Kids are famous for rising the audio to 11 just for fun.

I am not writing about youngsters and rock but toddlers and kids listening to walkman/mp3-player/whatnot that for a shorter or longer time raises the audio volume to hearing damaging levels.

Why not create headphones that are limited in themselves. Electronics it them limit the amount of energy allowed to push through. Since the mechanics of the ear phones are known it shouldn’t be too difficult.