There are some projects which try to make the audio sound pleasant, like birdsong or water. And there are fountain codes which continually stream data and you c

There are some projects which try to make the audio sound pleasant, like birdsong or water. And there are fountain codes which continually stream data and you can start picking up the transmission at any point and as long as you get enough of it you can recreate the message. And of course compared to wifi you don't need to 'join' a network or broadcast anything to listen. I'm imagining something like this at a train station or airport, continually broadcasting schedule and delay information which you could pick up with an app and a microphone and no internet access. Like a drinking fountain for information something you go to, or maybe pervasive background noise.