... At the heart of the system is sound -- a 190-decibel [pulse/wave?] that fluctuates some 100 times per second. That expansion and compression creates pockets of cold and warm [gas, then the heat gets vented out of the system].
I could do with listening to some of that this summer. Though according to Wikipedia: "eardrums pop at 190 to 198 dB", so it's probably not such a good idea.
Apparently, "the Penn State thermoacoustic chiller uses helium gas instead of chemical refrigerants".