A Canadian study has found that nearly 30% of teens have a condition called tinnitus, a ringing or buzzing in their ears. The condition could be a sign that their auditory nerves have been damaged, and could lead to hearing loss later in life. The World Health Organization has warned that 1.1 billion young people are at risk of hearing loss because of portable digital music players and damaging levels of sound at entertainment venues, such as electronic dance music festivals, where sound levels can top 120 decibels for hours. Other experts blame smartphones and warn that a major health crisis may be looming as these teens become adults. Experts say the best way to protect young ears is to apply the "60/60" rule: Keep the volume on the MP3 player under 60 percent and only listen for a maximum of 60 minutes a day.