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Engineering controls are OSHA's preferred method for reducing occupational noise exposure -- and when exposures exceed the 90 dBA PEL, they are required before hearing protection can serve as the primary protective measure. Yet many employers default immediately to earplugs and earmuffs, either because they are unaware of the control hierarchy or because they have never conducted a formal engineering control feasibility assessment. This guide covers what OSHA requires, what controls are available, and how to document feasibility decisions.
Soundtrace provides the noise monitoring data -- by area, task, and shift pattern -- that engineers and safety managers need to identify where engineering controls will have the greatest impact on employee TWA exposures.
When exposures exceed 90 dBA TWA, OSHA requires employers to implement feasible engineering and administrative controls before relying on hearing protection. Feasibility has two dimensions: technical (can the control work?) and economic (is the cost reasonable?). Both must be evaluated and documented.
OSHA 1910.95(b)(1) states that when employees are exposed to sound exceeding the permissible noise exposures in Table G-16, feasible administrative or engineering controls shall be utilized. If such controls fail to reduce sound levels within the permissible levels, personal protective equipment shall be provided and used to reduce sound levels within the levels of the table.
This language establishes a clear hierarchy: controls first, hearing protection second. The requirement applies when TWA exposures exceed 90 dBA -- not at the 85 dBA action level, which triggers the hearing conservation program but not the mandatory control requirement.
▶ Bottom line: Above 90 dBA TWA, OSHA requires engineering controls -- not just hearing protection. Hearing protection supplements controls that don't fully achieve the PEL; it does not substitute for controls that were never attempted.
| Control Type | Examples | Noise Reduction Potential |
|---|---|---|
| Source controls | Equipment replacement, machine damping, lubrication, balancing rotating parts | High -- addresses root cause |
| Path controls | Acoustic enclosures, barriers, sound-absorbing materials, isolation mounts | Medium to high |
| Receiver controls | Enclosed operator cabs, noise refuges, sound-dampened control rooms | Medium -- protects specific workers |
| Distance | Repositioning workers farther from noise sources | Low to medium (3 dB per doubling of distance) |
Administrative controls reduce noise exposure by managing how workers interact with noise sources rather than by modifying the sources themselves. Common approaches include: job rotation to limit individual cumulative exposure, scheduling high-noise tasks during periods with fewer workers present, restricting worker access to high-noise areas unless required, and designating noise refuge areas for breaks.
Administrative controls are effective in combination with engineering controls but are generally insufficient alone to reduce exposures from well above the PEL to compliance levels.
OSHA does not define specific thresholds for technical or economic feasibility, but an employer's feasibility determination should be documented and defensible. The evaluation should include: the specific control options considered, their estimated noise reduction, the cost of implementation, the employer's financial capacity, and the conclusion reached. An employer who documents a good-faith feasibility analysis is in a stronger position in an enforcement action than one with no documentation at all.
▶ Bottom line: Document every engineering control evaluation -- what was considered, what was rejected and why, and what was implemented. Undocumented decisions look like no decision was made.
When feasible engineering and administrative controls reduce noise but do not bring exposure to at or below the 90 dBA PEL, hearing protection must make up the remaining reduction. The HPDs selected must provide sufficient attenuation to reduce effective exposure to at or below the PEL -- and for employees with confirmed STSs, to at or below 85 dBA.
OSHA requires employers to implement feasible engineering and administrative controls when exposures exceed the 90 dBA PEL. Hearing protection is required in addition to -- not instead of -- feasible controls. At the action level (85 dBA), engineering controls are not required but are preferred in the hierarchy.
OSHA defines feasibility in two dimensions: technical feasibility (can the control physically reduce noise to the required level?) and economic feasibility (is the cost reasonable relative to the employer's resources and the degree of hazard?). Both must be evaluated. A control that is technically feasible but economically infeasible for a small employer may not be required; one that is economically feasible but doesn't achieve sufficient reduction may need to be combined with other controls.
Engineering and administrative controls must be used to the extent feasible to reduce noise exposures to at or below the PEL (90 dBA TWA). If feasible controls reduce exposure but not to the PEL, hearing protection must be used to reduce the remaining exposure.
Yes. If an employer determines that certain engineering controls are not feasible, that determination should be documented in writing -- the rationale, the controls evaluated, and the conclusion. This documentation protects the employer if OSHA questions why controls were not implemented.
Administrative controls -- job rotation, scheduling adjustments, noise refuge areas -- can reduce individual TWA exposures but are rarely sufficient on their own to bring exposures to the PEL without engineering controls or hearing protection. They are most effective as a complement to engineering controls.
Soundtrace noise monitoring gives you facility-level and task-level exposure data -- the foundation for any engineering control feasibility assessment.
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