3M Center for Hearing Protection

Hearing Protection Basics

For most Americans, hearing protection is not an area of concern. It should be. According to the Occupational Safety and Health Administration (OSHA), 22 million workers are exposed to potentially damaging noise levels at work each year, with an estimated $242 million spent annually on hearing loss disability compensation. This is a completely avoidable situation, even in the noisiest corners of the industrial world. Hearing protection is more sophisticated now than ever before, and there are options in design and function to fit any situation.

What is hearing loss, exactly? Our hearing organs are mind-boggling in their size and precision. The tympanic membrane (eardrum—get it?), for example, vibrates within an unimaginably small range of motion, filtering sounds into the middle ear and protecting the whole apparatus from foreign objects. After some complicated acoustic work courtesy of three tiny bones, the sound is funneled into a spiraling tube of fluid called the cochlea, lined with bundles of microscopic hairs that translate vibrations in the fluid to nerve impulses that the brain can understand, completing the process. It is these hairs—the stereocilia—that are destroyed in hearing loss. They do not regenerate, so the resulting damage is permanent. The fact that so many of our workforce are putting their delicate and irreplaceable ears at risk unnecessarily is an invisible crisis in public health.

Every hearing protection product comes with a noise reduction rating (NRR). This value indicates the approximate amount of decibels (dB) that a given product subtracts from the noise entering the ear. For example, if you’re in an environment that consistently has noise above 110 dB, you’ll need a product with an NRR of 20 dB to get it down to a safe level. This is assuming that the product is being used properly. So what is a decibel? Sound waves work by changing the pressure of the air they move through. The resultant pressure difference is measured in decibels. Normal speech averages at 60 dB, while the threshold of pain varies based on many factors, but usually falls between 120 (a typical amp setup at a rock concert) to 140 dB (a jet fighter taking off).
 

Types of Hearing Protection

Headset NRR tends to fall between 22 to 25 dB, and earplugs up to 29 dB. It’s worth noting that wearing earplugs and earmuffs at the same time does not result in a cumulative NRR. 22 dB earmuffs worn over 25 dB earplugs does not add up to 47 dB, although doubling up does improve protection and is recommended for more extreme environments. All devices and ratings assume proper use, so it’s important for employers to show their workers how to fit the plugs.

Hearing protection comes in two basic forms: earplugs and earmuffs.

Earplugs are inserted directly into the ear canal, which provides a mechanical method of blocking noise from reaching and damaging the hearing apparati. They must be inserted properly and adjusted regularly, as they tend to loosen over time. Some designs help to combat this. Banded plugs come are attached to each other by a flexible piece of plastic, which provides a small force that pushes them into the canals. Others come with posts that aid in ear insertion, such as the 3M EasyTouch. Corded plugs have a string that attaches two plugs together so they aren’t separated and can be hung around the neck when not in use.

Earmuffs protect hearing by forming a seal around the outer ear that blocks noise. They come as classic earmuffs and sophisticated headsets. They are easy and quick to apply, do not work loose, and come in a range of sizes, colors, and styles. Various types of ear cup material are used, each meeting different comfort levels without applying direct pressure in the canal. Cap-mounted earmuffs piece directly into hard hats that have side-accessory slots. Earmuff headsets provide the same baseline protection as standard styles, but also offer other advanced features. Using headsets also provides a clear indication of protection use for environments where confirmation is necessary to comply with OSHA guidelines.

There are two main types of hearing protection: passive and active.

Passive hearing protection blocks all sound in an environment. This means that damaging noise is blocked along with ambient sound, such as communication. A common scenario with earmuffs is that the worker will lift one cup off the ear and lean towards someone they are communicating with. Obviously, hearing protection is compromised when this happens.

