dr. richard litchinstein. >> this may be the next thing people need to be aware of. >> reporter: in 2004, 16 people in the u.s. were injured while waking and wearing headphones. by last year, that number had tripled to 47. of the 116 people hit in the past seven years, 81 died. >> if you're plugging up your ears from alarms, sirens, and horns, you're going to put yourself at risk for injury and death. >> reporter: more than half the accidents involve pedestrians hit by trains. according to the study, it's not just the noise that's the problem. it's the distraction of using the device. despite the dangers, pedestrians we spoke to say they still do it. >> i have tunnel vision. when i walk around, i like to block things out. >> reporter: though some try to be safer. >> i only use one ear sometimes so i can hear what's going down. >> reporter: bumping down the volume could save your life. and the majority of those injured are males under the age of 30. reporting live for wjz eyewitness news. >> thank you. more than a quarter of the injury cases, the train or car sounded an alarm or horn to tr