A full shift of noise dosimetry is only as good as the two minutes spent on noise dosimeter calibration before the device goes on the worker. If the microphone drifted, the battery sagged or the unit took a knock on the haul road, the dose report looks perfectly normal and is still wrong. For a safety manager building a hearing conservation record, or a lab that has to defend every certificate it issues, calibration is what separates a measurement from a number.
What OSHA and MSHA expect from noise dosimeter calibration
OSHA’s noise standard leaves the details to the manufacturer. Appendix G of 29 CFR 1910.95 says the calibration and maintenance instructions in the dosimeter and sound level meter manuals should be followed, and describes calibrating instruments before and after each use as good professional practice.
MSHA’s noise survey guidance for mines follows the same pattern. The dosimeter is field calibrated before and after the survey, the sound level meter used for area readings gets the same treatment, and both the dosimeter and the field calibrator must have a current annual calibration on record.
In practice, that creates two separate jobs: a quick check in the field every time the instrument is used, and a periodic calibration of both the instrument and the calibrator itself.
Field check vs. lab calibration: two different jobs
The field check uses an acoustic calibrator, a small sound source that fits over the microphone and produces a known level, typically 94 dB or 114 dB. The technician reads the dosimeter against that reference before the shift, adjusts if needed, and repeats the check at the end. If the end-of-shift reading has moved beyond the program’s tolerance, the data from that run is questionable. The check takes minutes and catches the everyday problems: a damaged microphone, a loose windscreen, a low battery.
Lab calibration is a different service. The instrument goes to a calibration laboratory, is tested across levels and frequencies against reference equipment, and comes back with a certificate. The acoustic calibrator needs the same treatment, because a field check is only as reliable as the reference it uses. A calibrator that has drifted will pass a dosimeter that is wrong.
That is why mining operations and labs plan calibration as a recurring cycle, with the dosimeter and the calibrator on the same calendar.
Building a calibration routine that holds up
A defensible routine starts with the manufacturer’s manual, as OSHA points out, and adds a few habits. Check every noise dosimeter before and after each measurement and record both readings with the results. Log the serial number of the calibrator used, so every dose report can be traced back to a reference. Keep annual certificates for the dosimeters and the calibrator in the same file. If you are still deciding which instrument fits each task, see our guide on noise dosimeters vs. sound level meters.
For the field check, Svantek’s acoustic calibrators cover the common cases. The SV 33B is a Class 1 calibrator under IEC 60942:2017 that produces 114 dB with a tolerance of ±0.25 dB. The SV 36 is also Class 1 and lets the user choose between 94 dB and 114 dB, and an infrared sensor switches it on when a microphone is inserted. The SV 34B is the Class 2 option, at 114 dB with ±0.4 dB. According to Svantek, all three measure temperature and static pressure with built-in sensors and correct the output automatically, which matters when the check happens underground, outdoors or at altitude. They accept 1/2″ microphones directly and 1/4″ microphones with the SA 30 adapter.
Conclusion
Noise dosimeter calibration is a short task with long consequences. A field check before and after every measurement, a calibrator with a current certificate and a clear record of both turn a dose report into evidence a mine, a lab or an auditor can rely on.
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