Noise Exposure Dose And Time-Level Tradeoffs
Canonical Definition
Noise exposure dose is the accumulated fraction of a stated reference exposure produced by one or more sound levels over time. A valid result identifies the frequency weighting, detector or averaging method, criterion level, exchange rate, threshold, measurement range, integration period, microphone position, and exposure model.
The Minimum Record
| Field | Why it matters |
|---|---|
| weighting | dBA, dBC, and dBZ do not represent the same frequency content |
| averaging or detector | LAeq, TWA, maximum, and peak answer different questions |
| criterion and exchange rate | the time-level relationship changes with the selected model |
| threshold and range | quiet intervals can be excluded and loud events can overload the instrument |
| time and repetition | dose accumulates across every run and other exposure during the period |
| ear position | a competition sensor elsewhere in the cabin is not the listener's exposure measurement |
Do Not Merge Different Reference Systems
- NIOSH occupational REL: 85 dBA over eight hours with a 3 dB exchange rate.
- OSHA occupational PEL: 90 dBA over eight hours with a 5 dB exchange rate; the hearing-conservation action level uses a separate regulatory calculation.
- WHO recreational reference: an adult safe-listening allowance based on 80 dB for 40 hours per week with a time-level tradeoff.
These references were created for different purposes. Label the selected model instead of mixing durations from one system with thresholds from another.
Mixed Exposure
Dose fraction = C1/T1 + C2/T2 + ... + Cn/TnC is the actual duration at a level and T is the permitted duration under the selected model. Tuning runs, demonstrations, road use, work noise, headphones, and other events all contribute to the period being evaluated.
Competition Score Is A Different Measurement
A narrowband cabin-pressure score may use a pressure sensor, a special placement, a short hold, and little or no hearing-risk weighting. It is useful for the competition question. It does not replace an ear-position exposure measurement, true-peak record, or total dose log.