Loud Noises: Hearing conservation and protection
Published: February 2015
By Tom O'Connor
On a daily basis, we hear sounds and noise in our environment from a variety of sources, such as television, radio, household appliances and traffic. However, these everyday sounds are usually at a safe volume. The Occupational Safety and Health Administration (OSHA) estimated that, annually, 30 million people are exposed to hazardous occupational noise. The Bureau of Labor Statistics has also reported hundreds of thousands of cases where workers have suffered significant or permanent hearing loss on the job. As a result, noise-related hearing loss is consistently identified as one of the most significant workplace hazards. Fortunately, there are measures that can be taken to help prevent or minimize exposure to hazardous noise.
First, it is important to understand how the ear works. Sound waves create vibrations in the eardrum, which transmits them to the inner ear, where cells with very fine hairs move with the vibrations and convert the sound waves into nerve impulses. The result is the sound we hear.
Loud noise exposure can damage these hairs and result in hearing damage or loss. According to OSHA's Occupational Noise Exposure document, "Loud noise can also create physical and psychological stress, reduce productivity, interfere with communication and concentration, and contribute to workplace accidents and injuries by making it difficult to hear warning signals. Noise-induced hearing loss limits your ability to hear high frequency sounds, understand speech, and seriously impairs your ability to communicate."
Hearing loss can also affect the ability to socialize, creating a challenge for communication. You can tell that noise is a problem in the workplace by ringing or humming in the ears, having to shout to be heard by coworkers in close proximity, or temporary hearing loss after leaving work.
Sound is measured in decibels (dBA), and OSHA sets legal limits on noise exposure in the workplace. The Occupational Noise Exposure document states: "These limits are based on a worker's time weighted average over an 8 hour day. With noise, OSHA's permissible exposure limit (PEL) is 90 dBA for all workers for an 8 hour day. The OSHA standard uses a 5 dBA exchange rate. This means that when the noise level is increased by 5 dBA, the amount of time a person can be exposed to a certain noise level to receive the same dose is cut in half."
The duration of the exposure is as important as the sound level. If the duration is longer or shorter, it changes the maximum noise level to which workers can be exposed. At 95 dBA, the maximum exposure is 4 hours per day and less than one-half hour per day at 110 dBA. Workers should never be exposed to levels above 140 dBA. Even a momentary exposure to this level can cause permanent damage. To put these measurements in perspective, common decibels levels on the job site include 93 dBA for a digger derrick, 97 dBA for a bucket truck and 113 dBA for a ground-rod driver. Given the limits on exposure, workers should not be around a digger derrick for longer than 6 hours or near a ground-rod driver for more than 15 minutes without hearing protection.
Noise controls are a crucial element in protecting workers from hazardous occupational noise, and there are several ways to reduce exposure to these hazards. Even reducing harmful noise by a few decibels can make an immense difference in protecting workers' ears.
One means of reducing hazardous occupational noise is through engineering controls. This involves modifying or replacing equipment and making related physical changes at the noise source to reduce the decibel levels at the worker's ear. Some examples are using low-noise tools and machinery, properly maintaining and lubricating moving parts on machinery and equipment, enclosing/isolating the noise source, and implementing a barrier, such as sound walls or curtains, between the noise source and employee.
Another way to reduce hazardous noise is through administrative controls. This includes modifying the workplace, operating noisy machines during shifts when fewer people are exposed, limiting the amount of time a person spends at a noise source, providing quiet areas where workers can gain relief from hazardous noise sources and mandating worker presence at a suitable distance away from noisy equipment.
Hearing protection devices are also valuable in protecting worker safety. Personal protective equipment, including earmuffs and earplugs, can be an excellent secondary form of hearing protection when engineering or administrative controls are not feasible or able to fully reduce decibel levels to a safe volume.
Finally, OSHA requires employers to put in place a hearing-conservation program when exposures exceed 90 dBA for an 8-hour exposure. According to OSHA, the program is designed, "To help prevent initial occupational hearing loss, preserve and protect remaining hearing, and equip workers with the knowledge and hearing protection devices necessary to protect them."
For more information regarding hearing protection regulations or resources on hearing-conservation programs, visit www.osha.gov.