Solution Summary: Noise Control Strategies
Using barriers, maintaining equipment, and moving noisy equipment far as feasible are some noise control strategies.
Description:
Worksite noise should be controlled to an average of below 85 dBA to protect worker hearing. Simple field fixes can significantly reduce noise exposures. Noise can be controlled by:
- Using "silenced" or muffled equipment
- Maintaining equipment and keeping tools sharp
- Locating noisy equipment as far as feasible from work areas
- Not locating noisy equipment near hard reflecting or reverberating surfaces
- Erecting barriers between the noise source and workers
Worksite noise is most effectively and reliably controlled at the source and in its path to the worker, not at the worker's ear.
- Muffled generators and compressors are available from equipment rental centers. Muffled compressors may produce about 75 dBA compared to 90 dBA or more for unmuffled versions.
- Doubling the distance between the noise source and the worker reduces the noise exposure about 6 dBA (3 dBA for linear sources like roads). Each additional doubling yield an additional 6 dBA of reduction. Echoing from exterior walls or interior walls and ceiling can reduce this reduction.
- Simple plywood barriers can yield a 10-12 dBA reduction in noise. The barrier should not have gaps and should be wider and higher than the line of sight between the noise source and the worker.
- Keeping cutting tools sharp and mechanical equipment well maintained reduces noise while cutting job time and operating costs.
Construction tool noise source levels and the measured effect of distance and barriers can be found on eLCOSH
Noise Control: A Guide for Workers and Employers
Another type of noise control strategy is a program called “Buy Quiet” developed by the National Aeronautics and Space Administration (NASA) which was later adopted by the National Institute for Occupational Safety and Health (NIOSH) for the construction and manufacturing sectors. “Buy Quiet” is an occupational noise hazard prevention initiative that recommends selecting and purchasing the lowest noise emitting power tools and machinery in order to reduce the risk of noise-induced hearing loss. As part of this, NIOSH has developed the NIOSH Power Tools Database, a searchable database that provides sound emission levels of powered hand tools.
Risks Addressed:
Hearing loss or deafness due to excessive noise exposure.
How Risks are Reduced:
Noise (sound) is a pressure wave in air. As it moves away from its source the energy is spread over a rapidly growing sphere so it becomes much lower at any given point. Putting a barrier in the way casts a "sound shadow" in the path, lowering the level further..
Noise is measured on a log scale multiplied by ten (that's why its called a deci (ten) bel scale). Every increase of 3 dB means the energy has doubled, an increase of 10 dB equals a ten fold increase, and twenty dB equals a one-hundred-fold increase.
We hear sound change in strength at only a fraction of the actual power of the noise. When we hear a noise as twice as loud as another noise, it is actually about ten times (10dB) as powerful.
Because the ear reacts differently to sounds of different frequencies a measuring scale called dBA has been developed to mimic the ears response. This is the scale used for most noise control work.
Reducing noise at the source (e.g., leasing quieter tools), by moving the noise source further from workers, or by erecting an enclosure or barriers to the noise, will reduce noise exposure. There is extensive research that reducing noise exposure reduced noise-induced hearing loss. Whether the noise exposure is reduced enough to result in significant prevention of hearing loss depends on the site characteristics, and specific actions taken. Some enclosures will be more effective than others.
Effects on Productivity:
Task-specific effects have not been characterized, but poor communication in general reduces productivity.
Controlled studies have found that even high noise levels may increase output in terms of numbers of tasks but errors are more likely to occur and quality is reduce. Tasks involving concentration are more vulnerable to noise disruption than are routine tasks, and intermittent noise tends to be more disruptive than continuous noise. Poor performance may continue after intermittent noise has stopped.
Reduction of noise at the source reduces or eliminates the need for a hearing conservation program.
Overall site safety is enhanced by better communication.
Productivity is improved by better communication and reduced worker stress.
Construction tool noise source levels and the measured effect of distance and barriers can be found on eLCOSH
Additional Considerations:
Also use hearing protection personal protective equipment (PPE), such as plugs and muffs for when adequate noise reduction is not possible.
Availability
Some noise reduction strategies, such as increasing the distance from a noise source to workers, require some planning but do not require any materials. Other noise reduction strategies can be achieved using materials commonly accessible on a construction site such as plywood or foam board enclosures. Although they are available in the market, the lease or purchase of muffled or quieter tools and equipment, require advance planning. For more information, visit: USDOL Noise Control: A guide for workers and employers and NIOSH Power Tools Database
