And what if we could mount these directional speakers directly on someone’s head! Then we could reduce the volume a lot so it’s even quieter to neighbors. Maybe use some sort of physical bell or cup shape to direct it right into someone’s ears without ultrasonics (for cost reasons). Then we might save enough that we can use 2x speakers to get L/R audio streams.
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.
(Am fairly certain they aren't great if you are going for audiophile level reproduction - but from a safety perspective, they let you hear your environment - note, I have personally never tried them)
Quality isn't amazing, but it's acceptable and it isn't like you'd be enjoying a high quality audio experience with wind rushing past your ears using normal headphones, anyway.
Also beats getting hit by a car that you didn't hear.
I'm a runner not a cyclist, but I use AfterShokz headphones. The sound quality is suprisingly good, more than adequate for listening to music and podcasts when out :)
For personal safety though, they win hands down. I can hear cars and people easily and I'm much more aware of surroundings. Downside is though that if you are running down a busy road, the sound of cars can override the sound of your audio but for me, that's an acceptable trade off.
I have aftershokz aeropex. If you are hoping for studio monitors you're going to be disappointed. If you just want to listen to podcasts or "workout music" then I think they are great. I use mine way more often around the house than I expected that I would.