In occupational noise, exposure is quantified as dose or Leq over a work shift. Which standard commonly defines acceptable daily exposure limits?

• A. ISO sound level measurements are used and assume no exposure limits.
• B. Only peak instantaneous levels are used.
• C. Noise exposure is not quantified.
• D. Exposure is dose or Leq over a work shift; OSHA PEL (90 dBA TWA) is a common reference.

Answer: (D)

Exposure to occupational noise is evaluated using energy-based metrics over the work shift, specifically dose or Leq (equivalent continuous sound level). Leq converts fluctuating noise into a single steady level that would deliver the same total energy, while dose compares the actual exposure duration at various levels to the permissible duration at those levels. The standard most commonly used to define acceptable daily limits is OSHA's permissible exposure limit, defined as 90 dBA as a time-weighted average over an 8-hour shift. This means that maintaining an 8-hour average at or below 90 dBA keeps you within the allowed daily exposure; exceeding it requires action to reduce exposure or provide protection. The other statements don’t fit because exposure is indeed quantified with these energy-based metrics, not just peak levels, and measurement standards do not imply there are no exposure limits.