Ping pong balls used as #Helmholtz #resonators offer a low-cost solution for blocking low-frequency urban #sounds, which are difficult to block with traditional methods. Researchers from the University of Lille and the National Technical University of Athens found that combining multiple Helmholtz resonators increased the range of sound #frequencies that could be absorbed. This affordable and accessible solution could have applications beyond sound insulation, such as sound focusing and manipulation, according to physicist Robine Sabat.

https://www.sciencealert.com/scientists-find-an-awesome-practical-use-for-ping-pong-balls