"Radio emissions were discovered by radio and plasma detectors on board the Cassini spacecraft as it passed over Saturn's rings during its arrival at the planet in July 2004.The tones are emitted as radio waves. Don Gurnette of the University of Iowa says his team reduced their frequencies by a factor of five to bring them into the range of human hearing. Gurnett says he was 'completely astonished' when he heard the musical notes.The tones are short, typically lasting between one and three seconds, and unlike the ethereal sliding tones associated with other cosmic processes, every one is quite distinct. The evidence suggests that each tone is produced by the impact of a meteoroid on the icy chunks that make up the rings."
NASA's quote on the file (which some suggest sounds like speech):
"A most intriguing file, we do not know what to make of it..."