OHS Canada Magazine

Hear, Hear

April 17, 2019
By Jean Lian

Rising health claims due increasing hearing loss among Canada’s military personnel is a cautionary tale for industries with high noise levels. A 2016 study obtained by Radio-Canada found that the rising incidence of hearing loss is due in part to military members’ reluctance to wear protective equipment and not being provided with suitable hearing devices. Almost a third of them have chronic hearing problems by the time they retire, according to surveys by Veterans Affairs.

Like the military, industries that have high noise levels include manufacturing, construction, resource extraction, logging and entertainment establishments. According to Claudio Dente, president of Dentec Safety Specialists Inc. in Newmarket, Ontario, noise generated in the general industry ranges between 500 and 4,000 Hertz (Hz). “The human voice probably has 500 Hz; 4,000 Hz is a type of tool running at high speed,” he illustrates.

Noise-induced hearing loss (NIHL) is the gradual and irreversible loss of the ability to hear sound. There is no cure for NIHL, and noise levels in excess of 85 A-weighted decibels or dB(A) over eight hours can damage the ear. According to a WorkSafeNB document, one way to determine the need for hearing protection is if an individual can only hear when someone shouts within 0.6 metre.

On an industry level, a more scientific way to conduct noise-level tests is using a sound-level meter, which is a hand-held instrument with a microphone to measure sound that travels through air, says Bev Borst, an advanced safety specialist with 3M Canada in London, Ontario. The other method is to use a noise dosimeter, which measures the specific noise exposure of a worker by putting the dosimetry on the worker’s shoulder with a microphone near the ear to calculate noise exposure over an eight-hour average.

In most Canadian jurisdictions, the maximum permitted noise-exposure level over an eight-hour period is 85 dB(A). Quebec allows a maximum noise-exposure level of 90 dB(A), while federal workplaces put the cap at 87 dB(A). Figuring out the amount of protection needed for a work environment is the very first step, followed by selecting a hearing protector to filter down the noise below the allowed limit for the provincial requirements.

“The objective of hearing protector is not to eliminate sounds so that you can’t hear anything,” says Dente. “It is to reduce it below a dangerous level that will start to affect your hearing.”

There are two types of hearing protection: earplugs are inserted into the ear canal; and earmuffs have soft ear cushions that fit around the ear and held together by a head band.

The different types of earplugs available include foam rolldown, push to fit, reusable, banded and custom-moulded. For earmuffs, they can either be worn over the head, attached to a hard hat or has a back band. “All of them are available in communication devices too,” Borst says.

According to Borst, the attenuation or noise-reduction rating (NRR) for earplugs in general ranges from 25 to 33 decibels, while those for earmuffs hovers between 20 and 31 decibels. “What we know is workers receive about 50 per cent of NRR for earplugs.” That means for an earplug rated at 30 dB, most users will get 15 decibels of that protection. For earmuff, users get about 70 per cent of the protection, so CSA states to that the NRR on earmuffs should be derated by 30%.

One possible reason why earmuffs seem to offer a higher protection is that it is comparatively easier to put a earmuff over the head than inserting a earplug properly into the ear canal. Borst cites research indicating that about 60 to 70 per cent of users put in their plugs in correctly. That means a whopping 30 to 40 per cent of people do not get it right, which is “a fairly high percentage,” Borst suggests.

Earplugs may be a simple hearing protector, but one that people may not necessarily know how to use them properly. Part of it is lack of training and taking the time to insert earplugs properly. “I don’t think people realize how important it is to actually roll a foam earplug down, and how important it is to reach over with your opposite hand and pull the pin by holding the top of the ear, up and out,” Borst says. “If a foam earplug is inserted properly and fits, it will provide a very high level of protection.”

Dente agrees that not inserting a earplug correctly can give people a false sense of protection. Unlike a earmuff that is straightforward to don, “an earplug is a lot of work to get it in place by comparison to be effective.”

Dente recommends giving employees training or a refresher course once a year on the negative consequences of not using hearing protection properly. “People really need to be attentive to make sure they insert it properly so that it is providing an effective seal,” he adds.

When choosing hearing protectors, several key factors need to be considered. They include fit, comfort, ease of use, compatibility with other personal protective equipment (PPE), the attenuation needed and environmental factors like humidity, ambient temperature or even the need for something compact if the wearer needs to access tight or confined spaces or is wearing a welding helmet.

