Extended High-Frequency Audiometry (9-20 kHz) in Civilian Pilots.

INTRODUCTION: The greater sensitivity of extended high-frequency audiometry (EHFA) than conventional audiometry (CA) for identifying early changes in hearing has been well documented in previous literature. However, no studies about EHFA were conducted on civilian pilots. The aim of this study was to investigate the usefulness of EHFA as an assay to evaluate civilian pilots' hearing status. METHODS: An observational cross-sectional study was conducted on 134 civilian pilots (case group) and 101 subjects without noise exposure (control group). All of the subjects underwent CA (0.25-8 kHz) and EHFA (9-20 kHz). The potential of EHFA for identifying early changes in hearing was assessed. RESULTS: The two audiometric tools both showed significantly higher hearing thresholds in the case group for most of the frequencies tested, but the differences were more obvious for EHFA. Compared with the control group, the average thresholds in the case group increased 3.15 dB at CA and 7.83 dB at EHFA for age 20-29.The number was 2.37 dB and 990 dB for age 30-39; 3.80 dB and 8.19 dB for age 40-49; and 10.84 dB and 16.86 dB for age 50-59. There were 74.6% of pilots who had hearing loss in at least in one ear and at one frequency in CA and 94.8% at EHFA. Significant differences in EHFA were observed also between pilots and their controls with normal hearing thresholds at CA. CONCLUSIONS: EHFA is more sensitive than CA and could be useful in detecting subclinical changes of hearing in civilian pilots.