As an "audio sharing service," Google Tone is probably not what you think. It has nothing to do with music, for one, or for sharing in any sense to which we're accustomed. It's based on sound, but not sound that we as humans can hear. There are no addresses, digital handshakes, or encryption keys. In the usual sense of network security, it's spectacularly, comically naked, but shutting out eavesdroppers is as easy as closing a door or window.
Tone, which is now available as a Chrome browser extension, is limited to pretty much one task: At the press of a button, it will broadcast the URL (as encoded tones) currently being viewed on the broadcaster's computer to every other computer within earshot that also has the extension installed. Using regular old microphones and speakers, Tone allows groups of computers to talk—and it is approximately as private as a conversation between humans.
"The initial prototype used an efficient audio transmission scheme that sounded terrible, so we played it beyond the range of human hearing," write Alex Kauffmann and Boris Smus on the Google Research Blog. "However, because many laptop microphones and nearly all video conferencing systems are optimized for voice, it improved reliability considerably to also include a minimal DTMF-based audible codec. The combination is reliable for short distances in the majority of audio environments even at low volumes, and it even works over Hangouts."
"The first version was built in an afternoon for fun (which resulted in numerous rickrolls)," Kauffmann and Smus add, "but we increasingly found ourselves using it to share documents with everyone in a meeting quickly, to exchange design files back and forth while collaborating on UI design, and to contribute relevant links without interrupting conversations."
This is either a totally great idea or a terrible one.