Your Daily Total
Exposure limits are written per day, and the day includes everything. Most people account for one part of it.
When employers review noise dose alongside working patterns, employee time clock software can provide operational context, while exposure limits still need to be assessed from sound level and duration.
Why the total is the unit
The cochlea does not know which activity produced the sound.
An eight-hour shift at 82 dBA uses a substantial part of the daily allowance, and what happens afterwards adds to it rather than starting fresh.
For an independent reference on this subject, see NIOSH noise and hearing-loss guidance.
The limits are daily totals, and a workplace assessment showing compliance describes the workplace rather than the person.
How to add exposures
Not by adding decibels. Decibels do not add arithmetically.
By adding fractions of the allowance.
Each exposure uses a fraction: time spent ÷ time permitted at that level. Permitted time comes from the exchange rate.
Add the fractions. If the total exceeds 1, the daily limit is exceeded.
Worked: six hours at 85 dBA is 6 ÷ 8 = 0.75. Thirty minutes at 94 dBA is 0.5 ÷ 1 = 0.5. Total 1.25 — over the limit, from a shift most people would call moderate plus half an hour.
Where the total usually comes from
One activity, not the sum of many.
Because of the exchange rate, a short intense exposure frequently dominates: an hour at 94 dBA is a full day's allowance on its own.
Commuting on a motorcycle or by underground rail. A power tool for twenty minutes. A gym class. A bar. Headphones at volume for a long journey.
The eight-hour job at 78 dBA contributes almost nothing while feeling like the main event, and that inversion is the practical finding.
What to do with the arithmetic
Run it once for a typical day. Ten minutes with a rough level for each activity.
Find the dominant term, which is usually a surprise and is usually short.
Address that one. Reducing a dominant exposure by 3 dB halves the whole day's dose; reducing three minor ones changes nothing measurable.
The limits of doing this yourself
Estimated levels carry error, and a phone measurement carries more than people assume.
A dosimeter worn for a shift is the proper instrument for occupational exposure and answers the question directly.
But the arithmetic is worth doing even with rough numbers, because it reliably identifies which activity matters, and that conclusion survives a fair amount of error in the inputs.
The short version
- Limits are daily totals, and a compliant workplace assessment describes the workplace rather than the person
- Add exposures as fractions of the allowance — time spent divided by time permitted at that level — and a total above 1 exceeds the limit
- Six hours at 85 dBA plus thirty minutes at 94 dBA is 1.25 of a day
- Because of the exchange rate, one short intense exposure usually dominates the total
- The eight-hour job at 78 dBA contributes almost nothing while feeling like the main event
- Run it once with rough numbers: the identification of the dominant activity survives considerable error in the inputs