Screenshot from video:  https://www.youtube.com/watch?v=wBY3Z4F0dxk

In this activity, we will use a vacuum pump to place a tube under vacuum that has a ping pong ball at one end. By breaking the seal on that side, the air will then rapidly rush back into the tube and push the ping pong ball to the other side of the tube. Because the ball is so light and moves through the vacuum without resistance, the air is able to push it very quickly to speeds faster than the speed of sound.

Williams, Chris, and Peter Rees. (2014). Supersonic Ping Pong/Ice Cannon [215] Mythbusters. Los Angeles, CA: Discovery.