The popularity of personal listening devices might have an unpopular long-term impact. Hearing expert Barbara McLay at the University of Missouri warns that people who will get things such as I-pods or MP3 players for Christmas, and spend hour after hour listening to them, can suffer long-term hearing loss. She says direct delivery of music into the ear eventually can cost a person the ability to understand other people’s speech. She says if people three feet from you can hear what you’re listening to, it’s too loud, and can endanger your hearing in the long term.