[LAU] New 'acoustic metamaterial' cancels sound

[Peter]

Dear

Am 08.03.19 um 23:17 schrieb David W. Jones:

> Thanks, I was visualizing it as a sheet of material you could just hang like a curtain. I think the damping frequency can be changed for different versions of the material?


Yes you could, and you could could put several on a tube. However, this
device is explicitly build to be open in the sense that air can flow through
it. For a curtain like device you can build standard meta-materials,
see e.g. wikipedia for an explanation. While meta-materials are typically
build for electro-magnetic waves, the principle does work for sound waves.

The main problem is, you need sub wave-length structures where the total size is
than a few  wave lengths, which makes it unfeasible for low frequencies in a studio,
as the curtain needs a 'considerable' thickness.
Nevertheless you could build band gap material blocking sound in a frequency range,
much larger than that of the ring, which is a special purpose device.

A more typical feature would be blocking the EM wave with the frequency of a few
GHz, block the Wifi and the let the light through. And the most funny application
is the invisibility-cloak with which you can hide things so small you wouldn't be
able to see without the invisibility cloak. But but works, just too expensive to build
on a macroscopic scale.

Best regards,
Peter