Acoustic Cloaking Device & Metamaterials

The acoustic cloaking device works in all three dimensions, no matter which direction the sound is coming from or where the observer is located. By placing this cloak around an object, the sound waves behave like there is nothing more than a flat surface in their path. 


Turning to Nature: METAMATERIALS

To achieve this new trick, Cummer and his colleagues turned to the developing field of metamaterialsthe combination of natural materials in repeating patterns to achieve unnatural properties. In the case of the new acoustic cloak, the materials manipulating the behavior of sound waves are simply plastic and air. Once constructed, the device looks like several plastic plates with a repeating pattern of holes poked through them stacked on top of one another to form a sort of pyramid.

To give the illusion that it isn’t there, the cloak must alter the waves’ trajectory to match what they would look like had they had reflected off a flat surface. Because the sound is not reaching the surface beneath, it is traveling a shorter distance and its speed must be slowed to compensate.

Acoustic cloaking device hides objects from sound — ScienceDaily.


Abandoned underground ‘Mail Rail’

I recently discovered that the Royal Mail have an underground Rail Mail system beneath the streets of London, a fact im sure many people had no idea existed.  It launched in 1927 and was used to transport tonnes of post from one side of London to another, with stops at large railway hubs such as Liverpool Street and Paddington Station. After closing in 2003 it has remained unused but there are plans in place to turn it into a public attraction as part of the National Postal Museum.

My thoughts are concerned with the hidden and concealed nature of this transportation network beneath London and providing access and a means of secret circulation for the operatives.

Ride London’s abandoned underground ‘Mail Rail’ (Wired UK).