Hearing Threshold of Korean Adolescents usage period of personal music players ranged from 1 to 3 years in 237 students (48.4%), less than 1 year in 108 (22.0%), 3 to 5 years in 93 (19.0%), and more than 5 years in 24 (4.9%) (Table 2). We found that 399 students (81.4%) used mainly earphones (insert type), whereas only 53 (10.8%) used headphones (supra-aural type) and 10 (2.0%) used Table 3. Distribution of the Subjects according to Transducer and Type of Personal Music Players Used Tool used on listening Type of personal music players Not used Earphone Headphone Speaker Not used MP3 player Cassette tape recorder CD player Computer No (%) 28 (5.7) 399 (81.4) 53 (10.8) 10 (2.0) 28 (5.7) 382 (78.0) 20 (4.1) 22 (4.5) 38 (7.8) speakers. The most common type of personal music player was the MP3 player, used by 382 students (78.0%). In addition, 38 students (7.8%) used computers, 22 (4.5%) used CD players, and 20 (4.1%) used cassette tape players (Table 3). In reviewing the results of hearing tests, we found that the means of hearing threshold and the hearing level at 4 kHz in male students were 16.4 ± 8.4 dB and 10.8 ± 8.7 dB, respectively, in the right ear, and 14.7 ± 8.3 dB and 9.2 ± 7.7 dB, respectively, in the left ear. The means and hearing level at 4 kHz in female students were 12.7 ± 8.0 dB and 7.9 ± 8.4 dB, respectively, in the right ear, and 11.0 ± 8.0 dB and 6.8 ± 7.7 dB, respectively, in the left ear. Male students had significantly higher hearing thresholds in both the left and right ears than female students (Fig. 1). In the subject population overall, the means and the hearing level at 4 kHz were 13.9 ± 8.3 dB and 8.9 ± 8.6 dB, respectively, in the right ear, both significantly higher than their respective levels, whereas 10.5 ± 5.7 dB and 7.6 ± 8.6 dB, in the left ear, respectively (Fig. 2). Hearing thres- hold level in both ears was significantly higher in students Fig. 1. Hearing threshold at 4 kHz and means according to gender. *p < 0.05. Fig. 3. Hearing threshold at 4 kHz and means according to age. *p < 0.05. Fig. 2. Hearing threshold at 4 kHz and means according to side. *p < 0.05. Fig. 4. Hearing threshold at 4 kHz and means according to daily use time. Yonsei Med J http://www.eymj.org Volume 50 Number 6 December 2009 773