Water Well Journal
Issue link: http://read.dmtmag.com/i/715953
A fter determining workers' exposure to noise, interven- tion may be needed to reduce noise exposures to what are allowable levels. There are three ways to reduce exposure to noise, listed here in order of preference: • Engineering controls • Administrative controls • Personal protective equipment (PPE) When engineering controls are not feasible to reduce expo- sures, administrative controls and PPE should be used—and all three are discussed here. This column describes common noise sources and possible noise control solutions. Engineering Controls Engineering controls are any modification or replacement of equipment, or related physical change at the noise source or along the transmission path, that reduces the noise levels at the employee's ear. Octave band analyzers, sound level meters that divide noise into its frequency components, determine the type of frequency a piece of equipment produces and clarify the type of modifications needed. Engineering controls should be the first order of protection and not include the use of hearing protection. There are different sources of workplace noise that could be targeted and modified, such as: • Vibrating surfaces (engines, electric motors, fans) • Mechanical impacts (hammering, pile driving, grinding) • Pulsating gas flow (pistons, jackhammers, pneumatic tools) • Compression and rarefaction of a medium as sound passes through it (gears meshing, fan blades pushing and pulling air) • Air flowing over a surface Refer to Table 1 for common sources of noise and possible solutions. When trying to modify the amount of noise through engi- neering controls, three areas need to be targeted: the source of the noise, the path of the noise, the receiver of the noise. The source of the noise can be modified or redesigned to produce less noise or at different frequencies. The source can be relocated to a protected location or a distant location to reduce the amount of noise. Noise can also be reduced by altering the path it takes. Its transmission can be blocked by using an enclosure or a bar- rier. Material can be placed around the perimeter of the equip- ment to absorb the noise. Workers—the ones on the receiving end of the noise—can likewise be sheltered within an enclosure to prevent the noise from reaching them. Also, if practical, they can be relocated too. Other factors to consider when determining appropriate engineering controls are structure-borne noise, reflected noise, and direct noise transmission. Checking and improving vibration insulation may reduce structure-borne noise that results from vibrations of rotating or vibrating equipment. Increasing the absorption on the area may reduce reverberation, and thus eliminate reflected noise. The noise source may be separated from its surroundings by using a screen or a sound-insulating hood lined with sound- absorbing material. Administrative Controls Administrative controls involve changes in work schedule or operations that reduce workers' exposure to noise. Exam- ples may include: providing training to employees, posting signs in high-noise areas, restricting employees from working in specific high-noise areas, developing written procedures, and conducting periodic hearing tests for employees. Establishing controls and making changes should not result in more workers being exposed to noise. In other words, rotat- ing workers in and out of high-noise areas is not a recom- mended control strategy. The number of workers in the noisy area should be limited. The time spent in the high-noise area should be minimized. Quiet lunch rooms and break areas should be provided for workers. Personal Protective Equipment (PPE) PPE for noise exposure consists of hearing protectors such as earplugs and earmuffs. Hearing protection devices are used to reduce the level of noise that reaches the middle and inner ear when suggested engineering and administrative controls aren't workable or don't sufficiently reduce noise exposure below allowable limits. When selecting hearing protectors, the device should: • Reduce the noise to acceptable levels • Fit the ears • Be checked periodically for fit • Be comfortable SAFETY MATTERS CONTROLLING NOISE A plan for reducing noise levels is a must for contractors. JEROME E. SPEAR waterwelljournal.com 48 September 2016 WWJ