One tune-fueled cardio session could be enough to damage your ears. Researchers at Ghent University in Belgium found that after 60 minutes of listening to pop-rock on earbuds or headphones (at 50 to 100 percent of an iPod's maximum volume), subjects suffered significant short-term hearing deterioration. Over time, repeated exposure to loud music can lead to permanent damage. These days hearing loss is becoming more and more common in young people.
Turn down the volume. If you exercise in a noisy setting, try sound-isolating headphones. They block ambient noise, so you can hear your music at a lower volume.