Researchers have creating a cloaking device that redirects approaching waves around an object without scattering the wave energy, essentially making it invisible to devices like sonar, according to a statement from the Acoustical Society of America.
Amanda Hanford, of Pennsylvania State University, will describe the physics behind the cloaking device, until now only the stuff of sci-fi movies, at the annual meeting of the society, which runs through Friday in Minneapolis.
Hanford and her fellow researchers engineered a metamaterial that would allow sound waves to bend around an object as if it was not there, according to the ASA statement. For the device to work, the unit cell of the metamaterial must be smaller than the acoustic wavelength in the study.
“These materials sound like a totally abstract concept, but the math is showing us that these properties are possible,” Hanford said in the statement. “So, we are working to open the floodgates to see what we can create with these materials.”
According to R&D magazine, most of the acoustic metamaterials have been designed to deflect sound waves in air, but not water. Penn State researchers, though, opted to see if they could move the technology forward and try to deflect sound waves underwater.
R&D wrote that since water is denser and less compressible than air, it limited engineering options.
The Penn State researchers eventually created a three-foot-tall pyramid out of perforated steel plates. The team then placed the structure on the floor of a large underwater research tank.
A source hydrophone inside the tank produced acoustic waves between 7,000 hertz and 12,000 hertz, and several receiver hydrophones around the tank monitored reflected acoustic waves, the statement explained.
TechCrunch reported that, in testing, the resulting echoes in the water suggested that the sound waves did not bounce off or around the material, meaning the new material was invisible to sonar.
“Obviously this technology is still in its early stages and the material does not make the objects invisible but just very hard to detect in underwater situations,” TechCrunch wrote. “However, the fact ship captains could soon yell ‘Activate the cloaking device’ as evil, laser-toting dolphins appear on the horizon should give everyone a bit of cheer.”