Even with headphones that effectively limit maximum sound, parents need to watch how — and for how long — children use them.

"Eighty-five decibels isn't some magic threshold below which you're perfectly safe and above which your ears bleed," said audiologist Brian Fligor.

That's why audiologists offer these listening tips:

• Keep the volume at 60 percent.

• Encourage your child to take off the headphones every hour to allow the hair cells in the inner ear to rest. Nonstop listening can eventually damage the hair cells.

• Take this test: If you are an arm's length away, your child wearing headphones should still be able to hear when asked a question.

If they can't hear you, "that level of noise is unsafe and potentially damaging," said Dr. Jim Battey, director of the National Institute on Deafness and Other Communication Disorders.

New York Times