美国一项调查显示，近1/5的美国青少年存在不同程度的听力损伤，这一数字比20年前上升了约5个百分点。研究人员将此现象归咎于青少年使用iPod等音乐播放器时音量过大、时间过长。

    Portable music players and an increased exposure to live music has led to a surge in hearing loss in teens, recent research suggested. 

    The number of teenagers experiencing hearing problems has gone up by nearly a third in the last 20 years in America, according to the report. Between 2005 and 2006, one in five adolescents suffered some form of hearing loss, the study found. This was 6.5 million more than in an earlier survey conducted between 1988 and 1994, representing an increase of approximately 30 percent. 

    The root causes for the increase are unknown, although the scientists believe that exposure to loud noise such as amplified music may be one explanation. Josef Shargorodsky, of Brigham and Women’s Hospital, Boston, examined the two databases to see if there was a comparable degree of hearing loss in the different timeframes. 

    Between 1988 and 1994, there was a 14.9 percent prevalence of hearing loss, which rose to 19.5 percent in the more recent study of 12 to 19 year olds. The majority of the hearing loss was slight, although the number of cases of mild or worse hearing loss was 77 percent higher in the more recent survey.