Extended High-Frequency Audiometry in Early Detection of Noise-Induced Hearing Loss in Occupational Settings

Abstract

Objective: This study investigated the effect of noise exposure on extended high-frequency audiometry (EHFA) thresholds in an occupational setting. This study aimed to determine whether EHFA can provide insights into early cochlear changes that are undetectable through conventional methods and whether EHFA is more pronounced among workers exposed to higher noise levels.

Methods: A retrospective, quantitative design was employed to analyze audiometric data from 180 employees across categories of three occupational noise exposure (<85, 85-104, and ≥105 dBA, A-weighted). Participants underwent conventional and EHFA, with thresholds measured from 500 to 20,000 Hz. Stratified random sampling was used to select individuals with normal thresholds at 500 to 4000 Hz (<25 dB HL). Multivariate analysis of variance and logistic regression were used to evaluate the effects of noise exposure, age, and years of service on EHFA thresholds.

Results: The conventional audiometry thresholds were found between -10 and 50 dB HL, and the EHFA range was between -10 and 100 dB HL. The hearing threshold patterns were similar across the noise categories. No significant differences were observed in conventional audiometry and EHFA based on noise exposure categories (P = 0.511) or years of service (P = 0.745). However, significant associations with age were identified at 6000 Hz, 8000 Hz, and across all EHFA thresholds (P < 0.05).

Conclusion: EHFA demonstrated limited sensitivity in differentiating noise-induced hearing loss across noise exposure categories, potentially reflecting the effectiveness of the hearing conservation program implemented. Age emerged as a significant factor influencing thresholds at high frequencies, highlighting the importance of considering age in EHFA.

Keywords: audiometry; hearing loss; noise-induced; occupational exposure.

Figure 1

Patterns of distribution of mean thresholds obtained on conventional audiometry between the noise categories.

Figure 2

Box plots showing pure-tone air conduction thresholds in decibel hearing level (dB HL) by noise exposure category for conventional audiometric frequencies.

Figure 3

Patterns of distribution of mean thresholds attained on extended high-frequency among the noise categories.

Figure 4

Box plots showing pure-tone air conduction thresholds in decibel hearing level (dB HL) by noise exposure category for extended high-frequencies. No response values were substituted with 5 dB HL above the audiometer output.

Figure 5

Patterns of distribution of maximum thresholds attained on conventional audiometry and extended high-frequency for the noise exposure categories.

Figure 6

Frequencies with absent thresholds at maximum intensities (N = 180). Max intensities across 11,500–20,000 Hz; 95 dB HL for 11,500 Hz, 90 dB HL for 12,500 Hz, 80 dB HL for 14,000 Hz, 60 dB HL for 16,000 Hz, 30 dB HL for 18,000 Hz, and 15 dB HL for 20,000 Hz.