Physicists Hear High-Tech Whistle While They Work
When ultra-cold liquid helium-4 was squashed through an array of tiny apertures, a phenomenon occured in which the helium-4 repeatedly sped up, slowed down and vibrated. This produced a "quantum whistle" -- a whistling sound that went from high to low.
+ Play audio of quantum whistle
Image right: Dr. Richard Packard, U.C. Berkeley professor, left, and Emile Hoskinson, U.C. Berkeley graduate student, right, are shown with a cryostat insert, where the experiment was performed.