Engineers have demonstrated the world's first three-dimensional acoustic cloak. The new device reroutes sound waves to give the effect that both it and anything beneath it are not there. It works in all three dimensions, no matter which direction the sound is coming from or where the observer is located, and holds potential for future applications such as sonar avoidance and architectural acoustics.
This video demonstrates the difference in how sound waves act with and without the acoustic cloak in their path. The red and blue lines represent the high and low points of the sound waves. As they return to the top of the frame, notice how the profile of the sound waves on the left with nothing in their way closely matches the profile on the right after interacting with the acoustic cloak. In contrast, the center trial shows the deformation of sound waves that occurs with an uncloaked sphere in their path.