubts about the premise, anyway... you don't just have to improve the amps and signal processors, you would also have to improve the transducers. I'm doubtful that the amps and SPs are really improving as fast

              • by Kagura (843695)

                Word is (AIUI) that anechoic coatings will work until another couple generations of Moore's Law work their magic and torpedo designers can pack better amplifiers and signal processors into the fish.

                We need more transistors in our anechoic tiles!

          • by LWATCDR (28044)

            They are higher but still well below the ultrasonic range. You would still have some pretty big resonate chambers to deal with. And anechoic coating will probably work better.

        • by Pigeon451 (958201)
          Actually water is a good propagator of sound, with a low attenuation compared to air or other materials. But over the length scales required for submarine detection, high frequencies would attenuated quickly compared to low frequencies (which is probably what you meant). It depends on what you define as "high frequency".
        • by instarx (615765)

          I smell baloney. First, where did you get the idea that ultrasound would be used? I read nothing of the sort. So your statement that ultrasound only travels a few meters in water may be true, but has no bearing on the topic and certainly doesn't prove that anyone was wrong or that the technique would not work.

          Second, you are apparently confused about the need for huge "resonant cavities". What resonant cavities? We are not talking about sizing antennae to detect EM radiation, but about simple propagation

      • by jonadab (583620)
        > They may still be audible, but ultrasound will appear to go through them as if they were water.

        Yeah, theoretically.

        Thing is, "invisible to sonar" is not the same thing as "undetectable and untrackable". Ships would just have to start using more than traditional sonar. Given how *long* sonar has been in use essentially unchanged, I'm not sure this is really a big deal. An upgrade to the sonar room was probably overdue anyway.

        Being invisible to traditional bounce-back-to-the-source sonar is one thing,
    • by pjt33 (739471)

      In addition, the summary currently describes it as "an aluminum array of narrow-necked resonant cavities filed with water". Maybe someone has managed to create a cunning way of using water to smooth off rough surfaces, but I think it's more likely that the summary is missing a letter.

    • by ae1294 (1547521)

      Article translation....

      1974 VW van muffler converted for military use for only 700 trillion dollars.
      (Military leaders say in between snorting lines of coke that "they really really needed this to stop the red menace uhhh I mean terrorists...")

      News at 11.... am...

  • Invisicrash (Score:5, Funny)

    by MadLad (1331393) on Friday May 29, 2009 @09:13AM (#28137643)
    Thanks to this ground-breaking scientific research, submarines will be even better equipped to collide with each other [wikipedia.org].
    • Not really.

      It just means that, as a sub commander, the only thing you can now be sure of is where something is, rather than where something isn't.

      So, in order to avoid crashing into invisible, cloaked submarines, all a sub commander will have to do is crash into the seabed.

    • Re: (Score:2, Funny)

      by metacell (523607)
      "Ground-breaking"? You crack me up ;-)
  • Ideas.... (Score:5, Interesting)

    by cbiltcliffe (186293) on Friday May 29, 2009 @09:17AM (#28137669) Homepage Journal

    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.

    • Re:Ideas.... (Score:4, Interesting)

      by Amouth (879122) on Friday May 29, 2009 @09:36AM (#28137899)

      i don't think this is nearly as focused as say a lens's ability to focus a nm of light.

      i would think it would work on a wide range of frequencies (some better than others) but all should be better than nothing.

      think of the sound proofing and dampening they use in recording studios.. sure it doesn't stop everything but it works well on a wide range.

      now that said.. this is almost like the radar absorbsion on stealth planes.. - if you have 2 towers shooting back and forth and the plane goes inbetween you can track it based on the lack of reflection.

      It might be possiable to do the same to a sub using this except it might be easier.. as sonar does pickup the reflections from the bottom and also veriations in water preasure (if the gain is high enough).. i would think that something like this would show up as a void in the response - and there for trackable.

      • It sounded to me like this "bends" the sound around the object, and the sonar would simply reflect off the ocean floor below the sub, not leave a blank spot on the sonar, but I could be wrong.
      • Re:Ideas.... (Score:4, Interesting)

        by cbiltcliffe (186293) on Friday May 29, 2009 @09:50AM (#28138115) Homepage Journal

        i would think it would work on a wide range of frequencies (some better than others) but all should be better than nothing.

