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Acoustic "Superlens" Could Make Subs Invisible
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."
Title should be "Acoustic superlens could make subs inaudible".
Thanks to this ground-breaking scientific research, submarines will be even better equipped to collide with each other.
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......
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?
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.
Passive sonar, on the other hand, still works fine.
After all, the thing's got to have a tailpipe.
How can I believe you when you tell me what I don't want to hear?
Oh noes! Teh whales! You're right - the entire western Navy should just pack up and go home. I'm sure our enemies, being the reasonable and thoughtful people they seem to be, will follow suit.
Another day, anther Slashdot cloaking device story.
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?
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.
You don't know what an SEP 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....
"City hall" in German is "Rathaus" Kinda explains a few things......
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.
They will still have to de-cloak to fire their torpedoes ...
Wrong again. We equip the whales with the lens-thingy, sonar gets bent around them, they won't get hurt, the environmentalists are happy. Then we equip them with lasers. Stealthed killer whales with friggin' lasers, dude. World domination, here I come. Muhahhahahahhaaaaa.....
Ubi solitudinem faciunt, pacem appellant.
"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.
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.
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?
Nothing to see here but us trolls...move along...
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 makes it to the seabed (exceptions apply, for certain water depths, etc, but still, so much sound is lost all the time that you couldn't use this... you'd get false alarms continually). In the second case, there are no real independent sources of sound that could be blocked by a passing submarine that you could use to detect them (or we'd be doing this already). So realistically, this is probably not a viable means of detecting a submarine.
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 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).
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