A Cone of Silence
City dwellers, rest easy. Engineers have designed a material that redirects sounds and could be used in buildings to shield them from noises. The sound-shielding material, which, if actually made, would be the first acoustic cloaking device, could also be useful in hiding military ships and other vessels from sonar.
Acoustic cloaking materials, which direct sound waves around an object so that they re-form on the other side with no distortion, do not exist in nature. But engineers led by José Sánchez-Dehesa at the Polytechnic University of Valencia, in Spain, have created a plan for making them, using alternating layers of two different materials. These materials would comprise arrays of sonic crystals–patterns of small rods made of aluminum or other materials that allow some sound waves to pass while blocking the passage of others.
MIT Technology Review
Sound shield: An acoustic cloak comprising alternating layers of sound-scattering materials should make objects invisible to sonar–and insulated from sound. In this computer-generated image, a cylinder (green circle) is coated with 200 layers of such a material, which was found to be the optimal design. Sound waves moving from left to right (their peaks and troughs are represented by red and blue lines) flow past the object and reform on the other side with no distortion.
Credit: New Journal of Physics
1.
Agent 86: “they can’t get rid of me. I know too much”
2. acoustics is a fascinating area. I am on 10 acres cut into a tall pine forest.
Opposite the road which makes the 4th side of this rectangle, there are open paddocks with cows whose mooing bounces out of the forest at me. very weird.
3. very often, research aimed at military application, results in completely different benefits for the civilian world (thank god), so we can hope for something better from this, than evading sonar detection.