Noise Induced Hearing Loss

Prevention of Noise-Induced Hearing Loss

Despite the stringent government regulations relating to health and safety in the workplace, the incidence of industrial injury remains unacceptably high in many countries. Even though it is common enough to find notices displayed on South Africa’s mines proudly declaring that it has been 250 days or more since the last accident, not all industrial injuries are visible. In a high-risk environment such as this, one will rarely see a worker without a hard hat to protect against head injuries. Rather less obvious, however, may be the absence of earplugs that have the potential to save that worker from a lifetime of noise-induced hearing loss (NIHL).

Check out a civil construction site and those working at height will be wearing non-slip boots and be securely tethered by a safety harness. Take a quick look around most heavy engineering plants, and the various applications of the nation’s Occupational Health and Safety Act will be evident in the form of fail-safes on machines, extractors to remove harmful dust and emissions, and similar precautionary measures. However, while it is a relatively simple matter to keep a factory’s air free of harmful substances and to safeguard the digits of careless employees, there is little that can be done to limit the decibels generated in a typical manufacturing environment. Instead, employers are required to see that their workers both have and make use of a suitably effective device to protect them from noise-induced hearing loss.

Even when walking along a busy street or sitting in the garden, the average city dweller is also at risk of this type of injury. Heavy traffic, roadworks, emergency vehicles, and jet aircraft can all produce sounds in excess of 100 decibels, as can a petrol-driven lawnmower. In the kitchen, even a food blender can rack up around 90 decibels. So why are such figures significant?

In fact, it takes little more than an hour of continuous exposure to sound levels of 90 decibels, just a fraction above the average for urban daytime, to cause permanent damage to the delicate hair cells that line the cochlea in the middle ear. Secondary movements of the tiny hairs convert mechanical vibrations caused by external sounds, and conducted by the outer and middle ear, into the nerve impulses that the brain can then interpret. Once the damage is sufficient, noise-induced hearing loss becomes evident. Imagine, for example, how much greater the risk may be to a worker in an automotive manufacturing plant.

In practice, when exercising a combination of management oversight, employee self-discipline, and a sufficiently efficient protective device, such workers could actually be less at risk of impaired audition than the average shopper. Although ear defenders and earplugs are commonly issued to staff employed in excessively noisy areas, their effectiveness varies. It is equally important to the safety of an individual that, while protecting his or her ears, he or she is also able to hear co-workers clearly, without needing to remove the protection. To achieve these twin goals, a comfortable earplug moulded to the precise contours of each ear and correctly attenuated to permit the detection of speech offers workers the perfect defence against noise-induced hearing loss.

Given the tendency of individuals to cut corners when under pressure and overlook details when distracted, earplugs alone, despite their efficiency, may be insufficient protection. To ensure that such measures are as effective in the prevention of NIHL as possible, a comprehensive programme to ensure the efficient management of hearing conservation measures will ensure employers the best chance of success.

One such programme is offered in South Africa by H.A.S.S. Industrial, also the manufacturer of Noise-Ban, custom-made hearing protection. The programme begins with a needs assessment, in order to determine the prevailing levels of exposure and the most suitable form of protection to combat the risk of noise-induced hearing loss.

Thereafter, moulds are made of both the right and left ears of each worker, and from these, the finished devices with their built-in attenuators or filters are manufactured. Next, they are fitted and tested for comfort and a leak-tight fit, and the filters individually adjusted to enable safe conversation without compromising protection.

As important as the devices themselves, the programme educates staff regarding the cause and effects of NIHL, and the correct use of the earplugs. Hearing test records are maintained for each employee, and along with the condition of the earplugs, are monitored annually to ensure success in the ongoing quest to prevent noise-induced hearing loss.

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