        True, but "ultrasound waves" essentially covers any sound from 20kHz up. There's no way it can work on that kind of a range effectively enough to hide something as big as a sub from someone who really wants to find it.

        Comparing it to the soundproofing in recording studios doesn't really work, as audible sound only covers, at most, 20Hz to 20kHz. For most people, it's more like 35Hz to 18kHz. As well as that, studio sound baffling absorbs sound indiscriminately.

        I get the impression from this that it's not absorbing it so much as redirecting it around the cloaked object. TFA (which I've read now) compares it to similar cloaks which have been worked on for visible light. These light cloaks redirect light around the object, so you see what's behind it. A sonar cloak would have to do the same thing to be effective, otherwise the viewing vessel would see:

        seabedseabedseabed.........seabedseabed

        Any gap in the seabed would indicate a cloaked sub between you and the bottom.

        • by Amouth (879122)

          they refer to the cells as "array of narrow-necked resonant cavities"

          while i agree that it more than likely will not "hide the sub" i have no dobut that at some point it can help in the hiding of the object.

          if you can distort the reflection of the sonar you can alter the perception of your placement to the reciver. (unless they know how it has been distorted)

          i see this as just making it harder to identify and pinpoint a sub. Another comment i say makes alot of sence too.. Via time in transit - if it has t

          • Via time in transit - if it has to wrap the sound around there will be a ever so slight delay - meaning you will see the shape of the sub as a depression in the image from the sea floor reflection,

            I can see this, although the time difference is going to be minuscule. I could see something like that being noticed with a fairly smooth seabed, and with the detecting ship riding on smooth water. But once you throw a few waves into the mix, and a moderately craggy sea bottom, I'd think the signal:noise ratio would be impossible to work with.

            Of course, I could be wrong, as I have no idea how accurate sonar is. I'm just approaching this from a security guy's perspective, trying to figure out ways around

        • Not necessarily (Score:3, Informative)

          by sean.peters (568334)

          You need to consider two cases: active sonar (in which the searching ship is attempting to ensonify the target ship with sonar pulses, and then detect returning echoes) and passive sonar (in which the searching ship is just listening for sound emanations from the target). In the first case, you typically wouldn't be able to identify the submarine from a gap in return from the seabed - most of the energy in a sonar pulse ends up being entrapped in one or more "sound channels" in the water column, and never m

      • Actually it's the other way around - because this uses resonant cavities, it only works on a very small range of frequencies. But the 'super' thing about a superlens is that it can focus sound/light to a region smaller than any other kind of lens, 'beating the diffraction limit'.

        • by Amouth (879122)

          but if you read they haven't beaten the diffraction limit yet, for light yes for sound no - this is just as close as they have gotten

    • by still cynical (17020) on Friday May 29, 2009 @10:08AM (#28138363) Homepage

      You just have to modify the deflector array to rotate the shield harmonics. Problem solved, but you'll have to do it again every few episodes.

    • by Muad'Dave (255648)
      They already do [tritech.co.uk]. It's called chirp sonar, and provides enhanced resolution and target separation.
    • Yep, this particular design will work over a very narrow range of frequencies, because it uses resonant cavities, which are inherently narrowband. If they could build a design without the need for resonant effects, then in principle the acoustic cloak could work over a very large range of frequencies.

      The idea behind the acoustic cloak is essentially the same as the optical cloaks that have already been demonstrated: 'squash' space around the object to open up a hole in the universe, as seen by light/sound

    • Re:Ideas.... (Score:5, Informative)

      by rickb928 (945187) on Friday May 29, 2009 @10:32AM (#28138687) Homepage Journal

      The same techniques that are used in radar will be used in sonar;

      - Frequency agility will become the norm.

      - The cavities will be tuned at first mechanically. It wasn't so long ago that radar was tuned with physical cavities. I haven't kept up on very high powered sets, but I suspect they do it all electronically now. Magnetrons are pretty much declassé.

      - I would be surprised that pulse shaping and various AGC techniques are not already in use.

      - Backscatter sonar will be developed. This is just an exercise in computing power, and we got that nailed.

