University physicists have created a freezer that can keep ice cream cold using sound waves. This isn’t just a “cool” trick—it can also help the environment.

On a lazy summer day when you’re enjoying a cold and refreshing ice cream cone, you’re probably not thinking about how it stayed cold before it ended up in your hand. But physicists at Penn State University are.

They are using a process called thermoacoustics to create a “green” chiller. “Thermoacoustics involves essentially using sound to produce cooling,” says Bob Smith, research engineer at the Penn State Applied Research Lab. “It’s the interaction between sound and heat.”

The patented prototype “thermoacoustic chiller,” which was put on display at a Ben & Jerry’s scoop shop in New York City on Earth Day and successfully kept the ice cream cold, has a container that holds a loudspeaker and a canister of helium. The sound waves from the loudspeaker cause the helium gas to compress and expand.

More here.