Chances are, if your son or daughter has a smartphone, tablet or iPod, they have listened to music through headphones or earbuds. With more and more youngsters doing just that, many doctors across the U.S. are seeing an uptick in the number of teens with hearing loss.

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The World Health Organization (WHO) has warned that 1.1 billion young people are at risk of hearing loss because of personal audio devices and by certain entertainment venues where music tops 120 decibels for an extended period of time.

"There is no doubt that listening to loud music for an extended period of time is going to cause some damage," said Dr. Allison Lavene, audiologist at Children's Specialized Hospital. "Loud noise with extended exposure can damage the hair cells that are in the inner part of the ear. If they are permanently damaged, they can't be repaired."

Generally, 85 decibels or softer is considered safe, but that's tricky because without a sound meter parents don't know if their child is listening that softly or not.

"Basically, if a child is sitting a few feet away from you and you can hear their music coming out of their earbuds or headphones, then it is too loud," Lavene said. "Eighty-five decibels can probably be compared to the sound of a blow dryer or a food processor."

According to the WHO's report that was issued in February, if a person is exposed to 95 decibels of sound, damage can occur within four hours. It would only take two hours of exposure at 100 decibels for damage to occur. Above 100 decibels only takes one hour of exposure to cause damage.

So what are some things parents can do to help protect their child's hearing?

Experts agree that a good rule of thumb is the "60/60" rule - to keep the volume under 60 percent and only allow them to listen for 60 minutes a day. Many smartphones and devices have parental control settings which allow for lower volumes to be set and locked into place with a password. For small children who are attending any event where sound is expected to exceed the recommended decibel levels, it is recommended that parents buy ear protection.

Click here for more recommendations from WHO.