What does the 8-hour Time-Weighted Average (TWA) represent in occupational noise exposure?

• A. The average sound level over 24 hours
• B. The average exposure over an 8-hour work shift
• C. The peak sound level in a given moment
• D. The maximum daily exposure

Answer: (B)

An 8-hour time-weighted average is the energy-equivalent average sound level a worker is exposed to over an 8-hour work shift. It combines all the varying noise levels during the day into a single value that represents the total acoustic energy received in that period. Because sound energy accumulates with both level and time, louder periods contribute more to the TWA, but extended quieter periods also affect the average. This measure is used to assess compliance with occupational noise limits and is compared to the 8-hour exposure threshold, not to a 24-hour average or to a peak moment.