Controlling Noise

Published On: September 1, 2016By Categories: Safety, Safety Matters

A plan for reducing noise levels is a must for contractors.

By Jerome E. Spear

After determining workers’ exposure to noise, intervention 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 exposures, 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 engineering 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 barrier. Material can be placed around the perimeter of the equipment 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 soundabsorbing material.

Table 1. Common Noise Sources and Possible Solutions

 

Administrative Controls

Administrative controls involve changes in work schedule or operations that reduce workers’ exposure to noise. Examples 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, rotating workers in and out of high-noise areas is not a recommended 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
  • Be compatible with other PPE
  • Be replaced when deteriorated.

There are a variety of styles of hearing protectors and each provides different levels of protection. Earplugs are available as foam, pre-molded, and custom molded earplugs. Hearing protectors are also available as earmuffs.

Consider also wearing canal caps—they resemble earplugs on a flexible plastic or metal band which have flexible tips that plug the ear canal. They don’t extend into the ear canal, they just close the ear opening. Canal caps are ideal for those situations where hearing protection has to be taken on and off frequently.

How to Measure Hearing Protection

The most common way to evaluate hearing protection is the noise reduction rating (NRR). Most manufacturers of hearing protection devices indicate the NRR for their product on the packaging—since the U.S. Environmental Protection Agency requires it.

Appendix B of the Occupational Safety and Health Administration’s occupational noise standard (29 CFR 1910.95) requires that 7 decibels (dB) be subtracted from the NRR whenusing A-weighted sound levels.

A-weighting is applied to instrument-measured sound levels to account for the relative loudness perceived by the human ear and commonly used for the measurement of environmental and industrial noise. A-weighted measurements are expressed as dBA or dB(A).

Scientific literature indicates laboratory-based noise reduction data for hearing protectors are seldom achieved in the workplace. As a result, applying an additional safety factor of 50% is recommended to adjust for workplace conditions.

The National Institute for Occupational Safety and Health’s recommendations for de-rating the NRR are different than OSHA’s protocols. For earmuffs and formable earplugs, NIOSH recommends 25% and 50% be subtracted, respectively, from the labeled NRR. For other earplugs, NIOSH recommends 70% of the manufacturer’s labeled NRR be subtracted.

Wearing dual hearing protection (both earmuffs and earplugs in combination) does not equate to additive protection. Decibels cannot be added together like other numbers. Likewise, the NRRs of both the earmuffs and earplugs cannot be added together.

There are no empirical or theoretically derived equations available that can predict the reduction in noise of an earplug and earmuff combination with sufficient accuracy to be useful. As a rule of thumb, the OSHA procedure of computing the dual protection to add 5 dB to the NRR of the more protective
of the two devices is a reasonable approximation.

Summary

Noise is frequently present above the allowable exposure limits at construction and general industry worksites—that includes well drilling operations. Noise can have both hearing-related and non-hearing-related health effects.

That being the case, preventing excessive exposure to noise is the only way to preserve your hearing. Exposure monitoring can assess exposures to noise. If exposure monitoring results indicate noise levels are above allowable levels, noise control strategies such as practical engineering controls, administrative controls, and PPE should be employed.

Bottom line: There is no cure for noise-induced hearing loss.

DACUM Codes
To help meet your professional needs, this column covers skills and competencies found in DACUM charts for drillers and pump installers. DO refers to the drilling chart and PI represents the pumps chart. The letter and number immediately following is the skill on the chart covered by the column. This column covers: DOD-4, DOD-5, DOK-9, PIB-2, PIE-2, PIE-3, PIG-3 More information on DACUM and the charts are available at www.NGWA.org.

Jerome E. Spear, CSP, CIH, is president of J.E. Spear Consulting and has more than 22 years of experience helping organizations prevent injuries and illnesses, control losses, and achieve regulatory compliance. He held the positions of technical services manager with XL Specialty Risk Consulting and corporate industrial hygiene manager for Chicago Bridge and Iron Co., a worldwide steel fabricator and construction company.

 

 

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