In the United States alone, about 22 million workers are exposed to hazardous noise at work every day. In addition to contributing to hearing loss, excessive noise prevents workers from hearing warning signals, negatively affects communication between workers, and decreases workers’ ability to concentrate. It’s also been linked to stomach problems and high blood pressure.
The National Institute for Occupational Safety and Health (NIOSH) recommends that workers not be exposed to noise amounting to more than 85 decibels for 8 hours, but there’s no doubt that reducing the noise levels as much as possible is ideal. How can employers do this? Read on to find out.
Sources of Noise in the Workplace
Many workplaces have areas where excessive noise is a problem for employees. Some of the most common sources include:
- Manufacturing equipment
- Power generators
- Heavy equipment
- Motor vehicles
- Hammers and jackhammers
- Drills and other power tools
- Construction site activity
Unlike changes in temperature, it's not possible for humans to become acclimated to high noise levels. But hearing loss happens gradually, so workers often don't notice it until it's too late.
(Learn more about Noise: The Safety Hazard 22 Million Workers Are Exposed to Every Year.)
There are three factors that contribute to noise, each of which must be considered when determining what type of exposure to noise a worker receives.
- Intensity or loudness: measured by a noise level meter and described in decibels (dB)
- Frequency: the most damaging frequencies are between 3,000 and 4,000 Hz
- Duration: how long an employee is exposed to noise
Noise Reduction Techniques
Hearing protection devices are an important part of PPE for workers in noisy environments, but reducing the noise to begin with is the best strategy. PPE should always be the last line of defense.
Industrial hygienist Jeffrey Birkner notes that determining what is necessary involves three key steps:
- Recognizing that a noise problem may exist
- Evaluating the extent of the problem
- Controlling the problem
With respect to the third step, NIOSH recommends that employers adopt a noise reduction approach based on the hierarchy of hazard control, which focuses on five key actions, in this order:
- Eliminating the hazardous noise
- Substituting loud equipment for a quieter alternative
- Introducing engineering controls to reduce noise to safer levels
- Using administrative controls to reduce exposure to hazardous noise
- Providing PPE to protect workers from high noise levels
We’re going to focus on the first three – techniques that eliminate, substitute, or reduce noise that can seriously damage workers’ hearing and potentially contribute to other health issues.
(Learn about The Hierarchy of Hazard Controls.)
Opt for Quiet Tools and Machinery
Low-noise tools and machinery are available, and NIOSH’s Buy Quiet program encourages employers to choose these when replacing old equipment or starting a new business. While there isn’t always a noise score displayed on equipment, you can call the manufacturer to inquire about this information.
Compare the scores before deciding on the equipment you want to purchase to effectively control noise from the outset.
Substitute for Lower-Noise Options
Good substitutions include electric instead of pneumatic tools, presses rather than hammers, hydraulic presses instead of mechanical ones, and belt conveyors in place of roller conveyors.
Substitute Machine Parts
In some cases, simply changing up one part of a machine can offer a significant reduction in noise. For example, replacing spur gears with helical gears or straight-edged cutters with spiral cutters usually reduces noise by about 10 dB.
Also consider replacing metal gears with plastic ones, gear drives with belt drives, and steel or solid wheels with pneumatic tires.
Modify the Energy Source
This is often the most effective way to reduce noise in the workplace. For example, reducing peak impact force of a punch press will significantly reduce the noise generated, even if it means the press has to run for a longer period of time.
Maintain Equipment Correctly
Improper or insufficient maintenance can cause tools and machinery to produce more noise than they should.
There are two types of maintenance: corrective and preventive. Corrective (or reactive) maintenance is necessary when something isn’t working right, while preventive maintenance is carried out at predetermined intervals to reduce the chances of equipment failure occurring (e.g. cleaning, lubrication, inspection). Engaging in preventive maintenance is a good way to keep the equipment running as quietly as it can.
Isolate the Source of Noise
By keeping the noise in one specific area, employers can protect other workers from exposure and the resulting hearing damage. Even noise levels that are below exposure limits can be irritating, causing stress and impacting worker performance. Solutions include designing an insulated room or even simply installing a sound wall or curtain, behind which the noise-producing equipment sits.
PPE: The Last Line of Defense
If you’ve done all of the above and still need to further protect workers, PPE offers one final line of defense. If worn properly, hearing protection like earplugs and earmuffs can be extremely effective.
Hearing protection devices are ranked using a Noise Reduction Rating (NRR). Since different employees have different needs, each worker should be able to select the type of hearing protection that they find most effective and comfortable. This helps ensure that the protection will be worn instead of cast aside due to discomfort or ineffectiveness.
(Learn more in Hearing Protection PPE: Beyond the Basics.)
With research showing that 2.53 healthy years are lost per 1,000 noise-exposed workers every year, noise reduction in the workplace isn’t an option.
In many cases, there are effective ways to significantly lower the level of noise that employees are exposed to using quieter equipment or simple part substitutions. Maintenance is a key part of any good noise reduction strategy, and isolating the noise can also be helpful to reduce exposure.
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