The Ears Have It: Noise & Hearing Protection
According to OSHA, some 22 million workers are exposed to potentially damaging noise at work each year. Last year alone, in fact, U.S. businesses paid more than $1.5 million in penalties for not protecting workers from noise. And, although it’s not comparable to put a number on the toll of a person losing their hearing, it’s estimated that workers’ compensation paid out for hearing loss disabilities is estimated at $242 million.
Such injuries include temporary or permanent hearing loss and can create physical and psychological stress; reduce productivity; and interfere with communication and concentration. It can also contribute to workplace accidents and injuries by making it difficult to hear warning signals.
The US Occupational Safety and Health Administration (OSHA) regulates workplace noise by requiring companies to limit the exposure of their workers to high noise levels. In order to ensure that workers are protected in environments with high noise levels (i.e., greater than OSHA-required levels), there are some critical elements to understand.
OSHA Noise Regulations
Noise and hearing conservation is addressed in specific standards for recordkeeping and general industry. To be specific, section 5(a)(1) of the OSH Act, often referred to as the General Duty Clause, requires employers to “furnish to each of his employees’ employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees.” (This section also can be used to address hazards for which there are no specific standards, such as noise in agricultural operations.)
Many individual state standards exist, as well. There are 28 OSHA-approved, so-called State Plans that operate state-wide occupational safety and health programs. State Plans are required to have standards and enforcement programs that are at least as effective as OSHA’s and some might have different or even more stringent requirements.
Occupational noise exposure is addressed specifically by OSHA’s Subpart G–Occupational health and environmental control-1910.95, Occupational noise exposure. Its directives include Enforcement Guidance for Personal Protective Equipment in General Industry; Hearing Conservation Program; and Occupational Noise Exposure; Hearing Conservation.
OSHA requires an employer to administer a hearing conservation program whenever employees are exposed to noise levels that are at or above an 8-hour, time-weighted average (TWA) of 85 dB (the so-called “Action Level”) or, equivalently, a dose of 50% of the maximum permissible level of 90 dB. This 8-hour TWA is also known as an “exposure action value.” Exposures longer than 15 minutes 100 dB are not recommended. Regular exposure of more than one minute 110 dB risks permanent hearing loss.
Minimum requirements of a hearing conservation program include a monitoring program, an audiometric testing program, hearing protection devices, employee training and education, and recordkeeping. Deciphering OSHA noise regulations can be daunting, to say the least.
There are some companies devoted to helping employers do just that. For example, Sonic-Shield can assist by performing tests and analyses to determine compliance with OSHA noise guidelines and implementing effective soundproofing to reduce exposure of employees to high noise levels. In some cases, it might be possible to reduce noise levels sufficiently to eliminate OSHA requirements for a hearing conservation program, thus improving productivity, ensuring employee health and resulting in significant savings.
A sound survey is often completed to determine areas of potential high noise exposure. A noise screening is used to determine which areas are higher than 80 dB A. For these areas, an official sound survey will take place. This is normally completed using a sound level meter (SLM). Noise monitoring is generally completed using a noise dosimeter that integrates “all continuous, intermittent and impulsive sound levels” to determine a person’s noise exposure level.
Surveys must be repeated when there are significant changes in machinery and/or processes that would affect the noise level. It is believed that engineering controls and administrative controls are ranked as the most effective protection from noise. Engineering controls are measures taken to reduce the intensity of noise at the source, or between the source and a person exposed to the noise, while administrative controls are limitations around noise sources that limit length of noise exposure.
Interestingly, the EU requires a hearing conservation program be implemented when worker exposure levels exceed 80 dBA TWA. This is stricter than hearing conservation regulations in the U.S.
If engineering controls fail to maintain an 8-hour TWA below 85 dBA, then a hearing protection device (HPD) is mandated by OSHA. There are two general types of HPDs: earplugs and earmuffs. Each one has its own benefits and drawbacks. An industrial expert can usually help with the selection of what type of proper HPD must be worn (OSHA requires that HPDs are free of charge).
There are four general classes of earplugs: pre-molded, formable, custom molded and semi-insert.
Premolded earplugs don’t require the plug to be formed before it is inserted into the ear. This prevents the plugs from becoming soiled before insertion.
Formable earplugs are made of a variety of substances, but all are able to be shaped by the user prior to insertion. Advantages include the fact that the device forms to the individual user’s ear; something premolded earplugs cannot do. However, they have the disadvantage of requiring the user’s hands be clean before molding/insertion.
Custom-molded ear plugs are cast from each user’s own ear canals. Therefore, they provide a personalized, individualized fit.
Semi-inserts usually consist of a soft earplug on the end of band. The band helps maintain the earplug’s position. A big advantage is that they can be quickly inserted and removed.
The main difference between earmuffs and earplugs is that earmuffs are not inserted inside the ear canal. Instead, earmuffs create a seal around the outside of the ear, to prevent noise from reaching the inner ear. Earmuffs are easy to wear and often provide a more consistent fit than an earplug.
There are earmuffs available that use the principle of active noise control to help reduce noise exposures. However, the protection earmuffs offer can be mitigated/interfered with by large sideburns or glasses, causing the seal of the earmuffs to be broken.
The fit of a hearing protector is very important, as well, because if the HPD is not worn properly, the NRR is meaningless. There are now fit testing devices on the market that will verify a proper fit of an HPD. Products that will verify proper fit include: 3M EARFit Validation System, FitCheck, FitCheck Solo, INTEGRAfit, SafetyMeter and VeriPro. Fit-test systems provide a Personal Attenuation Rating (PAR) that is currently dependent upon the company that manufactures the fit-testing system. Most fit test systems provide an A-weighted PAR, which means that the attenuation can be subtracted from the A-weighted noise exposure assessment of the employee or hearing protector user.
Noise reduction ratings
The EPA requires that all hearing protection devices be labeled with their associated noise reduction rating (NRR). The NRR provides the estimated attenuation of the hearing protection device. However, it has been found that the “labeled manufacturers’ noise reduction ratings (NRRs) substantially overestimated the actual field attenuation performance.” [Park, MY; Casali, JG (December 1991).”A controlled investigation of in-field attenuation performance of selected insert, earmuff, and canal cap hearing protectors.”]
As a result of that study, OSHA recommends that 7 dB be subtracted from the NRR to determine the amount of noise reduction afforded by a hearing protection device. The NRR is generally given in a C-weighted format, so to obtain the A-weighted reduction, one must subtract 7 dB. OSHA also recommends a 50% safety factor; therefore, the final OSHA recommended reduction would be (NRR-7)/2. Fit testing companies and sound-survey companies can help employers ensure their workers’ ears are protected and help keep them in compliance with regulations.
The Uvero Test Kitchen at Lantos Technologies serves both industry and government with its Lantos 3D Ear Scanning System. The company has developed custom-fit hearing protection.
In addition to devices for noise reduction, many companies produce acoustic panels that can be made for industrial use. These high performance, durable and versatile panels increase the intelligibility of speech; mitigate distracting, unpleasant and even intolerable auditory conditions; and can decrease the risk of harm from exposure to excessive noise. For example, Eckel’s pre-engineered acoustic panels come in a range of sizes and styles and can be readily positioned within the host room to achieve optimal noise reduction performance. Available in aluminum or steel, they can be customized and finished to fit and complement any architectural layout. Easy to install during new construction or as a retrofit item, acoustic panels can be an economical and effective means to controlling noise. WMHS