Normative Data of Extended High Frequency Audiometry in Normal Hearing Subjects with Different Aged Groups

Background/Objectives: Conventional audiometry assesses hearing in the frequency range of 250-8000 Hz, while humans can detect sounds from 20 to 20,000 Hz. Hearing sensitivity above 8000 Hz can be assessed through "Extended high-frequency audiometry (EHFA)", which is useful for early detection and monitoring of hearing loss and counseling for tinnitus patients. Despite its usefulness, age significantly affects hearing sensitivity. Currently, there are no standard hearing thresholds in the EHF range categorized by age groups in Thailand. In this study, the aim was to determine normative EHFA data across different age groups in a healthy Thai population. Methods: This study included 134 participants aged 18-70 years, categorized into five age groups. All participants had normal hearing thresholds and type A tympanograms bilaterally. Following this, EHFA measurement was performed. Results: Across all age groups, there was an observed increase in median hearing thresholds as age increased. In comparison, no significant difference in median hearing thresholds was found between individuals aged 18-30 and >30-40 years. However, those over 40 years had significantly higher median thresholds across all frequencies compared to those under 40 years (p < 0.05). Based on these findings, we propose two new subgroups of 18-40 years and >40-70 years. Median hearing thresholds for those aged 18-40 was ≤20 dB HL across most frequencies, except at 16,000 Hz (30 dB HL). In the >40-70 age group, thresholds ranged from 20 dB HL at 9000 Hz to 70 dB HL at 14,000 and 16,000 Hz. However, no significant differences were found in hearing thresholds between sexes and ear sides. Conclusions: In this study, normative EHFA data were established for healthy Thai adults, appropriately divided into two groups (18-40 and >40-70 years) for clinical use. Further studies with more participants per age group are also needed to validate the results.