      - More useful than stealth or masking would be using superlenses for decoys. Nothing makes your sub commander's day like having 6 or 7 targets and KNOWING that only 1 or 2 are genuine. Torps are largely ineffective against decoys, and expose your position. In a robust countermeasures environment, whoever shoots first usually loses. They are dead from the bogey they didn't see, or prioritized wrong, shooting the decoy first. Whatever they shot at may or may not be real.

      I wonder if we have many lone attack subs out there. Teamwork solves a lot of problems. Using another sub's pings is the simplest of tactics. Backscattering off of your teammate is somewhat more interesting. Using an array to listen to your teammate's pings and map the hole is even more fun.

      Crap, I miss countermeasures. Wonder if the Air force is still hiring...

    • Harder to do than it sounds (pardon the pun).

      High power emitters (AFAIK/IIRC) pretty much work on only one frequency, which means (currently) that you have to carry two sets. Also, the transmitter arrays are pretty good sized, and there is only so much room available in a submarines nose or a ship's sonar dome. So while it's doable, there is going to be some pretty big impacts on design.

      But, as posted elsewhere, passive sonar still works and is actually the preferred method for tracking.

    • Already been done. There are radar systems that essentially use a burst of microwave noise. Bats and dolphins use multiple frequencies. It's unlikely this system in it's present state would fool a dolphin.

      Now, if you designed the system with electrically variable cavities, you'd be able to adjust it on the fly. The first few waves of a ping would bounce back, then you would disappear...
      • Now, if you designed the system with electrically variable cavities, you'd be able to adjust it on the fly. The first few waves of a ping would bounce back, then you would disappear...

        Unless the sound frequency was random for each chirp......
        That's along the lines of what I was thinking.

    • by tnk1 (899206)

      Well most submarines these days use passive sonar, which means listening for sound, rather than pinging things with active sonar. If you ping something, you'll easily get a target solution on it, but you'll also be painting a big fat target on yourself. If you are lucky, the contact didn't know you were there and you take them by surprise and take them out. If you are unlucky, they either suspected you were around or they are fast enough that they could send a torp of their own right at you as soon as yo

    • What if... (Score:3, Informative)

      by sean.peters (568334)

      then what happens if somebody comes up with a sonar that uses variable pitch?

      Someone's already come up with it - the AN/SQS-53. No link, as for obvious reasons the Navy is not keen on talking about the operating frequencies of its gear, but it's well known that it uses multiple frequencies around 3.5 KHz for active sonar, and it's got a passive sonar capability to detect between very low and rather high frequencies.

      • by 4D6963 (933028)

        No link, as for obvious reasons the Navy is not keen on talking about the operating frequencies of its gear

        From there [janes.com] : "Operating frequency is 3 kHz with a peak frequency of 192 kHz."

  • by grub (11606)

    When I saw "subs invisible" I thought "Cool, I can get rid of those 2 huge black boxes hooked up to the receiver" but no...
    • I'm assuming you're a guy......

      So paint them pink, and put OMG PONIES!!1!!1 stickers all over them, then put up an SEP.

      • by belthize (990217)

        Pink subs attract nurses and sink trucks.

        • Re: (Score:3, Informative)

          by cbiltcliffe (186293)

          You don't know what an SEP [wikipedia.org] is, do you?

          Read section 5.1.

          Nobody'll see pink OMG PONIES!!1!!!1 subs in a guy's apartment.
          Unless he's openly gay, or has a 5 year old daughter....

          • by belthize (990217)

            You've never seen this movie (http://en.wikipedia.org/wiki/Operation_Petticoat) have you.

            • Nope, I haven't.

              And I even Googled a bit to figure out what the heck you were talking about. But apparently not for the right stuff. Which isn't surprising, considering I haven't seen the movie....

              Guess I should have Googled all terms together. Then, your /. comment is first (Damn! Google is fast!) and the movie review on answers.com is second.

  • by Critical Facilities (850111) * on Friday May 29, 2009 @09:19AM (#28137691) Homepage

    Theorists have been working on materials that bend sound waves backward for several years.

    So you mean, if this technology moves forward, and ends up getting incorporated into conventional home/portable audio systems, we may be able to settle once and for all whether or not Paul is dead?

  • Redeeculous (Score:5, Interesting)

    by Ancient_Hacker (751168) on Friday May 29, 2009 @09:22AM (#28137739)

    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.

