Headphones

Headphones can be dangerous because they can cause hearing loss. By having headphones that predict the length of time that headphones can be at such volume, can limit the duration of loud sounds being played through the head phones.

Directional Speakers
The speakers in the headphone can tilt away from the center of the ear drum as the volume is turned up. This can prevent hearing loss. This will work well in headphones that fully cover the ear, not the buds.