Possible cause is Blockage of ear by foreign body or wax buildup. Action to take Consult your pediatrician who will examine the ear, using a lighted instrument called an otoscope, and remove the blockage. Action to take Call your pediatrician who will examine the ear and treat the child appropriately. Action to take Hearing loss due to pressure change usually clears up by itself. If there's no improvement in 2 or 3 days, call your pediatrician.
Possible cause is Neurological disorder.
Action to take Consult your pediatrician, who will examine the child to determine whether he needs treatment. Preventing injury from headphones Children and teenagers often prefer to listen to music through headphones linked to a radio, stereo, or portable tape player. Kept at a volume similar to normal speech, headphones may do no harm. But if youngsters turn up the volume to block out external noise, they subject their ears to an assault that can cause permanent hearing loss. If others in the room can hear sound while the child is wearing headphones, the volume is at an unsafe level and should be turned down.