The present study was conducted to develop a normal aging curve in hearing of Thai people. The subjects were 805 males and 1110 females ranging in age from 7 to 89 years. Audiometric hearing threshold testing was performed at the frequencies of 1, 2, 4 and 8 kHz. Subjects with no evidence of hearing impairment were selected for hearing level analysis. The accepted subjects comprised of 1298 ears in males and 1818 ears in females with normal hearing. A normal aging curve of hearing level at each frequency was established by calculating the 25^th, 50^th, and 75^th percentiles for each age group. The hearing threshold level gradually increased with age and rapidly over 50 years in both sexes, in particular at 8 kHz and 4 kHz. The results showed significant correlations between the hearing level and age. There were sex differences in hearing level at the 4 kHz from the age of 40. This normal curve established from subjects with no evidence of hearing problems may be useful for monitoring hearing levels of Thai people.

Keywords: Hearing level, Age-related, Thai people