Audiometry: A Guide to Workplace Noise Levels
Excessive workplace noise can wreak havoc on employees — here's what you need to know about keeping them safe.
Every year in the United States, at least 22 million workers are exposed to noise levels high enough to cause permanent hearing loss. Of these, 19% have suffered some degree of hearing loss that impacts their day-to-day activities. Unfortunately, most of this hearing loss is permanent, and workplace noise levels cause much of it.
For many employers, the government mandates hearing loss prevention programs. Fortunately, there are approaches any employer can take to mitigate or even eliminate employee hearing loss. Here is what you need to know.
The Effects of Excessive Noise
Permanent hearing loss is one effect of exposure to excessive workplace noise, but there are others. Short term exposure can also lead to tinnitus, a permanent or semi-permanent condition where sufferers hear a persistent ringing in their ears. Physical and psychological stress is another side effect of excessive noise that can decrease employee productivity, communication and focus. It can also lead to increased workplace accidents and injuries as workers fail to hear warning signals. The effects of permanent hearing loss can be life-altering, severely impairing the ability to communicate.
How Loud is Too Loud?
The Occupational Safety and Health Administration (OSHA) sets the legal limit for noise exposure in the workplace. Known as Permissible Exposure Limits (PEL), these limits are averaged over an eight-hour workday, and OSHA's permissible level of noise is 90 dBA for this eight-hour time span. The dBA measurement represents units of sound pressure known as decibels (dB) measured on A-weighted (A) sound levels that measure how the human ear perceives loudness. OSHA also sets an additional exchange rate of 5 dBA, which essentially means that every time the noise level increases by 5 dBA, the amount of time a worker can be exposed to the specific noise level is cut in half.
While OSHA set the legal limits, the National Institute for Occupational Safety and Health (NIOSH) has also weighed in by recommending that noise exposure for all workers be limited to 85 dBA over an eight-hour period. They also recommend a reduced exchange rate of 3 dBA.
These noise limits are reached relatively easily in many workplaces and within many industries. To give an idea of what these limits mean, city traffic or a noisy restaurant can also reach 85 dB. By contrast, a steel mill or riveting machine registers at 110 dB and a chainsaw at 120 dB.
Measuring Noise Levels
Employers must carefully monitor noise levels in their workplace. This can be done with a sound level meter (SLM). Free SLMs, in the form of smartphone apps, are available from a variety of sources and NIOSH offers a free SLM for download on their website. The SLM, which usually includes a filter for A-weighting, is sufficient for most workplaces. However, it is limited to measuring instantaneous noise.
Workplaces with intermittent or variable noise levels, or where workers are consistently changing location, may want to use a noise dosimeter. The dosimeter is a small, lightweight device worn by a worker that has a microphone clipped to the worker's collar near the ear. This device records the average noise levels the worker is exposed to while wearing the device, giving a more thorough picture of potentially hazardous situations.
The integrating sound level meter (ISLM) is another handheld device like the SLM, but it provides data that is similar to the dosimeter.
Hearing Conservation Programs
In general industry settings, Hearing Conservation Programs are mandated when workers are exposed to time-weighted average noise levels of 85 dBA or higher over an eight-hour shift. This program includes mandated monitoring of noise levels. If noise levels consistently exceed allowable limits, employers must institute mitigating practices that include appropriate personal protective equipment (PPE), training and education and ongoing testing for hearing loss known as audiometry.
PPE, including noise reduction or noise cancelling devices, must be provided to workers free of charge. Employers must train workers on the appropriate use of PPE and monitor usage on an ongoing basis. They must also make an additional effort to retrain or re-educate staff if they fail to use PPE or fail to use it correctly.
Training and Education
According to OSHA guidelines, training and education efforts must include the effects of noise on hearing over the long and short term. It must also cover the purpose, advantages and disadvantages of hearing protection devices as well as the selection, fit and care of devices. It's always a good idea to include additional mitigating factors in your education efforts, such as exposure to noise outside of work and early warning signs of hearing loss. Finally, you must ensure your employees are aware of both the purpose and procedures related to audiometric testing. Further training may also be required based on the results of annual audiometric testing.
What Is Audiometric Testing?
Audiometric testing monitors hearing over time and is a requirement for businesses exposing workers to high levels of noise. Testing must be provided free of charge, and employers must communicate the results to their employees. A licensed physician oversees these tests, which begin with a baseline audiogram administered at least fourteen hours after exposure to workplace noise. Employees then receive yearly audiograms, which are compared to the baseline test.
If a standard threshold shift (STS) is detected, indicating hearing loss that the overseeing physician deems to be caused by workplace noise, the employer must follow strict additional procedures. These include:
- Providing employees not currently wearing hearing protection with properly fitted PPE and training in the use and care of this PPE
- Ensuring employees already wearing appropriate PPE are re-fitted and retrained
- Securing PPE that offers greater protection if necessary
- Referring employees for further testing as appropriate
Finally, employers must maintain accurate and detailed records of noise exposure measurements for two years and audiometric test results for the duration of a worker's employment.
There are additional steps employers can take to mitigate the risk of hearing loss for employees.
- Use engineering controls and design controls such as barriers and isolation of exceptionally loud equipment to control volumes and exposure. Consider routing traffic to avoid unnecessary exposure.
- Consider modifications to equipment designed to reduce noise levels and ensure sound levels are key criteria in the purchase of new equipment and tools.
- Post warnings in areas of high noise levels.
- Institute administrative controls that provide breaks and reduce exposure.
- Consider alternative employment for those suffering demonstrable damage to prevent damage from worsening.
- Empower workers to take mitigating actions and to report areas of concern.