Audiometric Testing: Baseline, Annual Tests, and STS
Audiometric testing is the part of a hearing conservation program that runs forever. It’s the only component that actually measures whether the program is working.
Audiometric testing is the part of a hearing conservation program that runs forever. The written program is a one-time document. Training cycles annually. Testing also cycles annually, and it’s the only component that actually measures whether the program is working: each test compares an employee’s current hearing against their own baseline, and a meaningful change triggers specific obligations on the employer.
This piece walks through how baseline and annual tests work in a California program, what counts as a standard threshold shift (STS), and what has to happen when one is identified.
What Audiometric Testing Is
An audiometric test (an audiogram) measures the quietest sound an employee can hear at standard frequencies in each ear, in a sound-isolated booth, using a calibrated audiometer. Under Title 8, Section 5097 of the California Code of Regulations, this isn’t a diagnostic medical exam. It’s a compliance tool: the employer needs to know whether continued noise exposure is causing measurable hearing loss in enrolled employees. The test has to be administered by a licensed or certified audiologist, an otolaryngologist (ear, nose, and throat physician), or another physician. It can also be administered by a technician certified by the Council for Accreditation in Occupational Hearing Conservation (CAOHC), or one who has demonstrated competence, under the supervision of a qualified physician or audiologist.
The Baseline Audiogram
The baseline is the reference point every future test for that employee is compared against. Get it wrong, and the rest of the program’s measurement framework is compromised.
Three rules drive the baseline in California:
Timing
The baseline must generally be obtained within 6 months of an employee’s first exposure at or above the 85 dBA action level. If a mobile test van is used, Cal/OSHA allows testing within one year, provided employees have an opportunity for testing; if the baseline is not obtained within 6 months under that approach, hearing protectors must be provided and worn until the baseline is obtained.
The 14-hour quiet rule
The baseline has to be preceded by at least 14 hours without exposure to workplace noise. The cleaner approach is to schedule the test for the start of a shift after a day off or a weekend. The point is to capture the employee’s true baseline hearing, not a temporary threshold shift from yesterday’s exposure.
Documentation
The audiogram, the date, the technician, the audiometer calibration record, and the background noise levels in the test booth all become part of the employee’s record, retained for the duration of employment under §5100.
The 14-hour quiet rule catches more programs out of compliance than any other detail. When we audit existing programs, baselines on file were often scheduled mid-shift or right after the employee came off the production floor. Those baselines are technically defective. They can be replaced, but it means an extra round of testing and a delay in establishing the employee’s true reference point.
The Annual Audiogram
After the baseline, each enrolled employee receives an annual audiogram, performed within one year of the baseline and every year after that. The procedure is identical to the baseline. What changes is what happens with the result: every annual audiogram is compared against the baseline to look for a standard threshold shift.
The most common gap we find when auditing existing programs is missing annual audiograms. PPE on the floor is still in use, training records are usually in some form, but the audiometric cycle has stopped. Sometimes the testing provider changed and the schedule never restarted. Sometimes the program administrator left and the calendar went with them. Either way, the employer is out of compliance, and the program no longer has the data to detect hearing loss in time to act on it.
Standard Threshold Shifts
A standard threshold shift (STS) converts the audiometric testing program from a passive measurement into active employer obligations. Under §5097, an STS is a change in hearing threshold relative to the baseline of an average of 10 dB or more at 2000, 3000, and 4000 Hz in either ear.
The average matters. A 15 dB shift at one frequency, by itself, isn’t an STS. But a 10 dB shift averaged across the three relevant frequencies is, and once that line is crossed, the regulation triggers a specific sequence of employer actions.
Age correction (presbycusis correction) is permitted. The decision to apply it is the employer’s, in consultation with the reviewing audiologist or physician. We typically recommend applying age correction only when the unadjusted comparison shows an STS, not as a routine first pass.
The Audiometric Testing Timeline
The full cycle for a single enrolled employee:
- 1Enrollment.
- 2Baseline audiogram generally within 6 months
- 3Annual audiogram within one year of the baseline.
