Look out Romulans; humans are currently working on a cloaking device.
“Researchers at Penn State University created an underwater ground cloak capable of redirecting sound waves so objects appear concealed.
“The cloak uses a metamaterial that holds properties not found in nature, allowing waves to bend around an object as though it were not there.
“To test this, researchers created a three-foot-tall pyramid out of steel plates and placed it underwater. Producing sound waves with a hydrophone, researchers found the metamaterial redirected the waves in a way to make the pyramid appear invisible.”
Source: KIII TV