Which frequencies are used to determine STS thresholds?

• A. 2,000 Hz, 3,000 Hz and 4,000 Hz
• B. 500 Hz, 1,000 Hz and 2,000 Hz
• C. 6,000 Hz, 8,000 Hz and 10,000 Hz
• D. 125 Hz, 250 Hz and 500 Hz

Answer: (A)

STS thresholds are determined by looking for a significant change in hearing sensitivity at specific frequencies in the same ear, using the worker’s baseline audiogram for comparison. The chosen frequencies—2,000 Hz, 3,000 Hz, and 4,000 Hz—cover the mid-to-high range where noise-induced changes typically appear and are most relevant for understanding speech. By averaging the thresholds at these three frequencies, examiners have a standardized measure to detect a real shift in hearing, which can trigger protective actions under a hearing conservation program. Other frequency ranges (like the very low or very high ends) aren’t used in this standard calculation because they’re less consistently affected by noise exposure or are more variable, so they wouldn’t provide the reliable trigger needed for STS determination.