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Prevention through Design: NIOSH Issues Report on Preventing Hazardous Noise and Hearing Loss
Release Date: January 14, 2016
Prevention through Design (PtD) can be defined as designing out or eliminating safety and health hazards associated with processes, structures, equipment, tools, or work organization. In 2007, the National Institute for Occupational Safety and Health (NIOSH) launched a PtD initiative, and the recent 2016 publication Preventing Hazardous Noise and Hearing Loss during Project Design and Operation is its latest effort to promote PtD to eliminate or control occupational noise exposures.
The report emphasizes that the best way to reduce noise exposure and resulting hearing loss is to address noise at the source by considering PtD principles. “Engineering out” hazardous noise found in the workplace before the exposure occurs (e.g., by installing quieter equipment or building an acoustic barrier) is the most effective way to reduce noise levels in the workplace and takes precedence over the use of hearing protection, which is the least desirable control method. PtD noise reduction measures can protect worker hearing, lower workers’ compensation costs, improve productivity, and eliminate the need to retrofit equipment.
Three case studies are included in the report, illustrating the use of PtD concepts to control noise associated with the use of compressed air, air-rotary drilling rigs, and continuous mining machines:
- Compressed air use: Noise from compressed air use, one of the most common noise sources in the workplace, can be controlled by reducing the air velocity to as low as practical while maintaining performance requirements and by treating all open-ended discharge lines and ports, including standard air jets and nozzles with commercially-available “quiet-design” nozzles or pneumatic silencers. Using quiet nozzles can also have a financial impact, and the report provides a sample calculation of how fitting an open-ended pipe with a quiet nozzle can result in savings of $953.09 per year per nozzle while lowering the noise levels by 20 dBA.
- Air-rotary drilling rigs: A NIOSH investigation of the sound levels in the truck cab of an air-rotary drilling rig found that workers had exposure levels between 91 to 112 dBA. Hydraulic noise suppressors were successfully used to reduce the structure-borne noise that is transmitted from the rig structure to the control panel. Further, the hydraulic noise suppressors and enhanced soundproofing lessened the risk of hearing loss for workers by reducing the in-cab exposure levels by as much as four dBA at high idle and by one dBA when the rig was hammer drilling. Covering a gap at the cab/inside door interface with lead-fiberglass blankets further reduced noise levels by three dBA compared with baseline conditions.
- Continuous mining machines: These machines, which are used to cut and gather coal, contain an onboard conveyor consisting of a chain with flight bars that drag the coal along the base of the conveyor system. The traditional machine chains and flight bars generate excessive noise when they vibrate against the metal base. Because of the higher noise levels, mine operators working near these machines are at greater risk of developing noise-induced hearing loss. In this study, the flight bars and the conveyor belt tail rotor were coated with a thick, durable urethane coating to reduce noise and improve the lifespan of the equipment. The redesigned chain and flight bars reduced sound levels by 6-7dBA at the operator’s ear. The reduction in noise allowed the noise exposure to remain within the Mine Safety and Health Administration (MSHA) Permissible Exposure Limit (PEL).
NIOSH recommends the following PtD concepts for noise control at each stage of the design process:
- Conceptual Design: Identify and apply relevant noise control regulations, consensus standards, and codes to establish project noise emission goals.
- Preliminary Design: Assess the risk for noise hazards, factoring in noise from various sources that can affect workers’ overall noise exposures and develop risk control alternatives. Identify noise sources and work processes that have the potential to contribute to a worker’s overall noise exposure. Eliminate or reduce potential noise sources by substituting quieter processes, elements, parts, and equipment.
- Buy Quiet: Implement a Buy Quiet program and set design specifications regarding noise levels to be adhered to in equipment purchasing decisions. Develop equipment specifications to be included in procurement documents. Develop test protocols for factory acceptance testing and commissioning.
- Procurement: In accordance with Buy Quiet program implementation, ensure noise levels of all equipment purchases are specified by the manufacturer. Gather and compare like model equipment noise levels, specifications, and pricing from equipment suppliers. Accounting for operational needs and level of commitment to Buy Quiet initiatives, execute appropriate purchases. Ensure that purchased equipment meets design specifications and does not exceed maximum noise levels as specified.
- Commissioning: Conduct noise tests to ensure that specified noise levels have been achieved. Consider including this testing in factory acceptance tests. All test measurements should be made with manufacturer-recommended operating conditions.
- Start-up and Ongoing Operations and Maintenance: NIOSH recommends that noise surveys be conducted to ensure that noise levels do not exceed the NIOSH Recommended Exposure Limit (REL) of 85 dBA sound pressure level. Develop standard operating procedures (SOPs) to maintain noise controls and ensure worker noise exposures are controlled as new equipment is introduced or existing equipment is modified. Equipment noise levels should be noted post-maintenance and periodically in the Buy Quiet documentation.
Integrating PtD concepts into business processes helps reduce injury and illness in the workplace, as well as costs associated with injuries. PtD lays the foundation for a sustainable culture of safety with lower workers’ compensation expenses, fewer retrofits, and improved productivity. When PtD concepts are introduced early in the design process, resources can be allocated more efficiently.
Preventing Hazardous Noise and Hearing Loss during Project Design and Operation can be accessed at http://www.cdc.gov/niosh/docs/2016-101/pdfs/2016-101.pdf. In addition, see the NIOSH PtD website at http://www.cdc.gov/niosh/topics/PTD/ and the NIOSH noise control website at http://www.cdc.gov/niosh/topics/noisecontrol/default.html.
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