Audiometer Calibration Vendor Selection: Questions to Ask First

What does OSHA actually require from a calibration vendor?

OSHA's hearing conservation standard doesn't license or approve calibration vendors; it sets requirements for the calibration itself. Under 29 CFR 1910.95, an audiometer needs an acoustic calibration checked at least annually against the tolerances in Appendix E, and an exhaustive calibration at least every two years performed to the listed sections of ANSI S3.6-1969, or a later edition OSHA has treated as equally protective. The employer is on the hook either way; the regulation doesn't care whether the work was done in-house or by a vendor, only that the record shows the right interval, the right tolerances, and a result the employer can produce on demand. That means vendor selection is really about finding someone who will hand you a record that holds up, not about finding someone with a certification OSHA requires, because no such vendor certification exists.

What should the calibration certificate actually list?

A certificate that just says "passed" doesn't meet the bar most auditors expect, and it doesn't give you anything to compare against next year's result. A usable certificate lists the measured sound pressure output at each test frequency for each earphone, the deviation from the reference tables, the date of the check, the standard and edition used (S3.6-1969, 2004, or 2018), and the reference standard's own traceability. If a vendor can't produce measured values, only a pass/fail stamp, you have no way to see a 10 dB drift developing before it crosses OSHA's threshold and forces an unscheduled exhaustive calibration.

Need the annual acoustic check or the two-year exhaustive calibration done? Foster's audiometer calibration service returns measured values at every frequency, not just a pass/fail result, so the certificate holds up against audit and shows drift before it becomes a failure.

What does "NIST traceable" actually mean here?

OSHA's standard doesn't use the phrase "NIST traceable," but it does require the calibrating equipment to be accurate enough to confirm the audiometer meets S3.6 tolerances, which in practice means the vendor's own reference equipment, the sound level meter, octave-band filter set, and coupler used to run your check, has its own documented calibration chain back to a national standard. Ask a vendor for the calibration certificate on their reference equipment, not just yours. A vendor who can't produce that is asking you to trust a number with no verified basis behind it.

Which ANSI S3.6 edition does the vendor test to, and does it matter?

1910.95 still names ANSI S3.6-1969 directly, but OSHA has issued standard interpretation letters treating the 2004 and 2018 revisions as equally protective, meaning a vendor testing to a newer edition isn't creating a compliance gap. CAOHC's OHC responsibilities guidance likewise ties the annual calibration check to keeping the required logs and forms current, not to any single standard edition. What matters is that the vendor states which edition they used on the certificate and that the result is internally consistent: an audiometer checked to 2018 tolerances one year and 1969 tolerances the next makes year-over-year comparison harder, even though either edition alone is acceptable. Ask the vendor which edition they standardize on and whether they'll stay consistent across your fleet and across years.

How fast can the vendor turn an exhaustive calibration around?

An exhaustive calibration takes the instrument out of service, typically by mail-in, for the vendor to run the full S3.6 procedure. A facility with one audiometer and testing scheduled on a fixed calendar needs to know the real turnaround, not the vendor's best case, before relying on that calendar. Ask for the typical turnaround in writing, what happens if the unit fails and needs repair mid-calibration, and whether a loaner is available. A facility running testing year-round with no backup instrument is exposed every time its only audiometer is in transit.

Question	Why it matters
Does the certificate list measured values per frequency, or just pass/fail?	Measured values let you track drift and defend the record under audit
What's the traceability chain on your own reference equipment?	The vendor's check is only as good as what their equipment is calibrated against
Which ANSI S3.6 edition do you test to, and is it consistent year to year?	Any accepted edition is fine; inconsistency makes trend comparison harder
What's the real turnaround for an exhaustive calibration, and is a loaner available?	Determines how much testing downtime to plan for
Do you calibrate on-site or mail-in only?	On-site avoids downtime but may not be offered for every instrument model

How Foster handles vendor-grade calibration

Foster's audiometer calibration service is NIST-traceable, available mail-in or on-site, and every certificate lists the measured sound pressure output at each frequency against the reference tables, not a bare pass or fail. We test to a consistent ANSI S3.6 edition across a customer's fleet so year-over-year drift is actually comparable, and we flag any unit approaching the 10 dB functional-check or 15 dB exhaustive-calibration deviation threshold before it fails outright. For employers weighing whether to build an in-house calibration capability instead, see our related post on in-house vs. vendor calibration cost and risk.

Frequently asked questions

Is a NIST-traceable certificate legally required for OSHA compliance?

OSHA's standard doesn't use the phrase "NIST traceable," but it requires the calibrating equipment to be accurate enough to confirm the audiometer meets ANSI S3.6 tolerances. A documented traceability chain is the practical way a vendor proves that accuracy, and it's what most auditors expect to see even though the regulation doesn't spell out the term.

Does it matter if a vendor uses ANSI S3.6-2018 instead of the 1969 edition named in 1910.95?

No. OSHA has issued standard interpretation letters treating the 2004 and 2018 revisions of ANSI S3.6 as equally protective of workers as the 1969 edition the regulation names, so a vendor testing to a current edition isn't out of compliance.

What deviation triggers an exhaustive calibration instead of just the annual acoustic check?

Under Appendix E, a deviation of 15 dB or more at any test frequency on the annual acoustic check requires an exhaustive calibration rather than waiting for the normal two-year interval. A good vendor certificate shows the measured deviation at each frequency so you can see this coming.

Should every audiometer in a fleet use the same calibration vendor?

Not strictly required, but it makes the record easier to defend. Using one vendor, or at least one consistent ANSI S3.6 edition and reporting format across all units, keeps drift comparisons and audit review straightforward instead of reconciling different certificate formats from multiple sources.

For calibration scheduling or a quote across a multi-unit fleet, see Foster's calibration services or request a quote.

Sources

• 29 CFR 1910.95, occupational noise exposure and audiometer calibration requirements
• CAOHC, OHC responsibilities for audiometer calibration and recordkeeping