These Scientists Have Created An Invisibility Cloak – For Sound Waves


All right, time to take out my wand and manage some mischief!

Scientists have developed a sort of invisibility cloak but it’s not like the one from Harry Potter so don’t get too excited…It’s basically a ‘cloaking’ technique that changes the impact of sound waves when they hit different objects so they don’t hit or reflect back from them. In that sense, these objects can be made “invisible” as far as acoustics are concerned.

The technique works by using an outer ring made of microphones and an inner ring of loudspeakers. The microphones act as audio sensors while the loudspeakers act as audio sources. As the microphones speak up the sound waves, a computer directs the speakers to adjust the acoustic field so it acts as if the object isn’t there and conceals it completely.

The researchers explained this in their paper, “This opens previously inaccessible research directions and facilitates practical applications including architectural acoustics, education, and stealth.” While the technique of hiding objects acoustically isn’t something new, this new real-time approach is far more practical and for a wider range as compared to the limited range of frequencies it was previously tested on. It also works in reverse; by making a non-existent object take space in a room by making certain sounds, is known as holography.

Till now, the researchers have been successful in using their system for working on 2D objects up to 12 centimeters in size and on a wide range of frequencies. In the future, they are hoping to scale up the technique to work with 3D objects with much larger size. “Our facility allows us to manipulate the acoustic field over a frequency range of more than three and a half octaves,” says geophysicist Johan Robertsson from ETH Zurich in Switzerland. This cloaking technology could be used in any field related to dealing with sound waves and for a wide range of scientific applications. The research has been published in Science Advances.


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