According to Dente, the problem with earmuffs is that it can be hot to wear for a prolonged period. Other complaints include its weight and the tight grip of the band can exert pressure on the sides of the head, causing discomfort.

If this situation occurs, a user will likely bend the wire of the earband to ease the pressure on the sides of the head, which can compromise the NRR, cautions Mino Alkhawam, product manager of DSI Safety Inc. in Laval, Quebec. As for earplugs, they can cause pressure in the ear canal. “Everyone doesn’t have the same ear canal size,” Alkhawam says. “This is why it might act differently from one person to another.”

Some earplugs have a higher expandable foam that generates more intense pressure in the ear canal, while others have lighter pressure and expands slower, hence exerting less pressure, he adds. DSI has a new hearing protector — the NP106, which is designed with a bell shape to reduce pressure inside the ear canal but continues to offer noise attenuation with an air pocket between both ends of the earplug to absorb noise and vibration.

It is important to get the right level of noise attenuation to avoid overprotecting a worker who becomes unable to hear communication, warning signals, noise from machinery and the worker’s immediate environment. “You can have possible overprotection when sound level reaching your ear is less than 70 decibels,” Borst warns. “It is important to match how much protection you are getting with the noise level, and you need to consider any existing hearing loss because they may be at a higher risk of being overprotected.”

3M carries a new electronic earplug — the EEP-100 — that provides hearing protection and improves situational awareness in challenging environments. The earpieces are small and lightweight by design, making them compatible with most head-borne PPE such as helmets and face shields. The earplug can be recharged via a micro-USB jack on the charging case, which provides easy and convenient storage of the earpieces when they are not being used. It also offers different earplug tips: reusable (available in three sizes); and a comfortable push-to-fit that does not need to be rolled down.

The other type of earpiece that 3M offers is a push-to-fit earplug. “What is nice about them is they are a foam plug, but they have a handle. So I don’t need to roll them down, and it is easy and fast to insert even for a novice user,” Borst explains.

3M™ E-A-R™ Push-Ins™ Earplugs are available corded, non-corded and in metal detectable options. The soft, flexible foam conforms to the unique shape of each ear for comfortable noise reduction. Its flexible stem requires no roll-down and makes it suited for use by people who have difficulty rolling and inserting disposable foam earplugs, such as when their hands are soiled or wear gloves.

For any PPE to be effective, users need to know the requirements of the work conditions and determine if there might be issues with compatibility. For example, a worker who already has hearing loss as a pre-existing condition should consult their physician before using any hearing protection, Alkhawam advises.

For employees who need to wear a cap-mounted hard hat, most earmuffs are designed to fit most hard hats with a sided slot. Some earplugs come with cord so that it will not fall off onto a production line, while certain earplugs are required to be visible when worn, such as those who work in the food industry. Some earmuffs come with an antenna so that a worker can listen to radio or plug into an iPod, Alkhawam explains.

One trend Dente observes is that more and more hearing protectors can be hooked into communication devices like cell phones. “The thing that is really happening in the marketplace is technology is touching these products too,” he says, citing increasing affordability as another trend.

Dentec offers Connex, a premium hearing protector with an NRR of 25 equipped with the latest Bluetooth technology. This hearing protector with a built-in microphone provides exceptional sound quality and can be connected to an iPhone or Android devices with Bluetooth and allows users to listen to music or take cellphone calls up to nine metres away from any Bluetooth device.

Proper maintenance is important to ensure that a hearing device protects as intended. “Every time you put your earplug in or muff on, you need to inspect it first,” Borst advises. “For foam plugs, make sure they are not excessively soiled or contaminated, and they return to original shape. For earmuffs, inspect for cracks or worn parts.” The outside of an earmuff can be wiped down regularly with warm water and mild soap, and it is recommended that the cushion and the inner foam be replaced every six months or earlier if they are damaged, she adds.

One thing to look out for in a earmuff is the ring inside it, typically made of polyvinyl chloride or some composite material. “We suggest people look at them every day to make sure there is no tear in seal because it will allow vibration or sound to get through if torn,” Dente cautions, adding that the sealing ring that touches the skin is clean and disinfected.

Jean Lian is editor of OHS Canada.