Buzz means "a low continuous humming sound like that of a bee" or "speculative or excited talk or attention relating especially to a new or forthcoming product or event."
It's not just bees, or air conditioners, that generate buzz anymore. Before buzz came to mean "excited attention," it meant "rumor or gossip," likely from the murmuring sound of people whispering suggestions to one another. Now it might even be said to connote electronic buzzing, as when a smartphone vibrates with notifications.