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Preventing HazardousNoise and Hearing Lossduring Project Designand OperationPrevention throughDesign (PtD)Prevention through Design (PtD)can be defined as designing outor eliminating safety and healthhazards associated with processes,structures, equipment, tools, orwork organization. The NationalInstitute for Occupational Safetyand Health (NIOSH) launched aPtD initiative in 2007. The missionis to reduce or prevent occupationalinjuries, illnesses, and fatalities byconsidering hazard prevention inthe design, re-design, and retrofit ofnew and existing workplaces, tools,equipment, and work processes[NIOSH 2008a,b].Contents Why is PtD Needed Summary Description of Exposure Workers at Risk Exposure Limits Protecting Workers fromHearing Loss Case Studies Recommendations Acknowledgments ReferencesWhy is PtD Needed? Description ofExposureIntegrating PtD concepts into business processes helps reduce injury andillness in the workplace, as well as costsassociated with injuries. PtD lays thefoundation for a sustainable culture ofsafety with lower workers’ compensationexpenses, fewer retrofits, and improvedproductivity. When PtD concepts are introduced early in the design process, resources can be allocated more efficiently.SummaryExposure to high noise levels in theworkplace can cause hearing loss andaffect worker productivity and compensation costs. This document describescase studies in which noise controlswere implemented that reduced workernoise exposure. NIOSH recommendsconsidering PtD concepts and incorporating engineering noise controls duringthe project design phase of processesand operations.Prolonged exposure to high noise levelscan cause hearing loss and tinnitus.Other health effects include headaches,fatigue, stress, and cardiovascularproblems [Yueh et al. 2003]. High noiselevels can also cause workers to be distracted and interfere with communication and warning signals. If workers donot hear warning signals, they may nottake precautions to prevent hazards orinjuries [NIOSH 1996, 1998; Yoon et al.2015; Cantley et al. 2015].Workers at RiskAn estimated twenty-two million workers are exposed to potentially damaging noise each year [NIOSH 2014a].Although any worker can be at riskfor noise-induced hearing loss in theworkplace, workers in agriculture, mining, construction, manufacturing andutilities, transportation, and the militaryare at greater risk [Masterson et al. 2013;NIOSH 2001].DEPARTMENT OF HEALTH AND HUMAN SERVICESCenters for Disease Control and PreventionNational Institute for Occupational Safety and Health

Exposure LimitsIn the United States, occupational regulations and standards were establishedto protect workers against the healtheffects of exposure to hazardous substances and agents when certain values,or limits, are reached. NIOSH establishesrecommended exposure limits (RELs)for various hazards, but those limits arenot enforceable by law; they are basedon best available science and practices.The REL for noise is 85 decibels, usingthe A-weighting frequency response overan 8-hour average, usually referred toas time-weighted average (TWA); exposures at or above this level are consideredhazardous [NIOSH 1998]. The Occupational Safety and Health Administration(OSHA) sets legally-enforceable permissible exposure limits (PELs) that requireemployers to take actions to reduce workerexposures. The OSHA PEL for noise is 90dBA as an 8-hr TWA [29 CFR* 1910.95].Occupational standards specify a maximum allowable daily noise dose, expressedin percentages. For example, a person exposed to 85 dBA per NIOSH or 90 dBA perOSHA over an 8-hour work shift, will reach100% of their daily noise dose. The noisedose is based on both the sound exposurelevel and how long it lasts (duration) so foreach increase of 3-dB (NIOSH) or 5-dB(OSHA) in noise levels, the duration of the*Code of Federal Regulations. See CFR inReferences.exposure should be cut in half (these arereferred to as exchange rates in standards).Table 1 illustrates the relationship betweensound exposure levels and durations forboth NIOSH and OSHA.The Mine Safety and Health Administration (MSHA) PEL for miners is 90 dBA.If a miner’s noise exposure continues toexceed the PEL despite the use of engineering and administrative controls, themine operator must continue to use theengineering and administrative controls toreduce the miner’s noise exposure to as lowa level as is feasible [30 CFR § 62.130].is the most effective way to reduce noiselevels in the workplace [NIOSH 2001].According to the hierarchy of /), such measures take precedence overusing personal protective equipment suchas earplugs [NIOSH 2015].Protecting Workersfrom Hearing LossCase StudiesNoise-induced hearing loss (NIHL)is 100% preventable; however, onceacquired, it is permanent and irreversible [NIOSH 1998]. Understanding andminimizing the risks are the keys topreventing noise-related injuries andhearing loss. Eliminating or loweringfacility and equipment-related noise at thesource reduces the risks related to NIHLand results in improved safety, productivity, and comfort [Tak et al. 2009].The best way to reduce noise exposure andreduce resulting hearing loss is to addressnoise at the source by considering PtDprinciples. “Engineering out” hazardousnoise found in the workplace before theexposure occurs (e.g., by installing quieterequipment or building an acoustic barrier)Table 1. The average sound exposure levels needed to reach themaximum allowable daily dose of 100%Time to reach100% noise doseExposure levelper NIOSH RELExposure levelper OSHA PEL8 hours85 dBA90 dBA4 hours88 dBA95 dBA2 hours91 dBA100 dBA1 hour94 dBA105 dBA30 minutes97 dBA110 dBA15 minutes100 