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Noise Control and Hearing Loss
Permanent & Irreversible, Constant Threat is Preventable

Noise has been a constant workplace threat since the Industrial Revolution. Too much noise exposure may cause a temporary change in hearing (your ears may feel clogged) or a temporary ringing in your ears (tinnitus). These short-term problems usually go away within a few minutes or hours after leaving the noise.

However, repeated exposures to loud noise can lead to permanent, incurable hearing loss. NIOSH recommends removing hazardous noise from the workplace whenever possible and using hearing protectors in those situations where dangerous noise exposures have not yet been controlled or eliminated.

Work-related hearing loss is a critical workplace safety and health issue. The National Institute for Occupational Safety and Health (NIOSH) and the occupational safety and health community named hearing loss one of the 21 priority areas for research in the next century. Noise-induced hearing loss is 100 percent preventable, but once acquired is permanent and irreversible. Therefore, prevention measures must be taken by employers and workers to ensure the protection of workers’ hearing.

“Work-related hearing loss is one of the most common occupational diseases in the United States,” says Dr. Linda Rosenstock, director of the National Institute for Occupational Safety and Health (NIOSH).

According to NIOSH, 30 million Americans are exposed to hazardous noise at work. But these workers don’t have to suffer hearing loss. Supervisors can make changes to the equipment to eliminate or reduce noise. Sometimes, workers can adjust their work schedules and job to avoid being around noisy equipment. Finally, when engineering or administrative controls can’t eliminate exposure, wearing hearing protection devices, such as ear plugs or ear muffs, should be mandatory. Loud noises damage the delicate hair cells in the inner ear. Most of the time this damage happens gradually when prolonged exposure to loud sounds exhausts these hair cells, according to NIOSH. As noise levels increase, the tiny cilia at the top of the hair cells can be injured or broken off. Entire groups of these hair cells can even be torn away. Hair cells don’t repair themselves. So when enough hair cells are damaged, a hearing loss results.

Measuring sound

Sound is measured in decibels. A normal conversation takes place at about 60 decibels. A woodshop noise level is about 100 decibels, and a chainsaw measures about 110 decibels, according to the National Institute on Deafness and Other Communication Disorders (NIDCD). Prolonged exposure to noise above 85 decibels can cause hearing loss.

A short, intense sound—an explosion, for example— may cause immediate hearing loss. But usually hearing loss occurs gradually after prolonged exposure to loud noise. It may occur so gradually you may not even realize you are losing your hearing. Over time, sounds may simply become muffled or distorted.

OSHA requires employers to develop and implement a noise monitoring program when “information indicates that any employee’s exposure may equal or exceed an eight-hour average exposure of 85 decibels.” When this occurs, OSHA requires employers to notify employees, to establish and maintain a hearing test program, and to train workers how to prevent occupational hearing loss. When engineering controls have not yet eliminated hazardous noise, OSHA also requires employers to provide hearing protectors and ensure workers wear them.

For noise measurements to be useful, they need to be related to noise exposure risks or the prioritization of noise control efforts, rather than merely filed away. In addition, the results need to be communicated to the appropriate personnel, especially when follow- up actions are required. Consider:

• Were the essential/critical noise studies performed?
• Was the purpose of each noise study clearly stated? Have noise-exposed employees been notified of their exposures and appraised of auditory risks?
• Are the results routinely transmitted to supervisors and other key individuals? • Are results entered into health/medical records of noise exposed employees? • Are results entered into shop folders?
• If noise maps exist, are they used by the proper staff?
• Are noise measurement results considered when contemplating procurement of new equipment? Modifying the facility? Relocating employees?
• Have there been changes in areas, equipment, or processes that have altered noise exposure? Have follow-up noise measurements been conducted?
• Are appropriate steps taken to include (or exclude) employees in the hearing loss prevention programs whose exposures have changed significantly?

Engineering and Administrative Controls

Controlling noise by engineering and administrative methods is often the most effective means of reducing or eliminating the hazard. In some cases engineering controls will remove requirements for other components of the program, such as audiometric testing and the use of hearing protectors, such as the following:

Expandable Foam Plugs

These plugs are made of a formable material designed to expand and conform to the shape of each person’s ear canal. Roll the expandable plugs into a thin, crease-free cylinder. Whether you roll plugs with thumb and fingers or across your palm doesn’t matter. What’s critical is the final result—a smooth tube thin enough so that about half the length will fit easily into your ear canal.

Some individuals, especially women with small ear canals, have difficulty rolling typical plugs small enough to make them fit. A few manufacturers now offer a small size expandable plug.

Pre-molded, Reusable Plugs

Pre-molded plugs are made from silicone, plastic or rubber and are manufactured as either “one-size-fits-most” or are available in several sizes. Many pre-molded plugs are available in sizes for small, medium or large ear canals.

A critical tip about pre-molded plugs is that a person may need a different size plug for each ear. The plugs should seal the ear canal without being uncomfortable. This takes trial and error of the various sizes. Directions for fitting each model of pre-molded plug may differ slightly depending on how many flanges they have and how the tip is shaped. Insert this type of plug by reaching over your head with one hand to pull up on your ear. Then use your other hand to insert the plug with a gentle rocking motion until you have sealed the ear canal.

Advantages of pre-molded plugs are that they are relatively inexpensive, reusable, washable, and convenient to carry, and come in a variety of sizes. Nearly everyone can find a plug that will be comfortable and effective. In dirty or dusty environments, you don’t need to handle or roll the tips.

Canal caps

Canal caps often resemble earplugs on a flexible plastic or metal band. The earplug tips of a canal cap may be a formable or premolded material. Some have headbands that can be worn over the head, behind the neck or under the chin. Newer models have jointed bands increasing the ability to properly seal the earplug.

The main advantage canal caps offer is convenience. When it’s quiet, employees can leave the band hanging around their necks. They can quickly insert the plug tips when hazardous noise starts again. Some people find the pressure from the bands uncomfortable. Not all canal caps have tips that adequately block all types of noise. Generally, the canal caps tips that resemble standalone earplugs seem to block the most noise.

Earmuffs

Earmuffs come in many models designed to fit most people. They work to block out noise by completely covering the outer ear. Muffs can be “low profile” with small ear cups or large to hold extra materials for use in extreme noise. Some muffs also include electronic components to help users communicate or to block impulsive noises.

Workers who have heavy beards or sideburns or who wear glasses may find it difficult to get good protection from earmuffs. The hair and the temples of the glasses break the seal that the earmuff cushions make around the ear. For these workers, earplugs are best. Other potential drawbacks of earmuffs are that some people feel they can be hot and heavy in some environments.FSM