Active hearing protection provides the same level of baseline noise blockage, but adds environmental microphones that detect ambient sounds and transmit them to speakers inside the ear cup. When the system determines a sound has exceeded the threshold of harm, the noise is either blocked or transmitted at a much lower level. Depending on the needs of the user, these products can also feature audio jacks, automatic shut-offs, and volume control. Active hearing protection is desired when communication is necessary or damaging noise levels are intermittent or pulsing.
Benefits for the Individual
Using hearing protection at work allows you to keep both your career and hearing in optimum condition. The applications go beyond the workplace, though. If you’re at the shooting range, you’re being exposed to around 140 dB going off right next to your eardrum with every shot (depending on the gun), along with the sounds from whoever else is there. Gunfire is easily the most hazardous non-occupational sound level that average Americans encounter, and just like on the job, there’s no reason to do that kind of damage to your hearing. Our products can make it so a passion for sport shooting doesn’t mean sacrificing your ears. For hunters, active-protection headsets can even let you turn up low-frequency sounds so you can hear game approaching from further away than with the naked ear.

Benefits for the Company

As mentioned above, everyone wins when hearing protection is used in the workplace. It creates an organizational culture of attention to safety and health and saves money in hearing loss claims from workers. Hearing loss jurisprudence is a legal minefield. It’s extremely difficult to disprove a worker’s claim that hearing loss resulted from workplace exposure, and many states don’t address the issue of loss that may have occurred at a previous employer. So it’s absolutely vital to have a coherent hearing conservation program, which will both improve productivity and reduce absenteeism.

One way to make sure your employees are receiving adequate protection is with the 3M E-A-Rfit Dual-Ear Validation System. NRR ratings are derived from laboratory tests, so they aren’t exactly applicable to real world use unless the product is fit perfectly to maximize its effect. Many users, particularly with earplugs, don’t reap the full benefits of their product because they aren’t using it correctly. In under five seconds, the Validation System tests a user’s hearing protection against seven standard frequencies and provides extensive attenuation data, as well as a simple pass or fail rating. A fail can mean a few things: either the hearing protection is not inserted or being worn properly and should be adjusted and tested again, or the particular protection chosen is an ill fit for that particular user. Everyone’s ears are slightly different, and one size does not fit all. The system stores all results where they can be easily referred to later.

OSHA Regulations

Employers are required to provide hearing protection to workers exposed to an 8-hour time weighted average of 85 dB or higher. OSHA professionals perform audiometric tests to measure the noise levels in a given workplace, and the employer is required to keep records of the results and comply accordingly. OSHA is not a shadowy government entity looking to surveil the blue-collar workforce. They’re here to help. Consultants are available on employer’s request if you’re worried about noise conditions in your space, and there are incentives for companies that show exemplary practice in maintaining safe conditions and training employees in effective hearing protection use.

The noise level in the workplace must be monitored by the employer. Any continuous, intermittent, or impulsive noise within the range of 80-130 dB cannot be worked in without protection deemed suitable for the environment, decided by the employees and a trained specialist. If any change occurs that will affect the noise level, a new measurement must be taken and noted. Measurement instruments must be calibrated regularly per the manufacturer’s instructions. Also important are annual audiograms. An audiogram tests each individual employee’s current hearing ability and can show based on future audiograms whether a company’s hearing protection program is effective. It’s up to the employer to make sure everyone is fully informed about the reasons and structure of the hearing program, so everyone is on the same page. Organized training sessions should be held at least annually and cover four topics: the effects of noise, the differences and advantages of different hearing protectors, proper use of protectors, and the nature and procedure of audiometric testing.

Conclusion

Make no mistake, hearing protection is an urgent matter that no laborer can afford to ignore. Helen Keller once said that “blindness separates people from things; deafness separates people from people.” While hers was obviously an extreme case, the basic idea holds true. Any level of hearing damage or loss affects quality of life in a very immediate, inescapable way. All a hearing aid does is amplify sound that’s coming in, which is useless if the cochlear cilia that process the sound are destroyed. It is imperative that employers do everything they can to care for their employees’ health, and this is one of the most important and least understood areas. With a consistent hearing protection program that lets employees decide what products work best and keeps up with annual audiograms and noise level measurements, strong hearing can be maintained for a lifetime.

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