Metamaterials make 3D acoustic cloaking device

The acoustic cloaking device works in all three dimensions, no matter which direction the sound is coming from or where the observer is located, and holds potential for future applications such as sonar avoidance and architectural acoustics. The study appears online in Nature Materials.

‘The particular trick we’re performing is hiding an object from sound waves,’ said Steven Cummer, professor of electrical and computer engineering at Duke University in North Carolina. ‘By placing this cloak around an object, the sound waves behave like there is nothing more than a flat surface in their path.’

To achieve this, Cummer and his colleagues turned to metamaterials, the combination of natural materials in repeating patterns to achieve unnatural properties. For the new acoustic cloak, the materials manipulating the behaviour of sound waves are 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 resemble a pyramid.