Noise Dose Calculator: NIOSH and OSHA Exposure on iPhone

Q: Is the noise exposure calculator free?

Yes. The whole Exposure tab, including saved sessions and their CSV export, is free with no ad to watch. Only the Daily Noise Dose screen in Stats needs Premium or a rewarded ad.

Q: Can I use it as an OSHA noise exposure calculator?

Yes: pick OSHA PEL under Standard and the app uses the 90 dBA criterion and 5 dB exchange rate. The result is for your own information, not a record for an inspection.

How do you calculate noise dose percentage?

Every level has an allowed time per day. That's the whole idea. For each part of the day, divide the time you spent by the time allowed at that level, then add the fractions: D = 100 × Σ (time ÷ allowed time).

The allowed time halves each time the level rises by the exchange rate: T = 8 h ÷ 2^((L - criterion) ÷ exchange rate). Below 80 dBA nothing counts towards the dose.

The two standards the app offers
	NIOSH REL	OSHA PEL
Criterion (100% in 8 hours)	85 dBA	90 dBA
Exchange rate	3 dB	5 dB
Threshold (no dose below it)	80 dBA	80 dBA
What it is	Health-based recommendation	US workplace permissible limit

What is the permissible noise exposure time at each level?

NIOSH and OSHA noise exposure table from the app's formula (rounded down to the minute, or to the second under 5 minutes)
Level (dBA)	NIOSH REL	OSHA PEL
85	8 h	16 h
88	4 h	10 h 33 min
90	2 h 31 min	8 h
91	2 h	6 h 57 min
94	1 h	4 h 35 min
95	47 min	4 h
97	30 min	3 h 1 min
100	15 min	2 h
105	4 min 43 s	1 h
110	1 min 29 s	30 min

How to measure your noise dose in the app

Open the Exposure tab.
Under Standard, choose NIOSH REL or OSHA PEL. Switching standard restarts the running measurement.
Optional but worth it: tap the Calibration row and enter your offset against a reference meter.
Tap Start Exposure Measurement when the shift, rehearsal or workshop session begins. Keep the phone on you or near you and uncovered, not deep in a bag.
Follow SPL now, LAeq, the Dose ring and Time left at current level. The measurement keeps running in the background.
Tap Stop & Save Session. The result is kept in Sessions (list button), where Export this session as CSV or Export CSV exports one session or all of them.

What do dose, projected dose and TWA mean?

Dose: the share used so far. Below 50% the ring says Within daily limit, from 50% Half the daily limit passed, and from 100% Daily limit exceeded.
Projected 8 h dose: where you would end after 8 hours if the rest of the day is like the part measured. One hour at a steady 88 dBA under NIOSH is a 25.0% dose and a projected 200%.
TWA (8 h): the steady level for 8 hours that would give the same dose, TWA = criterion + exchange rate × log2(dose ÷ 100).
Time left at current level: how long until 100% if the level stays where it is. With 50% used and 91 dBA under NIOSH, it shows 1h 0m; below 80 dBA it shows ∞.

Worked example: a 3.5-hour noisy shift

Take a noisy shift of 2 hours at 85 dBA, 1 hour at 91 dBA and 30 minutes at 94 dBA, with the rest of the day quiet.

Dose per part of the day (shares rounded; the app adds the exact values)
Part of the day	NIOSH share	OSHA share
2 h at 85 dBA	25.0%	12.5%
1 h at 91 dBA	50.0%	14.4%
30 min at 94 dBA	50.0%	10.9%
Dose	125.0%	37.7%
TWA (8 h)	86.0 dBA	83.0 dBA

Same day, two verdicts: over the NIOSH recommendation, well inside the OSHA limit. The gap comes from the 3 dB versus 5 dB exchange rate, and it is why NIOSH is the cautious choice for your own hearing.

Daily Noise Dose from saved recordings

The Stats tab has a second, simpler tool: Daily Noise Dose (NIOSH exposure calculator). It adds up today's saved Meter recordings using each one's average and duration, always with NIOSH. It needs Premium or a rewarded ad for 24 hours; the Exposure tab does not.

Example: a 45-minute recording averaging 88 dB and a 20-minute one averaging 95 dB give a dose of 61%, a TWA of 82.8 and 3h 8m of Safe Exposure Remaining at 85 dBA.

Questions and answers

What does a 100% noise dose mean?

You have used the whole daily allowance of the chosen standard: the same as 8 hours at 85 dBA under NIOSH, or 8 hours at 90 dBA under OSHA. Anything above 100% is more than the standard allows for one day.

Is the noise exposure calculator free?

Yes. The whole Exposure tab, including saved sessions and their CSV export, is free with no ad to watch. Only the Daily Noise Dose screen in Stats needs Premium or a rewarded ad.

Can I use it as an OSHA noise exposure calculator?

Yes: pick OSHA PEL under Standard and the app uses the 90 dBA criterion and 5 dB exchange rate. The result is for your own information, not a record for an inspection.

How is this different from a real noise dosimeter?

A dosimeter is a calibrated instrument worn near the ear for the whole shift. The app uses the same formulas, but its input is a phone microphone that you place yourself, so treat the dose as an estimate.

How many decibels is too loud? A decibel levels chart with real examples · Decibel Sound Meter
What is LAeq in noise measurement? The average noise level, with real numbers · Decibel Sound Meter

Noise dose calculator: your NIOSH and OSHA daily exposure, on your phone