Figure 1.

Pure-tone average for all ages at speech frequencies (0.5, 1, 2 and 4 kHz) (A: total participants; B: male participants and C: female participants). The full lines indicate the hearing thresholds of left ears, and the dotted lines indicate the hearing thresholds of right ears. Bars indicate ±1 SD. ‘20 years’ old represents people aged 18–25 years old, ‘30 years’ old represents people aged 26–35 years old, ‘40 years’ old range is 36–45 years old, ‘50 years’ old range is 46–55 years old, ‘60 years’ old range is 56–65 years old, ‘70 years’ old range is 66–75 years old, ‘80 years’ old range is 76–85 years old and ‘90 years’ old range is 86–98 years old. PTA, pure-tone average.