Audiometer Calibration: Daily Biological Check and Acoustic Calibration Requirements

OSHA requires audiometer calibration under 1910.95. This guide covers daily biological check requirements, annual acoustic calibration, exhaustive calibration triggers, documentation requirements, and what happens to audiograms from uncalibrated equipment. According to CDC/NIOSH, approximately 22 million U.S. workers are exposed to hazardous occupational noise annually. OSHA 29 CFR 1910.95 governs the audiometric testing and recordkeeping that underlies all of these clinical topics.

Soundtrace audiometric testing is supervised by a licensed audiologist who reviews every audiogram — catching clinical findings that automated algorithms alone may miss and ensuring every compliance and clinical obligation is met.

Three Levels of Audiometer Calibration Under OSHA 1910.95

OSHA 1910.95 Appendix E establishes three calibration levels for audiometers: (1) daily functional check (biological check); (2) acoustic calibration at least annually; and (3) exhaustive calibration when the annual acoustic check reveals performance outside acceptable limits.

Daily Biological Check

Before each day of use, the audiometer must be checked using a person with known stable hearing thresholds. The purpose: confirm the audiometer is producing tones at approximately the correct levels and that no major malfunction has occurred since the last use. The biological check person listens to each tone at a standard level and confirms they can hear it. If results deviate significantly from the checker's stable thresholds, the audiometer should not be used until the problem is investigated.

Documentation: the date, checker's identity, and results of the biological check must be recorded. Test results from audiometers without documented daily biological checks may be challenged as invalid during OSHA inspections.

Annual Acoustic Calibration

At least annually, the audiometer must have its output levels acoustically calibrated using a calibrated sound level meter with a coupler designed for the audiometer's earphone type. The calibration verifies that the audiometer is producing tones at the correct sound pressure levels at each frequency and each level setting. Annual acoustic calibration must be performed by a qualified technician and results documented.

For automated audiometric testing systems that perform self-calibration, the system's calibration records must document that calibration occurred and met acceptable tolerances before each audiometric session.

Exhaustive Calibration

If the annual acoustic calibration reveals that the audiometer's output is outside acceptable limits at any frequency or level, an exhaustive calibration is required before further use. Exhaustive calibration is a comprehensive technical service that goes beyond the annual acoustic check. Audiograms conducted between the last valid acoustic calibration and the discovery of the calibration failure may need to be repeated if the calibration error was large enough to affect test results.

What Happens to Audiograms from Uncalibrated Equipment

Audiograms conducted with uncalibrated equipment are not valid for OSHA compliance purposes and are not defensible in WC proceedings. If an audit reveals that an employer's audiometer was not acoustically calibrated on the required annual schedule, the audiometric records from the non-calibrated period are of uncertain validity. This is one of the most common technical deficiencies found during OSHA inspections of audiometric programs.