Comment by germinalphrase

To address your point rather than your sarcasm: headphones are unsafe while cycling because they block environmental sounds (though it’s true that music from a speaker can impact attentional blindness. There is also the shared experience of listening to music with another person. The ability to create a “music bubble” around you without disturbing others satisfies both parties.

Ultrasonic speakers aren’t even exotic tech. I first encountered one in a museum at least ten or fifteen years ago.