Baseline vs Monitoring Audiograms Explained
Audiogram testing in the workplace serves two distinct purposes, and many employers treat both types of hearing tests as interchangeable. Understanding the difference between a baseline audiogram and a monitoring audiogram matters for compliance, for employee safety, and for long-term hearing conservation.
What Is a Baseline Audiogram
A baseline audiogram is the first hearing test an employee receives after being enrolled in a hearing conservation program. It measures hearing thresholds at specific frequencies in each ear and creates a permanent reference point. Every future hearing evaluation is compared against this initial test.
Our friends at Health Care Centers of Florida perform baseline audiograms as part of comprehensive occupational screening services, and the process is straightforward. The employee sits in a controlled testing environment, listens for tones at varying pitches and volumes, and responds when a sound is detected. The entire test typically takes less than thirty minutes.
OSHA’s occupational noise exposure standard (29 CFR 1910.95) requires employers to obtain a valid baseline audiogram within six months of an employee’s first exposure at or above the 85 dBA action level. The employee must have at least 14 hours without workplace noise exposure before the test is administered. This quiet period is not optional. It prevents temporary hearing fatigue from distorting the results.
What Is a Monitoring Audiogram
A monitoring audiogram, often called an annual audiogram, is a follow-up hearing test performed at regular intervals after the baseline has been established. Its purpose is detection. Specifically, the monitoring audiogram identifies whether an employee’s hearing has changed over time due to workplace noise exposure.
Each annual test is compared directly against the baseline. If the average hearing threshold at 2,000, 3,000, and 4,000 Hz worsens by 10 dB or more in either ear, OSHA defines that as a Standard Threshold Shift, or STS. That shift triggers a series of required actions from the employer, including:
- Notifying the affected employee in writing within 21 days
- Refitting or replacing hearing protection devices
- Providing additional training on hearing conservation
- Referring the employee for further audiological evaluation if needed
- Evaluating whether the shift should be recorded on the OSHA 300 Log
Without a valid baseline on file, none of these comparisons are possible. The monitoring audiogram has no reference point, which means it has no compliance value beyond satisfying a scheduling requirement.
How to Stay Ahead of Hearing Conservation Requirements
The most effective approach is to build audiogram testing into your onboarding process and maintain a consistent annual testing schedule for all noise-exposed employees. Keep records organized. Audiometric records must be retained for the duration of each employee’s employment, and noise exposure measurement records must be kept for at least two years. If your company needs to schedule baseline or monitoring audiograms, or if you have questions about your hearing conservation program, reach out to a physician to set up an appointment.