An estimated 22 million workers each year are exposed to noise loud enough to cause hearing damage.¹ Additionally, 24% of all hearing difficulty among U.S. workers is due to occupational exposure.² Reducing the exposure to noise begins with understanding the issue, effects and causes.

We would like to introduce you to some of the common noises in the workplace, the necessary hearing protections, and the steps you can take to protect your workers.

A Brief Introduction to Hearing and Hearing Loss

When sound waves enter the outer ear, the vibrations impact the ear drum and are transmitted to the middle and inner ear. In the middle ear three small bones called the malleus (or hammer), the incus (or anvil), and the stapes (or stirrup) amplify and transmit the vibrations generated by the sound to the inner ear.

The inner ear contains a snail-like structure called the cochlea, which is filled with fluid and lined with cells with very fine hairs. These microscopic hairs (stereocilia) move with the vibrations and convert the sound waves into nerve impulses–the result is the sound we hear. If these hairs are damaged, this is how hearing loss occurs.

Measurement of Sound

Noise is measured in units of pressure, called decibels, named after Alexander Graham Bell, using A-weighted sound levels (dBA), which match the perception of loudness by the human ear.

How is this measured? The physics behind decibel measurement is 10 log (P2/P1) dB where the log is to base 10. To put this into context, consider this:

On the decibel scale, the smallest audible sound (near total silence) is 0 dB.

  • A sound 10 times more powerful is 10 dB.
  • A sound 100 times more powerful than near total silence is 20 dB.
  • A sound 1,000 times more powerful than near total silence is 30 dB.

Here are some common sounds and their decibel ratings:

  • Near total silence – 0 dB
  • A whisper – 15 dB
  • Normal conversation – 60 dB
  • A lawnmower – 90 dB
  • A car horn – 110 dB
  • A rock concert or a jet engine – 120 dB
  • A gunshot or firecracker – 140 dB

Considering the limits of the human body, 85-90 dB will result in hearing loss, 140 dB will cause immediate damage, and according to a study by Jurgen Altmann, 200 dB would cause your lungs to rupture.

For detailed information on this, please look at Optimum Safety Management Hearing Protection page.

NIOSH and OSHA Permissible Exposure Limits (PELs)

Now that you know how hearing works, and what it would take to kill a worker, what do you need to know about your own workplace? The National Institute for Occupational Safety and Health recommends that all worker exposures to noise should be controlled below a level equivalent to 85 dBA for eight hours to minimize occupational noise induced hearing loss.

Adopted by OSHA, permissible sound exposure levels are as follows (29 CFR 1910.95(b)(2)):

TABLE G-16 – PERMISSIBLE NOISE EXPOSURES (1)
Duration per day, hoursSound level dBA slow response
890
692
495
397
2100
1.5102
1105
0.5110
<0.25115

 

The Average Sounds on the Job

What’s that sound? It could be OSHA knocking, if you aren’t protecting your workers from hazardous noise.

Here are some of the common sounds you or your workers may hear on the job. Compare them to the above table to see if you are adequately protecting your employees.

Carpentry Tools

Mitre Saw102 dBA
Hand Drill98 dBA
Chop Saw106 dBA
Hammer Drill114 dBA
Metal Shear96 dBA
Hain Saw109 dBA
Impact Wrench102 dBA
Skill Saw100 dBA
Belt Sander93 dBA
Tile Saw101 dBA
Circular Sander90 dBA
Router95 dBA
Planer93 dBA
Table Saw92 dBA
Mortissing90 dBA

For information on the dB levels emitted by common power tools, check out the NIOSH PowerTools Database

 

Average Heavy Equipment Noise Levels

Heavy-duty bulldozer97-107
Vibrating road roller91-104
Light-duty bulldozer93-101
Asphalt road roller85-103
Laborers78-107
Crawler crane < 35 ton (non-insulated cab)93-101
Crawler crane >35 ton (non-insulated cab)
Crawler crane >35 ton (insulated cab)
90-98
80-89
Rubber-tired crane >35 ton (non-insulated cab)
Rubber-tired crane >35 ton (insulated cab)
78-90
59-87
Tower Crane70-76

Source: ELCOSH

Average Construction Noise Levels

Pneumatic chip hammer103-113
Jackhammer102-111
Concrete joint cutter99-102
Skilsaw88-102
Stud welder101
Bulldozer93-96
Crane90-96
Earth Tamper90-96
Hammer87-95
Gradeall87-94
Front-end loader86-94
Backhoe84-93

Source: CPWR – Center for Construction Research and Training

Sources: Decibel Chart from Haas Eaton, OSHAX, Purdue University,

Sound Levels by Industry

Industrial BranchLAeq dB(A)LCpeak dB(C)
Foundry93127
Plastic packing83112
Metal packing92119
Printing press93119
Shipyard92134
Brewery96117
Porcelain fabric88128
Glass factory95113
Glass fibers factory97101
Confectionery factory86106
Weaving factory95119
Stretch factory88114
Paper mill92130
Saw mill94123
Copper tube factory96126

Source:

World Health Organization Noise Report

Additional Sources:

¹Exposure to Hazardous Workplace Noise and Use of Hearing Protection Devices Among US Workers

²Occupational Hearing Loss Exposure

See part 2, featuring hearing protection advice and insights.

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