When must an audiometry baseline be established according to NIOSH standards?

Establishing an audiometry baseline within 30 days of noise exposure is crucial to effectively monitor hearing health and detect any changes over time related to occupational noise exposure. By setting the baseline during this period, hearing conservation programs can accurately assess an individual's hearing capabilities before any significant noise exposure potentially causes auditory changes. This timing allows for the implementation of necessary precautions, such as hearing protection, if needed.

The other options suggest different timings for establishing baselines that could either occur too early or late to be effective. For instance, establishing a baseline before any noise exposure does not account for the individual's pre-existing hearing levels and might not reflect occupational influences. Setting the baseline at the first duty station or after 60 days of exposure could potentially miss early warning signs or lead to insufficient monitoring during critical exposure periods, undermining the effectiveness of hearing conservation efforts.