Scope of Noise Exposure
The number of advertisements about hearing aids should tell you that hearing loss is a common issue in America. Estimates are that 48 million Americans have some degree of hearing loss. About 5% of adults have a hearing loss that could be classified as disabling.
Hearing loss is considered to be a disability as it affects your normal life activities. Hearing loss is permanent and cannot be restored. Noise is an exposure that exists outside of work and in many cases, there are exposures outside work that are more intense than workplace noise levels.
The Occupational Safety and Health Administration, OSHA, has had occupational noise exposure standards in place for decades. This standard applies at work to offer a minimum level of protection against hearing loss.
The American Conference of Governmental Industrial Hygienists, ACGIH, has a noise exposure that is more conservative than the OSHA standard. The National Institute of Occupational Safety and Health, NIOSH, has also published their recommended exposure limits, REL, for noise in the workplace. NISOH provides research for OSHA to consider in its regulation process.
Noise Basics
Noise is the presence of sound pressure levels that can be heard by the human ear. Sound pressure is measured in decibels. Noise can be further characterized by the frequency of the noise. High frequency noise is higher in pitch to the human ear. Lower frequency noise can be heard and also felt. If you have been next to a car at a traffic light you may both hear and feel the bass from the other vehicles’ sound system.
Noise acts on the hair cells in the inner ear. High noise levels can cause a gradual and permanent hearing loss. The higher frequency noises are the first to be affected. The loss of hearing acuity can be difficult on normal living and relationships. It can also be a hazard when you cannot hear warning signals.
To control this hazard, OSHA and NIOSH have developed tables that indicate the acceptable time for exposure to various noise levels. These tables are based on a specific set of noise frequencies that are most susceptible to hearing loss. This set of frequencies is the A scale, and the measurements are expressed as dBA to reflect A scale weighting. A third-party group, the American Conference of Governmental Industrial Hygienists, have also published their own noise exposure standards that align with NIOSH recommendations.
Exposure Limits
A 100% noise dose is a calculated value based on measured noise levels and the time you are exposed to that noise level. OSHA shows its noise dose as a Permissible Exposure Limit, PEL. NIOSH shows its noise dose as a Recommended Exposure Limit, REL. The 100% noise dose is the maximum level of noise that is safe for exposure. As the noise level, in dBA, increases, the time to reach 100% dose decreases. PEL and REL are represented by a Time Weighted Average, which calculates noise dose based on exposure levels in dBA and time that the exposure existed.
The table below shows the variance in OSHA regulations and NIOSH provided research-based exposure limits.
Time to reach 100% noise dose | Exposure level per NIOSH REL | Exposure level per OSHA PEL |
8 hours | 85 dBA | 90 dBA |
4 hours | 88 dBA | 95 dBA |
2 hours | 91 dBA | 100 dBA |
1 hour | 94 dBA | 105 dBA |
30 minutes | 97 dBA | 110 dBA |
15 minutes | 100 dBA | 115 dBA |
To put these noise levels into context, here are example sources that generate the noise levels
85 dBA is equivalent to a loud restaurant dining room.
85 dBA – 89 dBA – Hair dryer, blender, power lawn mower, vacuum cleaner, snowblower, garbage disposer, propeller plane 1,000 feet above you
90 dBA –100 dBA emergency siren, pneumatic drill, diesel truck, gas leaf blower, pressure washer
105 dBA – 110 dBA – Rock concert, pile driver, gas hedge trimmers
Over 110 dBA – commercial jet take off, civil defense siren
Most woodworking tools are typically in the 90 dBA to 102 dBA range.
Gunfire noise levels can range between 140 dB – 190 dB
Many smartphones have noise measurement apps available. TWA measurement requires a dosimeter or a detailed spreadsheet to record noise levels across time. The average level calculated by these apps is not a true TWA, but an average should be viewed in context of the time it represents to see if the levels are higher than the above table values for that period.
A good rule of thumb is that if you need to raise your voice to be heard over any noise, the noise level can be high enough to cause hearing loss.
Example noise sources are present in our homes and hearing loss is not solely an occupational issue.
The first step in controlling your exposure to noise is recognizing the hazard. If you do not recognize the hazard, you will not take precautions to protect yourself from the long-term damage from hearing loss.
The Driehaus Difference
We recognize that noise exposures are not simple a workers compensation issue. Hearing loss affects your life and your ability to enjoy everyday experiences. There are noise exposures outside of work that can cause hearing loss. Recognizing the signs of a harmful noise exposure allows you to make choices. Those choices are the topic of the next installation of this article, the controls that can be applied these noise exposures. Call us at 513-977-6860 or reach out using the contact tools on our website, www.driehausins.com. We want to be your insurance provider.
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