Plant floor problems · Modular Offices
85 dBA is the line. What to enclose, what to curtain, and what an STC rating means
Reviewed September 25, 2026. Official sources are linked where they exist.
Short answer
OSHA 1910.95 sets the permissible exposure limit at 90 dBA as an eight-hour time-weighted average and requires a hearing conservation program once exposure reaches 85 dBA. The engineering options are to enclose the source, separate the people, or absorb the reflections. Standard modular office panels are typically rated around STC 30 to 31, which makes normal speech inaudible but leaves loud machinery audible; sound-rated panel options go higher. Industrial sound curtains are commonly rated in the 10 to 15 dB reduction range. Enclosing a single loud machine usually costs less than protecting everyone around it.
The rule
Table G-16 in 1910.95 sets the permissible exposure at 90 dBA for eight hours, with shorter allowed durations at higher levels. At an eight-hour average of 85 dBA, the action level, the employer must run a hearing conservation program: monitoring, audiometric testing, hearing protection, training, and records. Engineering controls that bring the exposure down are what the standard prefers over protection worn by the worker.
What STC means and what to expect
Sound Transmission Class is a laboratory rating of how much airborne sound a wall assembly blocks; the higher, the better. As a rough guide, STC 25 to 30 leaves normal speech audible, 35 muffles loud speech, 40 is a common target for private offices, and 45 is very good. Standard quick-ship modular office panels with a gypsum or polystyrene core are published around STC 30 to 31. Higher-rated panels exist; ask for the tested rating for the specific panel rather than a range. Field performance is always lower than the lab number because doors, seals, and openings leak, which is why we specify the whole room.
| STC 25 to 30 | Normal speech audible through the wall; standard panel offices sit here |
|---|---|
| STC 35 | Loud speech muffled |
| STC 40 | Common target for private offices |
| STC 45 and up | Very good; loud machinery reduced to background |
Three ways to bring the number down
Enclose the source: an acoustic enclosure built around a compressor, a press, or a test cell, with an absorptive inner face, sealed doors, viewing windows, and silenced ventilation. Separate the people: a sound-rated office or quiet pod for the supervisor and the quality tech. Absorb the reflections: sound curtains and baffles that cut the reverberant field; curtains are typically rated in the 10 to 15 dB reduction range with noise reduction coefficients around 0.75 to 0.85. A noise survey tells you which one pays first.
Questions buyers ask
- At what noise level do I need a hearing conservation program?
- At an eight-hour time-weighted average of 85 dBA, under 1910.95. The permissible exposure limit is 90 dBA.
- Will a modular office block machine noise?
- Standard panels at about STC 30 to 31 make speech private but leave loud machinery audible. Sound-rated panels and sealed doors do much better. Tell us the noise you are dealing with and we specify the panel.
- Enclosure or curtain?
- Enclose a single loud source. Curtain an area where the problem is many sources and reverberation. Curtains are also the answer where the equipment has to stay accessible.
Do your own research
Official sources first. We link the rule, not a summary of the rule, wherever one exists.
- 29 CFR 1910.95 Occupational noise exposure
OSHA
Permissible exposure limits and the 85 dBA action level for hearing conservation.
What we quote for this
Modular Offices
Acoustic Enclosure for Machines and Test Cells
A sound-rated modular room built around a noisy machine or test cell, with access doors, windows, and ventilation.
- Size
- Built to the machine footprint plus service clearance
- Wall system
- Sound-rated panels with absorptive inner face; STC per panel selection (verify)
- Doors
- Sealed personnel door; removable panels or double doors for machine access
Modular Offices
Quiet Pod and Phone Booth, Plant Floor
A sound-rated one- or two-person room for calls, video, and focused work next to the line.
- Size
- 4' x 6' single; 6' x 8' two-person
- Wall height
- 8'
- Wall system
- Sound-rated panels; STC per panel selection (verify)
Doors
Warehouse Divider Curtains and Work Zones
Track-mounted industrial curtains that split a floor into zones for dust, temperature, noise, or process separation.
- Height
- Up to the roof deck; typical 10' to 30'
- Material
- Vinyl, insulated, sound-absorbing, or fire-rated per use
- Track
- Ceiling- or structure-mounted roller track