Construction noise exposure and daily dose

Noise risk depends on level and time

Construction noise is rarely one steady sound for an entire shift. A worker may use a saw for part of the morning, spend time beside a compressor, then work near impact tools or a concrete breaker. OSHA’s construction standard compares sound level and exposure duration. Under Table D-2 of 29 CFR 1926.52, the permissible duration decreases as the sound level rises: for example, the table lists 8 hours at 90 dBA, 4 hours at 95 dBA, 2 hours at 100 dBA, and 1/2 hour at 110 dBA.

A short loud task can contribute a large share of the day’s exposure. Hearing risk is not assessed by averaging the loudest task with quiet time or by checking whether the worker can still hear conversation. Measure or estimate exposures using an appropriate occupational noise assessment. If workers move between tasks, record each sound level and duration so the combined daily dose can be evaluated. A single reading beside the tool does not describe every worker’s exposure.

Combine exposures with the dose formula

OSHA requires the combined effect of periods at different noise levels to be considered. The construction standard calculates an exposure factor by adding each period’s duration divided by the permissible duration at that level: Fe = T1/L1 + T2/L2 + … . Here T is the time actually spent at a level, and L is the table’s allowed duration for that level. A total greater than 1 means the exposure exceeds the table limit.

Example: a worker spends 2 hours at 100 dBA, where the table allows 2 hours, and 4 hours at 92 dBA, where it allows 6 hours. The combined factor is 2/2 + 4/6, or about 1.67. The daily combination exceeds 1 even though neither task lasted its full shift allowance. For actual compliance evaluations, use calibrated instruments and the measurement method required by OSHA; a hand calculation is a planning aid, not a substitute for exposure assessment.

Also account for impulse and impact noise. OSHA’s construction rule states that exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level. Demolition, pile driving, and metal-on-metal impacts can create brief peaks that casual measurements miss. Select an instrument and sampling method suited to the evaluation. If a task generates intense impulses, increase distance, use barriers, and confirm that hearing and eye protection fit the work.

Control noise at its source

When exposure exceeds the table values, OSHA requires feasible administrative or engineering controls. Engineering controls can include quieter equipment, mufflers, vibration isolation, acoustic enclosures, barriers, sound-absorbing materials, or maintaining worn equipment. Administrative controls can reduce the time a worker spends near a loud source, move the task, or schedule noisy work when fewer employees are nearby. Choose controls that reduce the noise reaching workers rather than relying only on warnings after exposure occurs.

Controls must fit the actual task. An enclosure that blocks required ventilation or creates a struck-by hazard is not a good solution. A barrier may protect nearby trades but leave the operator exposed. Maintain equipment, select quieter products when purchasing, and coordinate noisy tasks with other trades. Recheck exposure after a control is installed because a partial enclosure, changed production rate, or different tool can affect the result.

Select and use hearing protection correctly

If feasible controls do not reduce sound levels within the table limits, OSHA requires appropriate personal protective equipment to be provided and used. Hearing protection must fit the worker and the task. Earplugs need correct insertion; earmuffs need a complete seal without interference from hard-hat suspension, eyewear, or respirator straps. Workers may need different protection in hot, dusty, or communication-intensive work. Keep protectors clean, replace damaged products, and train workers on use and limitations.

Hearing protection should not be used to justify avoidable high exposure. It also does not automatically make a hazardous area safe for communication or alarms. Consider how workers will hear spotters, reversing alarms, fire signals, and instructions. When hearing protection is worn, use visual signals or radios where needed and verify that the protective device remains compatible with other PPE.

Protect workers beyond the tool operator

Noise spreads across a jobsite. Workers who do not operate a saw or breaker can still receive high exposure if they work nearby for long periods. Map where trades work, identify high-noise zones, and notify crews before noisy operations start. Use barriers and controlled access where practicable. Include delivery drivers, laborers, and visitors who enter the area. Shared sites need coordination so one contractor’s noise-producing task does not expose another contractor’s workers without their knowledge.

A continuing effective hearing-conservation program is required in construction when exposures exceed the values in Table D-2. Follow the construction requirements and applicable state-plan rules; do not assume the general-industry program provisions apply in exactly the same way. Document the noise assessment, controls, PPE, and worker instruction. Where a state OSHA plan applies, check whether its standard is more stringent.

Measure and respond to changing work

Noise changes when equipment ages, blades dull, materials change, barriers move, or multiple tools run together. Reassess after a new task or equipment change and when employees report ringing ears or trouble hearing. Use a sound-level meter or dosimeter appropriate to the evaluation. Keep a record of instrument settings, calibration, worker location, task duration, and conditions, so another person can understand how the conclusion was reached.

A practical review asks: what are the loud sources, who is exposed, how long does each exposure last, what controls are feasible, and how will protection be checked? If the calculated daily factor exceeds 1, take action rather than waiting for a complaint. Hearing loss often develops gradually and cannot be reversed. Early measurement and task redesign are easier than trying to fix the problem after years of exposure.