A noise dose of 100% marks the daily exposure limit, computed as a time-weighted average

Occupational noise exposure is quantified as a noise dose: the percentage of the allowable daily exposure a worker has accumulated. A dose of 100% or more means the worker has reached or exceeded the NIOSH REL for the day. The dose is derived from the Time Weighted Average (TWA) — the noise level averaged over the shift (usually 8 hours), which accounts for both how loud each exposure is and how long it lasts. Because dose integrates level and duration, brief very-loud exposures and long moderate ones can produce the same dose. Workers whose dose exceeds 100% must be enrolled in a hearing loss prevention program.

Examples

A dosimeter reading 100% at the end of a set means the engineer hit their full daily limit. Two hours at 91 dBA and eight hours at 85 dBA each represent a full 100% dose under the 3-dB rule.

Assessment

Define what a noise dose of 100% signifies, and explain how TWA lets a short loud exposure and a long quieter one yield the same dose.