Most Cases of Hearing Loss are Now Noise Induced

Over the years, noise pollution has been the subject of much attention and has seen strict regulations enforced in many areas, in attempts to reduce it to more tolerable levels. Much of the legislation was directed at airports and based upon complaints of the intrusive effect on lifestyles, disturbed sleep and the negative consequences for property values in nearby residential areas. By contrast, similar legislation introduced in the nation’s places of work was directed, instead, at the potential impact of excessive decibels on the health of employees and on the high incidence of noise-induced hearing loss (NIHL) experienced by workers in many industrial environments.

A study of the latter, led to the introduction of new health and safety measures requiring employers to provide protection against the risk of NIHL – minimising ambient noise levels wherever possible and providing ear defenders for employees. To better understand the risks of exposure, it is first necessary to understand how the ear functions and how repeated and over-stimulation can, quite rapidly, lead to varying degrees of permanent deafness.

Upon reaching the outer ear, sounds are funnelled to the tympanic membrane or eardrum, which vibrates in response. These vibrations, in turn, agitate the first of a trio of tiny bones in the middle ear that, together, act to conduct the kinetic energy to the inner ear where it agitates the fluid present in the cochlea. A section of this organ, known as the organ of Corti, is lined with specialised cells from which hair-like, sensory structures protrude. When agitated by fluid movements, they generate nerve impulses that are relayed to the auditory centres in the brain where they are interpreted as speech, musical notes etc. In noise-induced hearing loss, repeated and prolonged exposure to high volume sounds damages the hair cells which, in human subjects, the body is unable to regenerate.

It is easy to see, therefore, how a worker who may be required to operate heavy machinery, such as a pneumatic drill or milling machine, for many hours at a time or to work in close proximity to a jet aircraft on a daily basis might well become affected, unless he or she is taking adequate precautions. However, times and circumstances have changed, and it is no longer such personnel alone who are exposed to the risk of developing NIHL.

In general, even with prolonged exposure, sounds at levels below 75 decibels are most unlikely to prove damaging. So, while the humming of a refrigerator may be annoying, at a mere 45 decibels, it should never impact your ability to hear. On the other hand, heavy city traffic can typically generate around 85 decibels, so when faced with a long commute, it’s best to keep the windows closed and to live with the 50 or so decibels generated by your air con.

Statistical studies confirm that noise-induced deafness is growing alarmingly among the younger generation, with children as young as ten years being afflicted by varying degrees of permanent deafness. One does not need to look too far for an explanation, however. MP3 players are typically enjoyed at full volume and can generate an ear-splitting 105dB. If your child is at risk of NIHL, don’t hesitate to seek professional support from your nearest Ear Institute centre.

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