invisible

basically the article says its possible to make an acoustic invisibility cloak that when worn would keep you from being detected on radar.

But another race is underway - to make an acoustic invisibility cloak. Sounds waves behave enough like light waves to be manipulated in similar ways, if you can make the 'metamaterials' that make cloaks possible. Metamaterials can bend - refract - waves in the opposite direction to natural materials, allowing physicists to play new tricks with them.

No one has yet made an acoustic metamaterial, but simulations points to possible ways of doing it. Chinese researchers last year suggested embedding rubber-coated gold spheres and water-filled pockets containing air bubbles in an epoxy resin. And this week a team in the UK showed that carefully sculpted silica and a few carbon nanotubes could make acoustic metamaterials for perfect sound proofing or even protection against earthquakes.

Today a group at Duke University in North Carolina, US, went one better. They have worked out that it should be possible to make a 3D acoustic invisibility cloak - something that had still been in doubt.

Such cloaks could make submarine's invisible to sonar, or improve acoustics by letting sound travel through, say, pillars at a concert hall. What the Duke team has to say about the materials that could achieve that is unknown for now, as the new results will appear in the journal Physical Review Letters on January 11.

While I'm sure there is plenty more theoretical work to be done, the next step is clear. Who is going to physically build an acoustic metamaterial first?