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Noise-induced Hearing Loss

How Likely Are You to Develop Noise-Induced Hearing Loss?

It is not uncommon to experience some degree of auditory impairment as you age. Known as presbycusis, auditory acuity begins to lessen towards the end of the third decade and continues to decline slowly, often without any noticeable difficulties until quite late in life. Some individuals may be born deaf and others become so as a result of ear infections, certain illnesses, or injury. While such incidences are essentially unavoidable, the most common form of hearing loss encountered today is noise-induced and preventable with just a few simple precautions.

Commonly abbreviated to NIHL, it was first observed in members of the armed forces returning from the First World War. However, only after the second world conflict, with the development of audiology, was it possible to investigate the condition further. From those studies, came the realisation that NIHL was not confined to those exposed to gunfire and explosions. In practice, the condition has long been a problem among mine workers in South Africa and, until quite recently, most of the local research into NIHL has been focused on the mining industry. The intense noise resulting from the use of pneumatic drills in confined spaces was found to have resulted in noise-induced hearing loss in 40-80% of those involved in drilling operations, after ten years of constant exposure. The findings led, in 1988, to the publication of guidelines for hearing conservation by the Chamber of Mines.  

Over time, it has become all too apparent that many more employees in a far wider range of industries are also at risk of NIHL. Accordingly, regulations designed to protect them are now in place, and defined by the Occupational Health and Safety Act (OHSA) of 1994. That the condition is widespread seems clear, but how is it possible for loud noise to induce hearing loss?  

Lining a section of the cochlea in the inner ear, there are some specialised cells that are characterised by delicate, hair-like projections or stereocilia. These tiny hairs are responsible for converting mechanical disturbances in the cochlear fluid, resulting from incoming sounds, into nerve impulses which are then transmitted by the auditory nerve to the auditory cortices in the brain for interpretation. While birds and amphibians have the ability to regenerate these hair cells, should they become damaged, humans are unable to do so. A loud gunshot or explosion can cause instant damage to the hair cells, but most often, noise-induced hearing loss occurs as a result of the cumulative damage caused by repeated and prolonged exposure to sounds above the safety threshold which is generally recognised as being 85 decibels.  

At this threshold level, and depending upon how close you may be to the source, eight hours of continuous exposure can be enough to cause permanent impairment and each further exposure will compound the extent of the damage. This is a fact that prompts an important question. Is it possible that you are at risk of developing noise-induced hearing loss?   In practice, although the risk is definitely greater among those who are required to work in a noisy environment, we are all at risk to some degree. Since the invention of the internal combustion engine and electrical power, modern living has become progressively noisier. Where once the only disturbances might have been the rustle of leaves at around 20 dB, a running stream at approximately 40 dB, or conversation and laughter at levels somewhere between 50 and 65 dB, our senses are now assailed by the sounds of jumbo jets and jackhammers as we navigate the busy city streets.  

Those who enjoy music are also at risk of noise-induced hearing loss. A symphony orchestra can generate 110 dB, while a rock band can churn out up to 140 dB, so be sure not to sit too close to the front or to a loudspeaker. Portable music players, such as iPods and smart phones, are a particular threat to young people who tend to play them at full volume. Because the decibel scale is logarithmic, this could be more than a hundred times more intense than the safety threshold.  

So, how can you minimise your risk of noise-induced hearing loss? In excessively noisy situations, some form of hearing protection is essential. Contact us to find out more about our Noise-Ban products and how they can lower your risk of developing noise-induced hearing loss.

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