A facility noise map is a spatial representation of noise levels across a work environment — showing where noise is above or below OSHA 1910.95 thresholds and helping identify which workers need HCP enrollment. According to the CDC, approximately 22 million U.S. workers are exposed to hazardous occupational noise annually — and facility noise mapping is among the most effective first steps to identifying which of them need OSHA 1910.95 HCP enrollment. A well-executed noise map is the foundation for defensible noise monitoring, systematic HPD selection, engineering control prioritization, and WC liability reduction.
A Tier 2 automotive parts supplier used grid-based area SLM measurements to build a facility noise map across their 180,000 sq ft stamping and welding floor. The map revealed that two assembly cells adjacent to a high-speed press — not part of the originally identified HCP population — measured 87–89 dBA TWA. The 14 workers in those cells had never been enrolled in the hearing conservation program. Post-mapping dosimetry confirmed enrollment eligibility. More importantly, four of those 14 workers had been with the company for 5+ years — meaning potential STS accumulation during a period of no audiometric monitoring, and a corresponding WC documentation gap.
What a Facility Noise Map Is and What It Produces
A facility noise map plots sound level measurements across a facility floor plan, creating a visual record of the acoustic environment. At minimum, it should show:
- Measurement points across the facility grid
- dBA readings at each point (typically from area SLM measurements during representative production conditions)
- Color-coded zones: green (below 80 dBA), yellow (80–84 dBA), orange (85–89 dBA), red (90+ dBA)
- Location of significant noise sources (machinery, HVAC, compressed air systems)
- Work areas and typical worker positions
The map itself is not a compliance document — it is a planning and screening tool. Individual worker dosimetry is required to establish enrollment-level TWA for workers in or adjacent to high-noise zones. But the noise map is the most efficient first step to identify where dosimetry is needed.
How a Facility Noise Map Supports OSHA 1910.95 Compliance
OSHA 1910.95(d) requires employers to monitor all employees “whose noise exposures may equal or exceed the action level.” The noise map is the systematic method for identifying which workers “may equal or exceed” the action level — it operationalizes the exposure screening requirement before individual dosimetry is conducted. Without a noise map or equivalent systematic screening, employers risk missing workers who should be enrolled, particularly those adjacent to high-noise areas rather than directly operating noise-producing equipment.
How to Build a Facility Noise Map
- Obtain or create a facility floor plan at a scale that allows measurement point annotation. CAD drawings, architectural plans, or hand-drawn floor plans all work.
- Establish a measurement grid at regular intervals (typically 10–20 feet in production areas, wider spacing in lower-noise zones).
- Conduct area SLM measurements at each grid point during representative production conditions — all equipment running, typical staffing, typical product and process.
- Record A-weighted dBA readings at each measurement point. Use slow response, A-weighting. Take measurements at approximately ear height (1.5m) at each grid point.
- Plot results on the floor plan using color coding or contour lines to show noise zones.
- Identify worker positions within each zone and flag workers in zones at or above 80 dBA for personal dosimetry follow-up.
Grid Measurement Methodology
| Zone Level | dBA Range | Grid Spacing | Follow-Up Action |
|---|---|---|---|
| Low noise | Below 75 dBA | 20–30 ft grid adequate | No HCP screening required; document for baseline |
| Moderate | 75–79 dBA | 15–20 ft grid | Consider voluntary program; document for WC defense |
| Elevated sub-threshold | 80–84 dBA | 10–15 ft grid | Personal dosimetry to confirm individual TWA; voluntary HCP enrollment recommended |
| Action level | 85–89 dBA | 10 ft grid; tight at source margins | Personal dosimetry required; HCP enrollment if TWA confirmed at or above 85 dBA |
| PEL zone | 90+ dBA | Dense grid; perimeter of source | Personal dosimetry required; engineering control evaluation; mandatory HPDs |
From Noise Map to Personal Dosimetry
The noise map identifies areas; dosimetry identifies individuals. Workers in zones above 80 dBA should receive personal dosimetry to determine their individual 8-hour TWA. This is especially important for:
- Workers who move between zones during the shift — their TWA reflects the time-weighted combination of all areas visited
- Workers near but not at noise sources — 3–6 dB distance attenuation can change enrollment eligibility
- Workers in borderline zones (82–87 dBA area readings) — individual dosimetry resolves enrollment decisions
See: Area Monitoring vs. Personal Noise Monitoring: When to Use Each.
Keeping the Map Current
A noise map is accurate only for the production conditions and equipment configuration at the time of measurement. It must be updated when:
- New equipment is installed or existing equipment is replaced
- Production layout is changed
- Line speeds or process parameters change significantly
- Engineering controls are added, modified, or removed
These are the same triggers as the OSHA 1910.95(d)(3) re-monitoring requirement. Integrating noise map updates into the facility’s management of change process ensures both requirements are addressed simultaneously.
Documentation and Retention
Retain the noise map along with measurement logs documenting: date and time of measurements, production conditions, instrument make/model/serial/calibration, weather conditions (for outdoor measurements), and the individual dBA readings at each measurement point. OSHA 1910.95(m)(3) requires noise monitoring records to be retained for at least 2 years. Best practice is to retain noise maps indefinitely as part of the facility’s compliance history.
Frequently Asked Questions
OSHA 1910.95(d) requires employers to monitor employees whose noise exposures may equal or exceed the action level. A noise map is the most systematic method for determining which workers “may” be at that level, but OSHA does not mandate a specific mapping methodology. The map supports the monitoring obligation — it is not itself the compliance document.
Area noise maps are typically built using a Type 1 or Type 2 integrating sound level meter (ANSI S1.4) set to A-weighting and slow response. The SLM is placed at grid measurement points at ear height and readings are taken during representative production conditions. Readings are then plotted on the facility floor plan.
Any process change, equipment replacement, or layout modification that may affect noise levels should trigger a map update — consistent with the 1910.95(d)(3) re-monitoring requirement. At minimum, reviewing the map for accuracy annually is good practice, even if no changes have occurred.
Noise monitoring and mapping integrated with HCP enrollment
Soundtrace links facility noise monitoring data directly to worker HCP enrollment records — ensuring that any worker whose exposure meets the action level is automatically flagged for program enrollment and audiometric testing.
Get a Free Quote