Earmuffs provide consistent and quality protection against noise exposure
|Brad Witt, MA|
In the defense against hazardous noise exposures, earmuffs are a valuable weapon in the hearing protection arsenal. Earmuffs offer some advantages not available in earplugs and other hearing protection devices, appealing to both occupational and non-occupational users.
One of the biggest misconceptions about earmuffs relates to attenuation. Assuming “bigger must be better,” many novice users mistakenly think that earmuffs block more noise than earplugs. But this is not the case; as a group, earmuffs generally have lower (but more consistent and repeatable) attenuation than most properly-fit earplugs. When it comes to higher attenuation, it is more efficient to seal an ear canal with an earplug than it is to seal a pinna with an earmuff.
So why would a user choose an earmuff over an earplug? The best advantage is the ease in obtaining a proper fit. If users properly adjust the headband and avoid obstructions like thick hair or thick eyeglass frames, there is a high probability they will achieve hearing protection relatively close to the rated attenuation. The same cannot be said for earplugs – many things can go wrong in a typical earplug fitting, and the difficulty in obtaining a proper deep insertion prevents most earplug users from achieving optimal attenuation.
Other advantages of earmuffs include their convenience for intermittent noise exposures (they can easily be left around the neck when not in use), newer electronic options, and even added warmth for the ears in cold environs. Earmuffs can be fit over hearing aids for those workers who prefer using their aids on the job. Even if earplugs are the predominant hearing protector in a noisy worksite, it is advisable to keep earmuffs as an option for workers who may be temporarily unable to use the earplugs due to ear infections.
The disadvantages of earmuffs? Many users feel they are hot and heavy for extended use, especially in warm or humid environments. Additionally, care must also be taken to ensure the earmuffs are compatible with other personal protective equipment (eg, hardhats, eyewear).
Earmuffs can generally be divided into two groups: 1) passive earmuffs which rely solely upon the sound-blocking quality of the earcup and its foam insert, and 2) electronic earmuffs which use internal circuits to amplify or attenuate certain sounds, or add other specialized features to the earmuff. Passive earmuffs are the most common choice in industry, ranging in attenuation from about 20-30 dB. They are available in a number of styles for special applications: cap-mounted versions for use with hardhats and multiposition styles that allow the earmuff to be worn simultaneously with welding helmets and faceshields, or folding models that can be easily stowed or carried. They are also offered in high-visibility colors for road crews, airports, etc, where visibility is critical.
Electronic earmuffs have the same protective benefits of passive earmuffs, and come in a variety of styles (cap-mounted, high-visibility, etc). They also offer an impressive array of options for specialized applications, though at an added cost. Their labeled attenuation is always measured in the passive mode (electronics turned off). But their best features shine when the electronics are turned on.
Amplification is one of the simpler features found in electronic earmuffs. Microphones mounted on the earcups feed the signal to an amplifying circuit which has a built-in limiter. Either by compression or peak-clipping, the speaker driver is controlled such that maximum output does not exceed 82 dB—still a safe level for occupational noise exposures. Worn at a construction site, for example, the user would clearly hear warning signals and co-workers, but also be protected from intermittent hazardous noise emitted by power tools or impact sounds. Some amplification earmuffs can be plugged into cell phones and MP3 players. And one variation of the amplification earmuff is the AM/FM radio earmuff, offering entertainment while still protecting from hazardous noise.
At the high end of specialty earmuffs are communication headsets and Active Noise Reduction (ANR) earmuffs. Communication headsets have moved from traditional hardwire connections to wireless systems utilizing FM or Bluetooth technology. Earmuffs can be configured for listen-only or two-way communication. ANR utilizes phase-reversing circuitry to effectively cancel much of the incoming sound energy. It is most effective in low-frequency continuous noise, but the cost has deterred widespread usage in occupational noise exposures. But ANR headsets have found broad acceptance among commuters and pilots, for whom the noise reduction is most effective.
FAQs About Earmuffs
Do earmuffs require any maintenance or care? Durable earmuffs can withstand years of regular usage, but there are a few key care instructions. Clean ear cushions and headband regularly with mild soap and water. Damaged cushions can impact attenuation, and the cushions and foam inserts should be replaced every 6-12 months with normal wear.
Can earmuffs be worn over eyeglass frames? The attenuation of an earmuff obviously depends upon a tight seal between the ear cushion and the head. For eyewear with a thin frame (a width of 2 mm or less at the temples where the earmuff cushion meets the frame), eyewear usually causes no significant decline in attenuation. However, eyewear with thick frames (6 mm or more, often seen on safety glasses with adjustable-length temple bars) can create a gap which causes a loss of 9-12 dB of attenuation in the low and high frequencies.
What about dual protection (earmuffs worn over earmuffs)? Using earplugs and earmuffs concurrently seriously isolates the wearer, so it is warranted only in extreme noise levels. The amount of attenuation achieved from dual protection is not simply the combined ratings of the earplug and earmuff. There is a ceiling effect that limits combined protection. One study shows that an earmuff typically adds about 4 dB to the NRR of a well-fitted foam earplug, and about 7 dB to a well-fitted pre-molded earplug. It is not necessary to use the highest-rated earmuff to achieve maximum attenuation from dual protection; an earmuff with moderate attenuation, for example, has about the same effect as a high-attenuation earmuff when worn over a well-fitted earplug. The key to obtaining maximum benefit from dual protection is proper fit, especially the fit of the earplug. When a poorly-fitted earplug is worn with an earmuff, the resulting dual protection is little more than the earmuff alone.
Is it safe to use an AM/FM radio earmuff in hazardous noise? A wary safety manager might question how a noise-exposed worker can safely wear a radio earmuff in loud noise. But, like the electronic earmuffs described above, radio earmuffs have built-in circuitry to limit the output of the speaker and cannot exceed 82 dB. This means the radio earmuff can be safely used in ambient noise exposures of 100 dB. The combined level of the occluded ambient noise and the radio output is still safely in the low-80 dB range. Radio earmuffs are not for every job title—certainly not for workers near moving heavy equipment, or jobs that require concentrated focus. But for tedious or monotonous jobs, one study finds that 79% of workers felt their productivity increased by listening to music on the job.
Can a worker use hearing aids under earmuffs? Many hearing aid users prefer to keep using their aids at their noisy workplace so they can still hear co-workers, warning signals, and machinery noises. Hearing aids alone do not provide adequate attenuation to be used as hearing protectors. So users often fit an earmuff over their hearing aids to combine protection and amplification. Two earmuff styles that are particularly well-suited for use with hearing aids are flat attenuation earmuffs (which attenuate frequencies fairly uniformly with less distortion to incoming sound) and amplification earmuffs. By adjusting the volume setting of the hearing aid and the amplification earmuff, many hearing aid users achieve a workable balance between sound amplification and noise protection. Amplification earmuffs are also an excellent option for workers with some existing hearing loss who do not wear hearing aids.
Brad Witt, MA, is audiology manager at Howard Leight Industries, San Diego, part of the Bacou-Dalloz Hearing Safety Group, where he manages the Acoustical Laboratory and provides training to professional groups. He is past president of the National Hearing Conservation Association (NHCA) and managed a hearing conservation practice for 14 years.
Correspondence can be addressed to Brad Witt, Howard Leight Industries, LLC, 7828 Waterville Rd, San Diego, CA 92154; e-mail: .