Hazard Analysis — Noise
Workers who load and unload material, members and components may be exposed to noise.
Noise-induced hearing loss (NIHL). A worker who is repeatedly exposed to noise at 85 decibels or above without hearing protection is at risk for serious hearing loss. Noise-induced hearing loss is 100 percent preventable but once acquired, hearing loss is permanent and irreversible.
How do we hear?
Hearing is a series of events in which the ear converts sound waves into electrical signals that are sent to the brain and interpreted as sound. The ear has three main parts: the outer, middle, and inner ear. Sound waves enter through the outer ear and reach the middle ear where they cause the eardrum to vibrate. The vibrations are transmitted through three tiny bones in the middle ear, called the ossicles. These three bones are named the malleus, incus, and stapes (and are also known as the hammer, anvil, and stirrup). The eardrum and ossicles amplify the vibrations and carry them to the inner ear. The stirrup transmits the amplified vibrations through the oval window and into the fluid that fills the inner ear. The vibrations move through fluid in the snail-shaped hearing part of the inner ear (cochlea) that contains the hair cells. The fluid in the cochlea moves the top portion of the hair cells, called the hair bundle, which initiates the changes that lead to the production of nerve impulses. These nerve impulses are carried to the brain, where they are interpreted as sound. Different sounds move the hair bundles in different ways, thus allowing the brain to distinguish one sound from another, such as vowels from consonants. Continuous exposure to loud noise can damage the structure of the hair cells, resulting in hearing loss and tinnitus (ringing in the ears).
NIHL can be caused by a one-time exposure to loud sound as well as by repeated exposure to sounds at various loudness levels over an extended period of time. The loudness of sound is measured in units called decibels. For example, normal conversation is approximately 60 decibels, the humming of a refrigerator is 40 decibels, and heavy city traffic noise can be 85 decibels. Examples of sources of loud noises that cause NIHL are motorcycles, firecrackers, and firearms, which emit sounds over 120 decibels. Sounds of less than 80 decibels, even after long exposure, are unlikely to cause hearing loss.
People with hearing loss often become socially isolated because they cannot communicate easily with others. They also may not be able to hear warning signals, and so may have an injury.
For more information, please see:
NIOSH Noise Topics
Noise and Hearing Damage in Construction Apprentices
Level of Risk:
Exposures are of such a magnitude and character that all or most workers risk developing serious long- or short-term health effects.
Who gets hearing loss from noise?
From 1999-2004 the University of Washington Department of Environmental and Occupational Health Sciences measured noise exposure among nine trades. Construction workers overall were exposed over 85 dBA in about 70% of work shifts using a NIOSH exposure standard. The NIOSH standard is more sensitive to intermittent and variable noise, and because of that is a better representation of the actual risk of hearing loss in construction. If we were to use the OSHA method, the percentage of work shifts over 85 dBA falls to 29.5%.
Among Iron Workers, the average exposure was 91.1 dBA with the NIOSH method, and 75.6% of the shifts averaged above 85 dBA as a time weighted average. This study did not sample exposures to iron workers’ tools specifically but did identify the ten noisiest tasks and tools.
According to NIOSH, approximately 30 million workers are exposed to hazardous noise on the job. While any worker can be at risk for noise-induced hearing loss in the workplace, construction workers often have high exposures to dangerous levels of noise. Most construction workers have significant hearing loss from noise by the time they are 50 years old. Examination programs for construction workers have found that hearing loss (defined as material impairment using the NIOSH formula) was found in:
- 50% of 6500 construction workers who had been employed at DOE facilities
Most people's hearing gets worse as they get older. But for the average person, aging does not cause impaired hearing before the age of 60. People who are not exposed to noise and are otherwise healthy keep their hearing for many years. People who are exposed to noise and do not protect their hearing begin to lose their hearing at an early age. By age 25, for example, the average carpenter has the same hearing as someone who is 50 years old and has worked in a quiet job.
How can you tell if you are exposed to high levels of noise? If you work in a noisy area and have to raise your voice to talk to someone who is an arm's length away, then the noise is likely to be hazardous. If your ears are ringing or sounds seem dull or flat after leaving a noisy place, then you probably were exposed to hazardous noise.
Researchers at the University of Washington have measured noise levels in many construction tasks. They found that the average level was 81.4 DBA for all workers in all trades. The tables below give more detail on noise levels and hazards for Masonry tasks and tools.
