Device-to-device audio communication (think QR codes, but made out of sound) seems very underrated. Much better UX than QR codes or NFC because you don't have to worry about putting your phone in the exactly right place or pointing it in the right direction.

Anyone here with more detailed takes on this?

Should be outside of human (and dog) spectrum so it doesn't annoy anyone

But what if we want to hear cute AI-generated melodies that hide cryptographically encoded secrets?

I would love that. Nothing brings us more together than sounds, a tone of a voice and music