Ear Protection

Why the Correct Type of Ear Protection Is So Essential

  While industrialisation and technological advances have done much to improve our lifestyles, these advances have also had their downside – one of which is the impact on public health. In addition to the negative effects of the more visible phenomenon of atmospheric pollution caused by factories and vehicles, and its role in respiratory disease, noise is proving to be an even greater threat. Not only does noise-induced hearing loss now rank as the leading form of industrial injury, but it is also responsible for the growing incidence of auditory impairment in children. Consequently, some effective form of ear protection, at least, for those required to work in noisy environments is now considered essential. To this end, many governments around the world have now included this requirement in regulations governing health and safety in the workplace.

Although the mechanism is not fully understood, repeated research findings appear to support a close correlation between NIHL and the number of functional hair cells present in the region of the cochlea known as the organ of Corti. They take their name from the hair-like projections or stereocilia that, as a result of movements of the cochlear fluid, become bent and generate differing nerve impulses which when transported by the auditory nerves, are interpreted by the brain as individual sounds, such as words or musical notes. Without suitable ear protection, sustained and repeated exposure to noise levels in excess of 85 decibels will inevitably lead to noise-induced hearing loss. In practice, the levels in a typical factory or machine shop will often be far higher than this.

In extreme cases, just a single exposure to an exceptionally loud noise, such as a bomb explosion, can cause immediate, permanent impairment. Where the explosion is milder, perhaps the result of a firework, a temporary shift in the hearing threshold may cause muffled hearing often accompanied by tinnitus, with both symptoms vanishing within a day or two.

Regardless of severity, NIHL is both permanent and currently irreversible, so ear protection, wherever the need is indicated, should be seen as an essential measure, rather than an option for those working in high-risk areas. It is therefore equally important to identify these high-risk areas. To be certain, arranging for a thorough assessment of the typical noise levels in various parts of the workplace by an experienced expert is the best starting point. Based upon his or her findings, that same expert may also be able to recommend the most effective solution.

Today, the two main forms of ear protection are the devices that resemble headphones and are known as ear defenders, and earplugs. In terms of their relative ability to block the passage of sound, the former, more sophisticated looking structures actually tend to be less effective than their apparently simpler rivals. One obvious explanation for this is that while the defenders rest over the entrance to the auditory canal, earplugs fit into the canal entrance itself. Rather like covering your ears with your hands compared with sticking your fingers in them, earplugs are able to exclude sound more effectively.

To provide effective ear protection in the workplace, it is not enough to preclude all sound indiscriminately, as to do so would render essential conversation with supervisors and between co-workers impossible. This means that, for such purposes, the use of tightly-fitting, conventional earplugs would be of little value, since it would be necessary to remove them when talking with others, which would then re-expose the wearer to the risk of NIHL.

Nevertheless, when designed with care, earplugs can definitely provide workers with the most efficient form of ear protection currently available. When it comes to design, the first requirement is a perfect fit: not just tight, but individually moulded, so as to match the unique contours of the proposed wearer’s left and right ears exactly. Thus, casts from which to fashion each plug must first be taken and, once fitted, each plug will need to be tested for any possible leaks. The remaining requirement is for a means to permit conversation without compromising the protective function of the earplugs. Without this facility there is a real risk that workers will simply avoid wearing them. To gain acceptance, earplugs must preserve the audibility of sounds of low to moderate intensity, only attenuating those of high intensity. Technology allowing attenuation levels to be adjusted to a given working environment is a key factor in providing safe and practical ear protection.