Noise exposure in construction
|Trade TWAs||Mean dBA||% shifts >85 dBA|
|Sheet Metal Worker||85.7||82.0%|
|All Workers Combined||87.8||64.7%|
Ten loudest tasks, in order of increasing average noise level
|Tasks (Trade)||Average Noise Level (DBA)||Maximum Noise Level (DBA)||% time hearing protection worn when needed|
|Installing Trench Conduit (Electricians)||95.8||118.6||0%|
|Operating Work Vehicle (Bricklayers)||98.0||116.7||75%|
|Operating Manlift (Operating Engineers)||98.1||117.6||N/A|
|Welding, Burning (IronWorkers)||98.4||119.7||6%|
|Operating Scraper (Operating Engineers)||99.1||108.6||100%|
|Laying Metal Deck (Ironworkers)||99.6||119.9||75%|
|Grinding (Masonry Trades)||99.7||118.6||49%|
|Operating Bulldozer (Operating Engineers)||100.2||112.5||100%|
|Chipping Concrete (Laborers)||102.9||120.3||N/A|
Ten loudest tools, in order of increasing average noise level
|Tools||Average Noise Level (dBA)||Maximum Noise Level (dBA)||% time hearing protection worn when needed|
|Welding, Cutting Equipment||94.9||122.8||4%|
|Other Hand Power Tool||95.4||118.3||11%|
|Hand Power Saw||97.2||114.0||25%|
|Screw Gun, Drill Motor||97.7||123.7||29%|
|Stationary Power Tool||101.8||119.8||67%|
|Power Actuated Tool||103.0||112.8||81%|
(This table is provided courtesy of the University of Washington, Department of Environmental and Occupational Health Sciences.)
The OSHA standards for controlling noise in the construction industry are not as stringent as those in general industry. Although the construction standard says the noise level should not exceed 90 dB, it does not require regular hearing tests for construction workers.
- Is the noise at my workplace so loud that I have to raise my voice signficantly for someone an arm's length away to hear me?
- When I leave work to a quieter environment, do my ears feel plugged?
- Or do I hear a mild ringing or whooshing noise that goes away after an hour or two?
If you answer yes to any of these questions, your workplace is too noisy.
At the NIOSH site for occupational noise exposure you can find information on assessing noise exposure at work.
Detailed information on measurement of noise exposure can be found in this NIOSH document http://www.cdc.gov/niosh/topics/noise/default.html.
For information on NIOSH noise measurements on your specific power tools, see http://wwwn.cdc.gov/niosh-sound-vibration/.
OSHA does not require hearing testing for construction workers, but construction employers are required to comply with the OSHA noise standard; the standard also contains details on noise measurement. OSHA Noise page. Consensus standards applicable to noise in the construction industry can be purchased from the American National Standards Institute (ANSI).
Regulations & Standards:
OSHA standard 1926.52 sets the permissible noise exposure at 90 dBA for an 8 hour day in construction. As the noise level increases, the permissible exposure time decreases:
TABLE D-2 - PERMISSIBLE NOISE EXPOSURES
|Duration per day (hours)||Sound level (dBA slow response)|
|1/4 or less||115|
The standard does not require audiometry. OSHA has issued a notice of proposed rule making which would update the standard to include a hearing conservation program, as is required for general industry, but a revised standard has not yet been issued. Details on the standard and the proposed revision can be found here http://www.osha.gov/SLTC/noisehearingconservation/index.html
Both ACGIH and NIOSH consider 8 hr exposures to noise at 85dBA to be hazardous. At the noise levels of most power tools (100-110 dbA) the OSHA allowable exposure times are eight to ten times greater than the NIOSH hazard-based limits (http://www.cdc.gov/niosh/docs/98-126/pdfs/98-126.pdf).
Regulations adopted by a state must be at least as protective as the corresponding federal standard. Work may also be subject to rules of other federal, state and local agencies. Even where there is no hazard specific standard, OSHA provides a general duty for the employer to provide a work site free from recognized hazards.
Federal OSHA Standards are enforced by the U.S. Department of Labor in 26 states. There are currently 22 states and jurisdictions operating complete State plans (covering both the private sector and state and local government employees) and 5 - Connecticut, Illinois, New Jersey, New York and the Virgin Islands - which cover public employees only. If you are working in one of those states or jurisdictions you should ensure that you are complying with their requirements.