Generally, many auditory health organizations recommend that the ideal noise level for a child is about 70 decibels, and that volumes should never exceed 85 decibels. (Anything above 85 decibels is deemed dangerous, and could result in hearing loss or damage.) Most adult headphones peak at about 115 decibels, which is why it's important to use a dedicated solution for your child. The limit is a limit too, not a guide, so always aim to play music a little quieter if you can.