Baseline Audiogram Rules: Deadlines and Exceptions Explained

When must a baseline audiogram be completed?

29 CFR 1910.95 requires a baseline audiogram within 6 months of an employee's first exposure at or above the 85 dBA action level (an 8-hour time-weighted average). The baseline is the reference point every future annual audiogram gets compared against to detect a standard threshold shift, so a late or missing baseline doesn't just violate the deadline — it leaves the entire program with no valid comparison point for that employee until one is established. Employers should treat the 6-month window as a hard scheduling deadline tied to each employee's hire or first-exposure date, not a general annual testing cycle.

Why does OSHA require a 14-hour quiet period before baseline testing?

Recent noise exposure temporarily raises a person's hearing threshold — a phenomenon called temporary threshold shift — which can make a baseline look worse than the employee's true unexposed hearing. To get a clean reference point, employees should be away from workplace noise for at least 14 hours before a baseline test, either by scheduling the test before a noisy shift starts or by having the employee wear hearing protectors for that period as a substitute for the quiet-time requirement. A baseline taken right after a loud shift, with no quiet period and no protection, risks recording an artificially depressed threshold that then makes every future annual test look like an improvement rather than an accurate trend.

What is the mobile test van exception?

Employers using a mobile test van to reach multiple sites get more scheduling flexibility: the baseline deadline extends to 1 year from an employee's first exposure instead of 6 months. In exchange for that extra time, employees must wear hearing protectors from the sixth month until the baseline is actually completed, so the tradeoff isn't a free pass — it shifts the compliance burden from "get the test done fast" to "protect the employee's hearing until the test happens." This exception exists specifically for employers whose testing logistics depend on a van's travel schedule, not as a general extension available to any program.

Testing method	Baseline deadline	Condition
Standard (fixed-location testing)	6 months from first exposure	14-hour quiet period or hearing protection before test
Mobile test van	1 year from first exposure	Hearing protectors required from month 6 until baseline

What happens if an employee misses the 6-month deadline?

A missed baseline deadline is a recordkeeping violation that also compromises the program going forward — without a valid baseline, there's no clean reference for calculating whether a later audiogram shows a standard threshold shift. The corrective action is to test the employee as soon as the miss is discovered, document why the deadline was missed, and treat the eventual test as the baseline going forward while flagging in the record that it fell outside the required window. The better fix is preventing the miss: tracking first-exposure dates for every new hire and scheduling baseline testing before the 6-month clock runs out, which is one of the more common gaps found during a hearing conservation program self-audit.

How does Foster track baseline deadlines for a new hire?

When a new employee enters a hearing conservation program, Foster logs their first-exposure date at intake and flags the 6-month (or 1-year, for mobile-van programs) deadline against the employer's testing calendar rather than leaving it to whichever visit happens to fall next. If a new hire's start date means the next scheduled site visit would land after their deadline, the technician calls that out to the employer ahead of time so an interim test can be arranged instead of quietly missing the window. On testing day, the tech confirms with each new employee when their last noise exposure was, to catch anyone who came in straight from a loud shift and needs rescheduling to preserve the 14-hour quiet period rather than recording a compromised baseline.

What does an auditor ask about baseline timing?

An inspector reviewing a hearing conservation program typically pulls a sample of employee files and checks two dates against each other: the date of first noise exposure (often the hire date, unless the role changed later) and the date of the baseline audiogram. A gap over 6 months with no mobile-van justification on file is an immediate finding. The second thing an inspector checks is whether the record shows evidence of the 14-hour quiet period or hearing protector use before the baseline test — a program that can't show either leaves every subsequent threshold-shift calculation open to challenge, since there's no way to confirm the reference point itself was clean.

Frequently Asked Questions

Can an employee's pre-employment hearing test count as the baseline?

Only if it meets the same requirements as a workplace baseline — proper equipment, calibration, and quiet-period conditions — and was completed within the required window relative to first occupational noise exposure.

Does the 14-hour quiet period mean the employee can't wear hearing protection during that time?

No — hearing protectors worn during that 14-hour period are an accepted substitute for actual quiet, since the goal is preventing noise-induced temporary threshold shift, not requiring literal silence.

What if an employee refuses a baseline audiogram?

Employers should document the refusal and the outreach made to schedule the test; a refusal doesn't remove the employer's obligation to attempt compliance, and repeated refusals should be addressed through the employer's own workplace policy.

Foster Special Instruments delivers on-site hearing testing and hearing conservation program management built around these deadlines. See the full OSHA hearing conservation checklist for the rest of the program.