Every day, people damage their hearing. Whether listening to music that is turned up too loud, the noises from a job site, or damage caused by head trauma or medical conditions such ear infections, the ears are subject many kinds injury. Working in loud noises is the most common cause of hearing loss. It is for this reason that we need to look at the causes of hearing loss and what is needed for hearing protection.
Continuous vs. Intermittent Noise
When determining the type of noise and the decibel level at your worksite, you need to determine whether the noise level is continuous or intermittent. Continuous noise is noise that remains steady for a given period of time. Examples of this would be boilers or engines on ships. Intermittent or variable noises are noises that cause sound changes over time. This usually means periods of relative quiet and loud noises. Manufacturing facilities and construction sites have intermittent noises. On a construction site, the use of a chop saw would create a variable noise. A third type of noise is impulse or impact, which is a noise that lasts less than one second. A punch press creates an impact noise.
Decibels are the unit used to measure sound. The American Conference of Governmental Industrial Hygienists in their threshold limit values publication has stated the maximum amount of noise that a person can be exposed to before damage starts to set in. For an eight hour period, the maximum noise allowed is 85dB, which would be a diesel truck from 50 feet away or the average factory or for a twelve hour day 82Db, about the volume of a dial tone. The maximum exposure for fifteen minutes is 100dB, which is the level of noise for a lawn mower or a jackhammer. Maximum exposure for fifteen seconds is 118dB, which is the equivalent noise for a chain saw or oxygen torch. With these numbers, you can see why hearing protection would be required on jobsites.
Requirements for Protection
The Canadian standard for hearing protection is CSA Z94.2-14. Among the requirements that it lists is that all hearing protection is to be made of materials that can be cleaned according to the manufacturer’s specification and will be non-irritating to the skin, unless it is only meant for one use. All devices are to be part of a hearing loss prevention program that will contain at least the following elements:
- Noise exposure assessment of all people potentially exposed to noise levels in excess of 85dB (or as required by the authority of the jurisdiction) in their place of work
- Control of the noise exposure through the control of the noise source, the noise path, or the individual’s exposure
- Selection of adequate hearing protection for all noise-exposed individuals taking into account factors such as noise exposure, comfort and overprotection
- Training of all users in the fit, care, and the use of the protectors provided
- Posting of noise hazard areas
- Audiometric testing
Earplugs vs. Earmuffs vs. Helmets
The most common type of protection device is earplugs. Earplugs are placed in or against the entrance of the ear canal and form a seal to block sound. There are seven different types recognized by CSA. The first is the foam earplug, which are sometimes referred to as disposable or roll down earplugs. These are rolled before inserting into the ear canal to fit properly. Push-to-fit plugs have a pod or dome at the end of a flexible stem, and have a longer life than roll downs.
Pre-moulded earplugs are made from flexible materials and formed into conical, bulbous or other shapes with a flange or sealing ring. They can be one-size fits all or in a range of sizes. They are pushed into the ear canal. Formable earplugs are not meant for industry, since they are only made from silicone putty or a cotton wax combination.
Custom moulded earplugs are only meant for the wearer who they were fitted for, using ear canal impressions. While these are more expensive, they also tend to last, longer than other types of plugs, typically three to five years. The impression itself becomes the plug and should it need to be replaced, the moulding process has to be repeated.
Earmuffs are moulded plastic ear cups that seal around the ear using foam, fluid of gel filled cushions and are held in place by a metal or plastic band that keeps the cups secure and tight to the wearers head. Acoustic absorbing material is used inside the cup to reduce sound.
Helmets enclose the head and are primarily meant to provide impact protection. Their hearing protection is more for recreational settings, such as a motorcycle, or the military.
When selecting the type of hearing protection device you need, you need to remember the classes and base it on the noise level that exists in the workplace. If the noise level is less than 85 dBA there is no need for hearing protection. If the noise level is between 85 to 89 dBA than you will need Grade 1 or Class C. Noise at 90 to 95 dBA requires Grade 2 or Class B. A noise range of 95 to 100 dBA will require Grade 3 or Class A. Finally, a daily noise exposure between 100 and 105 requires Grade 4 or Class A.
After identifying the class you require, there are other factors that you can consider. Comfort, especially if being worn for long periods of time, price, and the level of protection should be considered. Ear plugs are easy to use, cheaper and more comfortable in hot, damp environments; they do not offer as much protection though, they take time to fit, they may irritate the ear canal and are easy to lose. Ear muffs will fit to almost everyone, easy to see when monitoring use, not easily misplace, and can be worn with ear infection. The disadvantages of ear plugs are they are heavier, can be inconvenient to wear with other PPE (although there are some types that can attach to hard hats), and they are uncomfortable in hot weather.
By having a program as required by CSA, workers can retain their hearing. Statistics Canada estimates that the cost of hearing loss on the Canadian economy is $10.6 billion. Hearing loss is preventable, and by selecting the right hearing protection device and training in the care and fit, workers can avoid this debilitating affliction. My grandfather ran a sawmill for years and by the time he retired, he had lost most of his hearing. He had difficulty hearing and trying to function. So why would you want to endure this? Plan to stay safe.