The first thing that comes to mind when people talk about an invisibility cloak is usually something visual. However, scientists created one for sonar detection.
Science fiction commonly portrays cloaking devices as a complex technology that can bend light around an object to make it invisible. The device with purported cloaking abilities is not what most people expected. Once perfected, it could have practical applications that might surprise everyone.
Creating A New Material
Reports confirm that Penn State researchers made the discovery. Amanda Hanford, a research associate, led the team. Everyone in the group had to find a metamaterial that would function like the radar absorbent material painted on planes, which renders the aircraft invisible to ground-based radar.
However, the challenge was to come up with a new one that will work underwater against sonar. Nevertheless, it looks like they were able to create one successfully.
To showcase the progress of their work, the Penn State researchers decided to schedule a demonstration. The metamaterial invisibility cloak for underwater applications made its debut in Minneapolis, Minnesota, during the 175th Meeting of the Acoustical Society of America.
Experts note that most of the readily available acoustic metamaterials are specifically-designed to work outside the water. Doing the same underwater requires a different set of parameters due to how sound waves behave below the surface. It was exactly the challenge that the team wanted to overcome with their research.
Demonstration And Results
What the research team came up with is a pyramid-shaped structure that measures about three feet tall. It was visibly constructed out of perforated steel and what looks like an acrylic frame. It was then submerged in a tank while a hydrophone produced 7,000 Hz and 12,000 Hz acoustic waves. Receivers were then spaced around the tank to monitor the results.
Based on the readings, the reflected waves exhibited decreased amplitude after it bounced off the structure. Scientists admit that it is possible for the metamaterial to function as an invisibility cloak against sonar.
Far From Perfect
Most experts agree that the underwater invisibility cloak demonstration is still in the early stages. As it stands, it was just a static structure, inside a tank, and in a controlled setting. If only the demonstration was made on a real submarine in the ocean with real sonar thrown in, then the results will be more conclusive, and it will clarify if the metamaterial sonar deflector worked as intended.