    • That's right... all forward progress needs to be stopped. All the creative people need to put on their headphones that squash intelligent thought. In fact, we should probably do it to everyone straight from the womb, just to make sure no free thinkers get by... You never know what might actually work until you try. It sounds like they have made some progress on something that even in one-dimension was thought to be impossible for a long time. Good for them!
      • by gardyloo (512791)

        It sounds like they have made some progress on something that even in one-dimension was thought to be impossible for a long time.

        Focusing in one dimension? You might want to rephrase that.

    • This just sounds like the perfect phrase to put in a grant proposal to get some Admiral to sign off on it.
      Admirals are not the ones signing off on this. It would be gates and congress or DARPA. In both cases, Gates controls them WRT DOD budget. And IMHO, with the exception of the ABL, I think that he is doing a damn good job.
  • by pushing-robot (1037830) on Friday May 29, 2009 @09:25AM (#28137779)

    Passive sonar, on the other hand, still works fine.

    After all, the thing's got to have a tailpipe.

    • Even so, reducing or eliminating the vessels visibility to active sonar is still a pretty big deal - active sonar is sometimes used for range confirmation prior to firing, and damn near all torpedoes use active sonar for ranging and homing.
       
      (Former submariner.)

      • Yes, but (Score:3, Informative)

        by sean.peters (568334)

        At frequencies actually usable for submarine detection, this apparatus would have to be freakin' enormous - the cavities would need to be on the order of the same size as the wavelength... so you're talking meters in diameter. And you apparently need an array of them. I don't think that's something you can drag around on your submarine.

        Not to get into a credentials war, but (former surface ship ASW evaluator) (have a masters degree in anti-submarine warfare from the Naval Postgrad School)

        • I hadn't thought about the freqs for submarine detection - but torpedo sonars use pretty short freqs, so it may be useful there.

    • Not so sure. Sound reflects at an abrupt change of medium/impedance. If these acoustic cloaks are like the optical cloaks, then the innermost part of the cloaking device has an impedance of zero, which reflects all sound. So it could get noisy inside the cloak if there's no damping...

    • its just waves. if they can create antiwaves in noise canceling headphones on the fly, surely they can create antiwaves in water near the "tailpipe", especially since the noise source is probably relatively unchanging and well characterized

      • by 4D6963 (933028)

        For one thing, noise canceling headphones have it easy because they're right before the ear, there's little difference in phase/delay between it it hears and what the ear hears. Besides, they only reduce things by something like 25 dB, and that's by taking into account the passive stuff, not just the cancelling.

        Further more it's complicated in something like a submarine because you're trying to cancel from the source, but there's not just one tiny source, the whole thing is making noise, and it's not like y

  • HoHum (Score:5, Funny)

    by senorpoco (1396603) on Friday May 29, 2009 @09:47AM (#28138061)
    Another day, anther Slashdot cloaking device story.
    • Another day, anther Slashdot cloaking device story.

      We'll know when they finally work by the absence of Slashdot stories on them (except for the delayed dupes).

  • by gr8_phk (621180) on Friday May 29, 2009 @09:49AM (#28138091)
    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?
    • I thought this was the Ravenous Bugblatter Beast of Traal [wikipedia.org] philosophy?
    • by stjobe (78285)

      Ostrich philosophy?! OSTRICH?!?

      Hand in your geek card immediately, son!

      It's the Ravenous Bugblatter Beast of Traal [wikipedia.org] philosophy!

    • Re: (Score:3, Interesting)

      by thelamecamel (561865)

      You could intentionally let a little bit of light/sound in and out at your favourite frequency. Or you could choose not to be entirely invisible, designing the cloaking device to warp your submarine into, say, the shape of a shark. All the sound that would have hit the shark will be spread across your submarine's surface (or if you design the cloak REALLY cleverly it could be focussed on your receiver). So with this kind of cloak, the enemy COULD see your submarine and receiver, but it would just be disg

      • the enemy COULD see your submarine and receiver, but it would just be disguised like a shark

        "Captain - we're picking up a contact on active sonar - doesn't look like a sub"

        "OK, what does it look like then?"

        "Uh, Captain, not sure, it's about the same size as a sub but it looks like.... looks like ... no that can't be right"

        "Come on sonar, spit it out"

        "Well sir, it looks like a giant shark"

        "Somebody go relieve sonar please".

