Myung Gu Kim, et al. aged 13, 14, and 15 years than in students aged 17 and 18 years (Fig. 3). Although there was no relationship between hearing threshold and daily use of portable music players (Fig. 4), we observed significant increases in students who had used these players for more than 5 years (11.7 ± 10.3 dB and 9.8 ± 12.8 dB at 4 kHz for the left and right ears, respec- tively) compared with students who did not use personal music players (7.2 ± 4.3 dB and 4.8 ± 4.7 dB, respectively) (Fig. 5). Hearing threshold at 4 kHz in the right and left ears was significantly higher in the 24 students with cumulative usage >15 hr × years (11.7 ± 10.5 dB and 11.0 ± 14.6 dB, respectively) than in the 466 students with < 15 hr × years cumulative usage (8.7 ± 8.5 dB and 7.5 ± 7.5 dB, respectively; p < 0.05) (Fig. 6). Subjects listening to music using speakers were found to have means and hearing levels at 4 kHz in the left (5.6 ± 4.1 dB and 5.0 ± 6.0 dB, respectively) and right ears (5.2 ± 3.7 dB and 1.9 ± 2.6 dB, respectively) that were signifi- cantly lower than those of subjects of using earphones or headphones (Fig. 7). Subjects who used computers to listen to music were found to have satisfactory means and hearing levels at 4 kHz in the right (9.4 ± 7.5 dB and 7.4 ± 5.3 dB, respectively) and left ears (7.8 ± 6.1 dB and 4.7 ± 6.0 dB, respectively); these numbers were significantly different compared with subjects using other methods of listening to music (Fig. 8). DISCUSSION Hearing loss is associated with difficulties in usual daily life. Children and adults with hearing loss may have limited social activities, have a reduced quality of life, or develop psychological problems, including feelings of isolation and exclusion, as well as depression and cognitive disorders.10 In approximately one-half of individuals with hearing loss problems, these losses are at least partially related to short Fig. 5. Hearing threshold at 4 kHz and means according to total use period. *p < 0.05. Fig. 7. Hearing threshold at 4 kHz and means according to type of headphone. *p < 0.05. Fig. 6. Hearing threshold at 4 kHz and means according to cumulative use period. *p < 0.05. Fig. 8. Hearing threshold at 4 kHz and means according to type of personal music player. *p < 0.05. 774 Yonsei Med J http://www.eymj.org Volume 50 Number 6 December 2009