Inaudibility Cloaks

Rakish_Mottle

So the invisibility cloaks we were promised have remained stubbornly 'just over the horizon' ever since we first heard about them. Yes, we've seen unconvincing greenish images projected onto a rain mac mounted with hundreds of cameras, but the metamaterials with negative refractive indexes that can bend visible light completely around an object still haven't appeared.

Or maybe they have and we just can't see them.

Either way, you can apparently produce the same effect on sound-waves by precisely stacking special plastics drilled with particular arrays of holes.

Obviously the first thing that came to mind for the media was military applications, especially sonar cloaking, but the BBC article suggests that the same technology could be used for giving music venues better acoustics (presumably by 'removing' pillars etc. by allowing sound to pass through them unhindered) or even sound-proofing, though I don't really understand how the latter could work.

Seems to have been floating around a few months before anybody (except physicists?) started talking about it.

So - other potential uses? It makes me think of the architectural listening device Jessica discovers when the Atriedes first get to Dune but I'm sure that there's a lot of nicer potential applications.

grant

Hee!

"It's almost like someone could take a pencil and poke holes in a particular way in the plastic," he told BBC News.

Potential applications: Anything you don't want to be heard. From torture chambers to classified briefing rooms to engine blocks to hotel rooms. I've done some recording for video/movies, and it's *amazing* how many unwanted sounds there are even in a "quiet" environment. Crickets in the woods. The refrigerator in an empty house. Traffic near a campsite. Ooo - portable baffles you could put around fluorescent lights and air conditioners! Shh! No more hum!

Seth

This is going to be used against drummers, isn't it?

Joking, of course. Application in live sound, so there's less overspill from the kit and amps, could be useful where appearance is less of an issue.

EmberLeo

Rakish_Mottle said: the metamaterials with negative refractive indexes that can bend visible light completely around an object still haven't appeared.

Oh, I could swear they've managed some - I'm pretty sure I've read articles in actual Science magazines (probably Sci Am). It's just they haven't gotten to use them to cloak anything on a decently macro scale yet.

--Ember--

grant

I'm picturing the graphic now - an image with a row of diagonal lines on it, a little blurry, like a photo of liquid crystal....

I think the trick might be "visible light" - I'd have to look it up, but I believe it was demonstrating the principle by bending certain frequencies around something very small.

Duke did it with microwaves (possibly the one I'm thinking of, though it seems too old): http://today.duke.edu/2006/10/cloakdemo.html

And in Michigan, they did it with the infrared last summer: http://www.sciencedaily.com/releases/2010/07/100721164007.htm

So it's really just a matter of time.

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