CONE OF SILENCE (UNDERSEA EDITION): Device could make underwater objects appear invisible to sonar.

The device makes sound waves scatter around an object making it invisible to sonar detection.

In order to achieve this, the researchers used a “smart” material with special properties.

The researchers have outlined their work at a major scientific meeting in Minneapolis, US.

When a ship sends out a signal to detect objects in the ocean or to map the sea floor, the signal bounces back in a way that makes it appear as if the cloaked object isn’t there at all.

Amanda Hanford and her team at Pennsylvania State University in State College designed a 90cm (3ft) -tall pyramid out of perforated steel plates that could do just that.

The smart “metamaterial” they developed for use in the “cloak” forces sound waves to spread their energy around the object, making it undetectable to underwater sensors.

Interesting, although over the last few years real progress has been made in non-acoustic methods of detecting large underwater objects, such as nuclear missile submarines.