- 4STS comparison.
- 5If an STS is identified:The employee must be informed in writing within 21 days of the determination.
- 6Refit and retrain.
- 7Follow-up testing or referral.
- 8Recordable case decision.
- 9Repeat annually.
Enrollment.
Employee’s TWA exposure measured at or above 85 dBA. They are added to the program.
Baseline audiogram generally within 6 months
(up to 1 year with mobile test van). Preceded by at least 14 quiet hours.
Annual audiogram within one year of the baseline.
Same procedure as the baseline.
STS comparison.
Annual result compared against the baseline. Age correction applied at employer discretion if it changes the outcome.
If an STS is identified:
The employee must be informed in writing within 21 days of the determination.
Refit and retrain.
Employees not already using hearing protectors must be fitted, trained, and required to wear them. Employees already using protectors must be refitted, retrained, and provided protectors with greater attenuation if necessary.
Follow-up testing or referral.
Where appropriate, a retest is performed; if a medical pathology is suspected, the employee is referred for clinical audiological or otological evaluation.
Recordable case decision.
If the STS is work-related and the employee’s total hearing level meets the recording threshold under Title 8 §14300.10 (25 dB or more above audiometric zero, averaged at 2000, 3000, and 4000 Hz, in the same ear(s) as the STS), the case must be recorded on the Cal/OSHA Form 300.
Repeat annually.
The cycle continues for as long as the employee remains in the program.
For a facility with 30 enrolled employees, that’s 30 annual audiograms, 30 STS comparisons, and a handful of STS follow-ups in any given year. None of it is optional once the program is in place.
What Happens When an STS Is Found
The 21-day written notification is the first hard deadline. We see facilities miss it because the audiogram came back to the safety manager, sat in an inbox, and the calendar slipped. Once that window closes without action, the employer is in a documented compliance gap an inspector can identify quickly.
After notification, the refit and retrain step is where the program actually does its job. A work-related or potentially work-related STS requires the employer to review hearing protection and follow the §5097(d) response steps. It does not automatically prove that the existing protector was inadequate (the STS may be non-work-related or non-persistent after retest), but it does require refitting, retraining, and providing protectors with greater attenuation if necessary. The response options are: better-attenuating protectors, a different style that fits the employee correctly, or dual protection for high-exposure tasks. If the STS is work-related and the employee’s total hearing level also meets the Cal/OSHA recording threshold in Title 8 §14300.10, the case must be recorded on the Cal/OSHA Form 300. The recordability decision is separate from the STS finding: a shift can be an STS for §5097 purposes without being recordable, depending on the employee’s overall hearing level.
Recordkeeping for Audiometric Tests
In California, audiometric test records have to be retained for the duration of the affected employee’s employment. That’s longer than the 2-year retention for noise exposure measurements under the same standard. Records include the employee’s name and job classification, the audiogram date, the examiner’s name, the date of audiometer calibration, the employee’s most recent noise exposure assessment, and the background sound pressure levels in the test booth. Programs that store audiometric records in one administrator’s inbox are programs that lose them.
The Recurring Burden, Honestly
Audiometric testing is the largest ongoing cost in a hearing conservation program after it’s in place. This is why we raise engineering controls every time the noise profile is borderline. Reducing exposure at the source below 85 dBA can remove an enrolled job role from the program entirely, and the recurring testing obligation with it. That’s not a sales pitch against the program. The program is required when exposure crosses the action level, and we develop and administer it. It’s a budgeting reality worth understanding before the recurring obligation starts. For the comparison of controls, see engineering and administrative controls for workplace noise. For how training fits the same annual cycle, see hearing conservation training requirements.
Trusted throughout California
BSY started working with CDMS last year after our in-house EHS person departed the company. CDMS reviewed our existing operational permits as well as any additional Federal, State and Local regulations that could apply and helped us to create a comprehensive compliance calendar to track regulatory deadlines and submittal due dates. The CDMS team does an excellent job of tracking everything and can be relied upon to complete the forms accurately and assist with submittals, allowing me to focus on our business.
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