My helper started useing a Sony Walkmen portable CD music player with the earpiece.I'm not sure whether to allow this or not yet.It could be a safty issue if he is not concentrating on the task he is doing. He also forgot to label a panel for a central air conditioning job we did recently and I wonder if it was related to the tunes in his ear. I like rock & roll, but, I myself can't concentrate with music blaring in the background.