Under OSHA regulations, a standard threshold shift on an annual audiogram is defined as a change in hearing threshold relative to baseline of an average of 10 dB or more at which frequencies?

• A. 500, 1000, and 2000 Hz
• B. 1000, 2000, and 3000 Hz
• C. 2000, 3000, and 4000 Hz
• D. 500, 1000, 2000, and 3000 Hz

Answer: (C)

OSHA assesses a standard threshold shift by looking at the average hearing threshold change at the higher frequencies most affected by noise, specifically 2000, 3000, and 4000 Hz. If the average threshold in an ear worsens by 10 dB or more compared with the baseline audiogram, that's considered a standard threshold shift. These particular frequencies are where noise-induced damage tends to show up first, so using the 2000–4000 Hz range reliably detects early shifts before other frequencies are involved. The calculation is done for each ear separately.

The other sets of frequencies don’t match OSHA’s method: including lower frequencies like 500 Hz or 1000 Hz or adding extra frequencies (such as four frequencies) isn’t how a standard threshold shift is defined.