This site uses cookies. By continuing to use this site you agree to our use of cookies. To find out more, see our Privacy and Cookies policy.
Skip to the content

Share this

Free weekly newswire

Sign up to receive all our latest news direct to your inbox.

Physics on film

100 Second Science Your scientific questions answered simply by specialists in less than 100 seconds.

Watch now

Bright Recruits

At all stages of your career – whether you're an undergraduate, graduate, researcher or industry professional – brightrecruits.com can help find the job for you.

Find your perfect job

Physics connect

Are you looking for a supplier? Physics Connect lists thousands of scientific companies, businesses, non-profit organizations, institutions and experts worldwide.

Start your search today

Blog

Surround no sound?

By Tushna Commissariat

Image of the 3D acoustic cloak

A picture of the 3D acoustic cloak (left) and the cloak being tested in an anechoic chamber (right). (Courtesy: Physical Review Letters)

Invisibility cloaks seem to fascinate scientists and the public in equal measure, and every few months a novel design for some sort of metamaterial that cloaks either light or sound catches our eye, if you excuse the pun.

This week, we came across a group of researchers in Spain that claims to have designed, fabricated and tested the first “directional 3D acoustic cloak” that works for airborne sound. Previous designs of acoustic cloak work in water and air, but only if the sound propagates in 2D. Also, many cloaks only work within a narrow band of frequencies, limiting their uses.

However, José Sánchez-Dehesa, of the Polytechnic University of Valencia  and who has worked on many acoustic-cloak designs, and colleagues’ 3D cloak is made up of 60 concentric acoustically rigid rings that would surround the object to be cloaked – a sphere of radius 4 cm. According to their paper (published in Physical Review Letters), the distribution of concentric rings is determined by the direction in which the sound propagates. “The positions and major radii of the [rings] surrounding the sphere are determined such that they cancel the field scattered by the sphere,” according to the researchers, and these positions are “obtained through an optimization technique that combines a genetic algorithm and simulated annealing”.

The team printed a prototype of its cloak design using a 3D printer and tested it in an anechoic chamber. The researchers found that their “low-loss fabricated cloak” reduces the intensity of the waves scattered by the sphere by 90% at 8.55 kHz.

The team does acknowledge that the cloak is directional and narrow-banded, but says that improvements can be made. The scientists suggest that certain modifications could be made so that the cloak is both broadband and omnidirectional. They also say that cloaks for underwater operation could also be possible using this design, by introducing elasticity to the rings used.

This entry was posted in General and tagged , , . Bookmark the permalink.
View all posts by this author  | View this author's profile

Leave a comment

Your e-mail address will not be published. Required fields are marked *

Guidelines

  • Comments should be relevant to the article and not be used to promote your own work, products or services.
  • Please keep your comments brief (we recommend a maximum of 250 words).
  • We reserve the right to remove excessively long, inappropriate or offensive entries.

Show/hide formatting guidelines

Tag Description Example Output
<a> Hyperlink <a href="http://www.google.com">google</a> google
<abbr> Abbreviation <abbr title="World Health Organisation" >WHO</abbr> WHO
<acronym> Acronym <acronym title="as soon as possible">ASAP</acronym> ASAP
<b> Bold <b>Some text</b> Some text
<blockquote> Quoted from another source <blockquote cite="http://iop.org/">IOP</blockquote>
IOP
<cite> Cite <cite>Diagram 1</cite> Diagram 1
<del> Deleted text From this line<del datetime="2012-12-17"> this text was deleted</del> From this line this text was deleted
<em> Emphasized text In this line<em> this text was emphasised</em> In this line this text was emphasised
<i> Italic <i>Some text</i> Some text
<q> Quotation WWF goal is to build a future <q cite="http://www.worldwildlife.org/who/index.html">
where people live in harmony with nature and animals</q>
WWF goal is to build a future
where people live in harmony with nature and animals
<strike> Strike text <strike>Some text</strike> Some text
<strong> Stronger emphasis of text <strong>Some text</strong> Some text
WordPress Appliance - Powered by TurnKey Linux