        Might work....

        • Oops, I neglected to mention the 'shrink' part. It's a lot easier to shrink (and warp) a submarine than make it disappear entirely. Proper cloaks have a singularity on the inner surface of the cloak, as the entire inner surface has to seem like a single point. If you build the outer part of the cloaking device properly, but just give up when you get to a certain radius, then your cloaking device more or less makes the cloaked region appear much smaller than it really is, e.g. turning your submarine-sized

          • I like my idea better. Giant Sharks. Scarier that way. No submariner is going to be impressed with a regular sized shark. Even with lasers.
  • by Yvan256 (722131) on Friday May 29, 2009 @09:50AM (#28138103) Homepage Journal

    Researchers have previously developed materials that bend light in ways that appear to violate the laws of physics.

    If they have developed materials that bend light in ways that appear to violate the laws of physics, then it means the laws of physics need to be redefined. That's what science is. Formulas made from observations. New observations may modify your existing understanding of how things work.

    And if you can't accept that, you shouldn't call yourself a scientist.

    • Re: (Score:3, Insightful)

      by MozeeToby (1163751)

      The key word here is 'appear'. Meta-materials (which is what this is, just on a large scale) appear to violate the laws of physics but if you look more closely they don't. The point is that if you showed it to a college undergrad with decent physics knowledge they would say it violates the laws of physics, that doesn't mean the college kid is right.

  • Their acoustic meta-material uses resonant cavities. The problem with it is that resonance works perfectly for a specific frequency and not at all for different frequencies.

    A sonar cloak made of this material would be the equivalent of an invisibility cloak for people that are only capable of seing in a very narrow spectrum of Red: worthless if your enemy can "see" in more than one frequency.

    • by eh2o (471262)

      It is possible to make a broadband resonator using a fractal design. These are common in audio acoustics, the most basic design is the quadratic residue diffuser.

  • Kidney stones (Score:2, Interesting)

    by dvoecks (1000574)
    My first thought (aside from "invisible" submarines) is what this could do for kidney stones... Somebody with more knowledge on the subject may want to check my reasoning (the best part of /.), but I would think that better-focused ultrasound could really cut down on "collateral damage" from breaking up kidney stones, possibly allowing the technique to be used more effectively on a wider variety of cases.
    • There's already better techniques for breaking up kidney stones. One sends a small signal out and looks for a bounce from the stones. Once it sees the stones, and has measured their resonances, it sends a larger pulse along multiple paths to destroy the stone. I don't know if the new system is available out of the lab yet though.
  • They've already managed to vanish the subs from the original article it seems. Must be the refracted light and sound that completely goes around it. Or have they dived? I think I saw a periscope!

    Maybe they are just hiding from the sharks.

  • by JoelMartinez (916445) on Friday May 29, 2009 @10:26AM (#28138617) Homepage
    They will still have to de-cloak to fire their torpedoes ...
    • Sadly this is essentially true. Any time a sub fires a torpedo or a missle, it makes its location known to damn near half the world.
  • It's pretty rare that submarines are identified through active pinging, because, once you ping, everyone knows where you are. Instead you try and listen for other people, and that means machinery and cavitation. I could see using this technology to dampen expected sounds from internal machinery, but that would only work so long as the machinery actually makes predictable sound and one has to wonder if this technology would actually be better at damping than other technology. In any case, its certainly n

  • Sounds great! Now, can we make sure we don't have any spies in the Navy or the Military Industrial Complex who will sell the technology to the Israelis, the Iranians, the North Koreans, the Chinese, the Russians or anyone connected to Toshiba?
  • Not really needed (Score:5, Interesting)

    by whitroth (9367) <whitrothNO@SPAM5-cent.us> on Friday May 29, 2009 @12:03PM (#28139739) Homepage

    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

    • Re: (Score:3, Interesting)

      by smellsofbikes (890263)

      Using underwater thermoclines helps because pressure pulses (sonar) moving through thermoclines distort. Think refraction of light between air and water. It doesn't hide you, though: it just misrepresents your position. That's why subs since WWII have had bathythermographs [wikipedia.org], so they can map thermoclines to their advantage. If they know where the cold and hot areas are and people above them don't, they can use them.
      But it's only useful to keep you from getting hit by another sub's torpedo or a depth charg

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