Ear Muffs: A Field Guide
Blocking noise is just the beginning when the latest acoustic technologies are employed.
- By Bill Sokol
- Jun 01, 2005
RECENT years have seen rapid developments in the number and types of products available to provide hearing protection as mandated by OSHA in 29 CFR 1910.95(b)(1). Not only has the design of hearing protection devices (HPDs) evolved, but the technology and materials used in their construction have advanced, as well. As a result, safety professionals are often at a loss when determining which product is best suited to their application.
These articles are intended as a brief "field guide" to recent product developments in order to ease the selection process. In part one (March 2005), we looked at ear plugs. This time, we'll check out ear muffs. Ear muffs occupy the higher end of the price scale for HPDs, ranging from $10 to $300 or more. The basic categories include passive ear muffs--which rely solely on the sound-blocking quality of the muff itself--and electronic ear muffs, including radio and communication products that utilize sophisticated electronic devices to screen out or block or modulate noise and offer additional special features as well.
Contrary to popular belief, ear muffs typically offer lower Noise Reduction Ratings (NRRs) than ear plugs. In fact, the highest-rated ear muffs on the market today have an NRR of 30 dB, as opposed to 33 for the highest-rated ear plug. This seems counterintuitive because ear muffs are bigger and heavier, but it is an ear plug's ability to fully block the ear canal that really attenuates sound. Still, ear muffs offer a high degree of comfort and usability, and most products with an acceptable NRR level will screen out block most harmful noise, most of the time, provided they are fitted and worn correctly.
Passive Ear Muffs
Passive ear muffs are made from a wide range of materials and are what most people think of as an ear muff. They block sound using just the foam and other components of the ear cup. In certain industries, such as construction, utilities, and airlines, passive ear muffs have a long history of acceptance.
When selecting a passive ear muff, there are several things to consider. Headbands can be plastic or metal. Some users feel metal is sturdier and offers the best wear, while others prefer plastic headbands because they hold their shape with more integrity. Workers often stretch out ear muff bands to make them more comfortable, but this actually decreases the level of protection the product can provide because the clamping force of the headband is one of the factors that ensuress a proper fit. Molded plastic headbands are much harder to deform because these materials have better elasticity and tend to snap right back when stretched.
Features promoting comfort and ease of use also should be considered, such as soft ear cushions, a good feel on the head, and headbands that adjust easily. Ear muffs should fit snugly and securely, creating a tight seal around the ear and not slipping around. And user instructions should be intuitive and easy to follow for a proper fit.
A number of special application styles and accessories are available for passive ear muffs. Cap-mounts designed to be fitted on hard hats are very popular in the construction, utility, and forestry sectors. Neckband ear muffs can be worn around the back of the neck so users can wear them with other safety gear such as welding helmets and faceshields; multi-position ear muffs can be worn with a band behind the head, over the head, or under the chin. These allow the ear muffs to be worn with other types of safety gear. Folding ear muffs are available for easy storage and portability with optional carrying cases, and belt clips help keep a pair of lightweight ear muffs at the ready throughout the workday.
Uniform Attenuation Ear Muffs
A fairly new product development is uniform attenuation ear muffs. These muffs not only block noise, but by employing advanced acoustic technologies design and material technologies to achieve a more uniform attenuation profile, manage incoming sound in a way that provides additional benefits. By more uniformly attenuating several key octave bands (250Hz-4KHz), protection is enhanced and incoming voice sound is less muffled and distorted. Users can hear voices and warning signals instructions more clearly and thus feel less isolated on the job.
Another promising new technology manipulates the flow of air within the ear cushion to reduce the vibration of the ear muff. This enables the muff to provide better attenuation performance in low frequencies. A typical problem with ear muffs is that they provide good protection on the high-frequency end but fairly low protection on the low-frequency end. Reducing the vibration of the ear cup provides better attenuation in the low frequencies and enhanced overall attenuation without adding weight or size to the ear cup.
Electronic Ear Muffs
Electronic ear muffs not only block sound, but also modulate that sound through electronic means. These means can be very simple, such as regulating amplifying the sound that's allowed to enter the ear through the cup, or more complex, such as offering two-way communications.
The market for electronic ear muffs is much smaller than other ear muff products, though some manufacturers are investing heavily in it. Prices can range from $60 for a basic radio ear muff product to $300 or more for high-end aviation headsets. Selection criteria are similar to passive ear muffs--comfort, fit, and durability--with the additional need to evaluate the degree of sophistication needed for the application. To block noise, most standard electronic ear muffs probably will do fine. However, if you have workers in boring or repetitive jobs, you may find job satisfaction and productivity can be improved with AM/FM radio ear muffs or products that can connect to a CD or MP3 player.
Things get more complicated when people need to talk to one another. There are a variety of products that provide these capabilities by incorporating boom microphones, two-way radios, cellphones, and the like, although not all devices have the same connectors. Customization is often required to connect these devices to the ear muff, but many users with advanced applications find this to be an acceptable solution. There are also some new, simple, and less expensive solutions to communication needs, including a "push-to-listen" capability on some electronic muffs. The key is to choose a supplier who will work with you to ensure the product is right for your application.
Providing More than NRR
A number of studies have shown that despite improvements in the effectiveness and availability of HPDs, and despite regulations mandating their use, the incidence of job-related, noise-induced hearing loss continues to rise. The reasons for this can largely be attributed to the human factor: Our species seems to have an innate reluctance to obey the rules, even when they are good for us. And because no HPD can be effective if it is not worn, safety professionals should consider these four basic rules (the Four C's) of hearing protection when selecting products for their application:
1. Comfort. If a hearing protection device is not comfortable, it will not be worn.
2. Convenience. If an HPD is not available when and where it is needed or is difficult to use, it will not be used.
3. Communication. If an HPD interferes with a user's ability to understand instructions, or if he or she feels personally isolated on the job or at risk due to an inability to hear warning signals, it will not be used.
4. Caring. If users do not appreciate the need for hearing protection, they will not wear it.
Modern hearing protection technology has come a long way in mitigating the issues related to the Four C's. Selecting HPDs with these concerns in mind will improve worker safety, improve regulatory compliance, and may very well improve productivity and worker morale, as well.
This article appears in the June 2005 issue of Occupational Health & Safety.
This article originally appeared in the June 2005 issue of Occupational Health & Safety.