That's a sound level that's equivalent to the measures that are made at rock concerts. And it's enough to cause hearing loss after only about an hour and 15 minutes.

Insert earphones can boost the signal by as much as six to nine decibels. That's about the difference between the sound of a vacuum cleaner and a motorcycle. It's a significant difference.

I have an audiologist friend at Wichita State University who actually pulls off earphones of students he sees and, in the interest of science, asks if he can measure the output of the signal going into their heads. He found that often students were listening at 110 to 120 decibels.

We're seeing the kind of hearing loss in younger people that's typically found in aging adults.

If music listeners are willing to turn the volume down further still and use different headphones, they can increase the amount of time that they can safely listen.

That's the difference in intensity between the sound made by a vacuum cleaner and the sound of a motorcycle engine.