dBA115 dBAThese noise reduction measures can lowercosts associated with workers’ compensation for hearing loss, protect workers’hearing, and improve productivity. Costsassociated with retrofitting noisy equipment are also no longer necessary.The following case studies demonstratehow small design and operational changescan reduce noise levels and reduceassociated costs.Case Study 1Compressed air is often the most common noise source in manufacturing plantsand other industries. It is used to operateequipment, such as air cylinders, air valves,solenoids, etc., or move parts/product,blow off debris, close flaps on corrugatedcontainers (boxes/cases), or perform similar service-type actions. The noise generated by compressed air is caused by turbulence from the mixing of gases with widelydifferent velocities, particularly when thehigh-velocity air stream flows into therelatively still surrounding air. Additionalturbulence is created as the compressed airblows against objects, such as parts or sections of the machinery.Compressed air noise can be controlledby reducing the air velocity to as low aspractical while maintaining performancerequirements and by treating all openended discharge lines and ports, includingstandard air jets and nozzles with commercially-available quiet-design nozzles orpneumatic silencers [IRSST 2015].Addressing the noise produced by compressed air provides the greatest noisereduction per dollar invested, and can evenhave a payback in dollars through energysavings and life expectancy of equipment.Blowing compressed air through a 3/8-inchopen pipe at a pressure of 71.5 pounds per

square inch (psi) uses 109 standard feetper cubic minute (scfm). At an averagecost of 0.015 per 35.3 standard cubic feet(scf), and an estimated use time of 40%,this equates to 704 hours of consumptionper year. Therefore, the annual cost for theopen pipe is: 109 ft3/min x 0.015/35.3 ft3 60 min /hr 704 hours 1956.44. By using a quiet-design nozzle that provides thesame air-flow service, but only uses 55.9scfm, the resulting annual cost would be 1003.35, a savings of 953.09 per nozzlewhile reducing noise levels by 20 dBA[Driscoll 2011].This approach was successfully demonstrated by two of the Safe-in-Sound Excellence in Hearing Loss Prevention Award (www.safeinsound.us) recipients. One ofthe recipients (Colgate-Palmolive Company) created a guidance document to optimize system operation, minimize air leaksand provide guidance on appropriate use ofair tools. (http://www.safeinsound.us/swf/colgate/). This effort involved (1) measuring, documenting, and optimizing airpressure settings for all pneumatic devices,(2) maintaining the pneumatic equipmentand monitoring the optimized settingsover time, and (3) locating and repairingcompressed air leaks from cracked hoses,failed seals, etc. At the beginning of theimplementation phase, worker doses werereduced from 113 to 90 dBA 8-hr TWA,and energy consumption was also reduced.This was also one of the approaches takenby another Safe-in-Sound recipient (UnitedTechnologies) (http://www.safeinsound.us/swf/UTC/index.html) who reduced workernoise doses from 90 to 85 dBA†.Case study 2A NIOSH investigation of the sound levelsin the truck cab of an air-rotary drilling rig(see Figure 1) found that workers had exposure levels between 91 to 112 dBA. Testswere conducted to identify and isolate thedominant noise sources. Isolating the causeof the in-cab noise indicated that vibrationswere transmitted from multiple hydraulicpumps to the control panel producing theMore information about the awards andproceedings from the conference can befound in Meinke et al. 2013.†Figure 1. Track mounted, air rotary drill rigdominant spike in the sound level spectrum. The researchers also conducted fieldtests to evaluate noise controls to reducein-cab sound levels. Hydraulic noise suppressors were successfully used to reducethe structure-borne noise that is transmitted from the structure to the control panel.Further, the hydraulic noise suppressorsand enhanced soundproofing lessened therisk of hearing loss for workers by reducing the in-cab exposure levels by as muchas 4 dBA at high idle and by 1 dBA whenthe rig was hammer drilling. Covering agap at the cab/inside door interface withlead-fiberglass blankets further reducednoise levels by 3 dBA compared withbaseline conditions [Yantek et al. 2007].Case study 3Continuous mining machines are usedto cut and gather coal. These machinescontain an onboard conveyor consistingof a chain with flight bars that drag thecoal along the base of the conveyor system.The traditional machine chains and flightbars generate excessive noise when theyvibrate against the metal base. Becauseof the higher noise levels, mine operatorsworking near these machines are at greaterrisk of developing NIHL. The flight barsand the conveyor belt tail rotor were coatedwith a thick, durable urethane coating toreduce noise and improve the lifespan ofthe equipment. The redesigned chain andflight bars reduced sound levels by 6-7dBAat the operator ear. The reduction in noiseallowed the noise exposure to remainwithin the MSHA PEL [NIOSH 2009].RecommendationsTo reduce the incidence and severity ofwork-related hearing loss, NIOSH recommends hearing conservation programsfor all workplaces with noise levels thatexceed the REL of 85 dBA. In most cases,the preferred approach to reduce noise inthe workplace is to eliminate or reduce thesource of noise and to follow the hierarchyof controls [NIOSH 2014b; 2015]. NIOSHrecommends the following at each stage ofthe design process:Conceptual Design: Identify and applyrelevant noise control regulations, consensus standards, and codes to establishproject noise emission goals.