A workplace noise exposure assessment determines which employees are exposed to hazardous noise levels, quantifies their exposure for comparison to OSHA's action level and PEL, and provides the documentation foundation for your hearing conservation program. Here is how to conduct one that satisfies OSHA requirements and produces defensible data.
Soundtrace replaces periodic noise monitoring campaigns with continuous workplace noise exposure data — giving you always-current TWA readings for every job classification without scheduling a monitoring visit every time something changes.
When Noise Monitoring Is Required by OSHA
Under 29 CFR 1910.95(d), general industry employers must monitor employee noise exposures when information indicates that any employee's noise exposure may equal or exceed 85 dBA as an 8-hour TWA — the action level. The monitoring requirement is triggered by a reasonable belief that exposures may be at or above the action level, not by confirmed measurement above it.
| Threshold | Level | Consequence |
|---|---|---|
| Action Level (AL) | 85 dBA TWA | Full hearing conservation program required; all 6 elements |
| Permissible Exposure Limit (PEL) | 90 dBA TWA | Feasible engineering/admin controls required; HPDs mandatory |
| Impulsive Noise Peak | 140 dBC peak | Absolute limit; no safe duration |
Instruments: Dosimetry vs. Area Monitoring
Personal noise dosimeters clip to the worker's collar and record cumulative noise dose throughout the shift. They automatically calculate the 8-hour TWA. Dosimetry is required when workers move between noise environments or when noise levels vary significantly during the shift. It is the preferred OSHA compliance method for mobile workers.
Integrating sound level meters (Type 2 minimum per ANSI S1.4) measure noise levels at fixed locations. Appropriate for characterizing area noise levels, evaluating engineering controls, and initial screening. Area measurements alone are insufficient for compliance assessment of workers who move through multiple noise environments.
Instrument Settings for OSHA Compliance
| Setting | OSHA Value | Why |
|---|---|---|
| Frequency weighting | A-weighting (dBA) | Correlates with hearing damage risk |
| Criterion level | 90 dBA | OSHA PEL; dosimeter uses this as 100% dose reference |
| Threshold level | 80 dBA | Captures all noise contributing to action-level dose |
| Exchange rate | 5 dB | OSHA doubling rate; NIOSH uses 3 dB |
| Time response | Slow | OSHA standard for steady/continuous noise |
Conducting the Assessment
Step 1 — Preliminary walkthrough: Use a basic SLM to identify areas and tasks that warrant formal dosimetry. Flag any work area where conversation requires raised voice (approximately 85 dBA ambient).
Step 2 — Select workers for monitoring: Monitor representative workers in each job classification with potential action-level exposure. If monitoring all workers is impractical, use Similar Exposure Groups (SEGs) — groups with similar job tasks, locations, and equipment.
Step 3 — Dosimeter setup: Configure dosimeter to OSHA settings (see table above). Mount the microphone on the worker's collar near the ear, away from the shoulder. Verify calibration before and after each session.
Step 4 — Conduct full-shift monitoring: OSHA requires monitoring of the full work period to capture representative exposure. Do not start monitoring mid-shift for tasks with varying noise levels. Document any atypical conditions (equipment outages, production slowdowns).
Step 5 — Post-measurement calibration: Verify calibration after completing measurements. A drift of more than 1 dB from the pre-measurement check renders the session's data questionable.
Analyzing Results: TWA, Dose, and Enrollment Decisions
The dosimeter automatically calculates the 8-hour TWA and noise dose percentage. To interpret results against OSHA thresholds:
- TWA ≥ 85 dBA (dose ≥ 50%): Employee meets action level criteria; enroll in hearing conservation program
- TWA ≥ 90 dBA (dose ≥ 100%): Employee at or above PEL; feasible engineering/administrative controls required; hearing protection mandatory
- TWA < 85 dBA (dose < 50%): Below action level; no HCP enrollment required; document result and schedule re-monitoring per your triggers
For area measurements used to assess fixed-location workers: compare the measured area level to OSHA's permissible duration table, accounting for time spent in the area. Workers spending only part of the shift in a measured area require a composite dose calculation.
When to Re-Monitor
OSHA requires re-monitoring whenever a change in production, process, equipment, or controls may increase employee exposures to the action level. Specific re-monitoring triggers include: new equipment installation, production rate increases, changes in materials or processes, implementation of engineering controls (to verify the achieved noise reduction), layout changes that affect worker-to-source distance, and STS findings in workers not previously identified as overexposed.
Documentation Requirements
OSHA requires noise exposure monitoring records to be retained for at least 2 years. Records must include: date of monitoring, area or task monitored, instrument type and calibration date, instrument settings, individual employee names and results, and noise exposure determinations. Best practice includes: SEG definitions and sampling rationale, pre- and post-measurement calibration check results, and re-monitoring schedule. See: OSHA Recordkeeping Compliance Documentation.
Frequently Asked Questions
OSHA does not specify a fixed interval for re-monitoring. Monitoring must be repeated whenever changes in production, process, equipment, or controls may increase exposures to the action level. Many employers establish a baseline survey with periodic re-monitoring (every 2-3 years) plus event-triggered re-monitoring per OSHA's re-monitoring requirement.
Yes. Under 29 CFR 1910.95(e), employees and their representatives must be given the opportunity to observe noise monitoring. This is a compliance requirement, not just best practice. Employees must also be notified of the results of monitoring in which they participate.
No. OSHA allows representative monitoring by job classification using Similar Exposure Groups. You must monitor enough workers in each SEG to characterize the group's exposure. If exposures within a SEG are highly variable, additional monitoring or individual dosimetry may be warranted.
Always-Current Noise Exposure Data
Soundtrace continuous monitoring eliminates the scheduling burden of periodic dosimetry campaigns — your noise data stays current automatically.
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