Well, here's a noodle-scratcher to start your day with. Sprint has just sent out invites to an event on April 29, and it's being characteristically coy about what's going down. The carrier's chosen imagery and tagline leave little to the imagination though: this rodeo is all about audio, and our guess is that CEO Dan Hesse probably has some more to say about Sprint's HD Voice rollout. Sprint's been slowly rolling out the service (which it claims will provide "crystal clear" call quality to owners of compatible devices) in Kansas City, with Philadelphia and Baltimore to follow in the coming weeks. Hesse's ultimate goal is to get the whole nation flying under that HD Voice banner by July, and it probably won't be long before he steps on-stage to let us know how that's working out for him.