Listening to an IPod or other portable digital music players at full volume using stock earphones for more than five minutes a day may cause hearing loss a new study finds. According to researchers at the University of Colorado at Boulder and Children's Hospital in Boston, the study also provides guidelines for listening to digital music devices safely. The guidelines indicate that the average person won't sufer hearing loss when listensing to music using earphones at 70 percent volume for up to 4.6 hours per day. The researchers state that genre of music listened to doesn't make any signicant difference in producing sound levels. The damage may occur when delicate hair cells in the inner ear, which convert mechanical vibrations of sounds to electrical signals that the brain interprets as sound, are exposed to loud music or sound over a period of time.