Noise induced hearing loss

Our senses are based on an ability to capture incoming information and translate those triggers into meaningful information. And so, hearing is based on an ability to capture sound waves coming into the ear from the surrounding air that are then delivered via the hearing nerve to the brain. Any form of hearing loss will impair this ability to capture and/or deliver incoming sound.

In the western world, the two most common types of hearing loss are age-related and noise induced hearing loss. Age-related hearing loss is a gradual deterioration in hearing ability due to deterioration from the natural aging process, which can start from as early as a person’s 40s and is not preventable. On the other hand, noise induced hearing loss (NIHL) is an external cause and can be prevented.

How Our Hearing Works:

The ear can be divided into three parts, all of which work together to achieve the sophisticated process of hearing. The three parts are the outer, middle and inner ear sections.

The outer part of the ear, the pinna helps to direct sound waves down into the ear canal. When sound waves reach the end of the ear canal, it causes the eardrum to vibrate and in turn passes these vibrations through three tiny bones of the ossicular chain in the middle ear. These three bones (malleus, incus and stapes) form a bridge to transfer the energy of the sound waves from the outer section of the ear through to the fluid section of the inner ear. A critical part of the inner ear is the cochlea which houses thousands of tiny ‘hair cells,’ responsible for sending signals via the hearing nerve fibres to the brain to interpret.

When Does NIHL Occur:

Prolonged exposure to harmful noise may cause damage to the tiny hair cells within the cochlea, putting our ability to hear at risk. Furthermore, as the body is unable to regenerate hair cells, noise induced hearing loss, (and any hearing loss caused in this way) is irreversible which means that any ‘cure’ is merely a way to manage the condition. The degree of resultant hearing loss caused by noise induction will depend on factors such as: how long the exposure lasted for and how loud the noise was. Therefore the level of hearing loss will vary from one person to the next. It is never too late to try to reduce the amount of noise we are exposing our ears to.

How To Reduce NIHL:

It is usually a number of steps that must be taken to reduce the risks of hearing loss from exposure to loud noise rather than a ‘one fits all solution’. These steps can include:

Identifying the problematic areas – the job of the person in charge of health and safety is to identify areas that exceed the permitted level of noise.

Moving to quieter processes – The best means to avoid the possibility of hearing loss is to try to deal with the source of the noise; moving to quieter machinery should be investigated.

Using hearing protection – Noise prevention in the form of earmuffs and earplugs are extremely useful, however one must bear in mind that even the best carry an upper limit in terms of how much decibel reduction these offer. For example, a good quality earplug that fits the wearer well may carry a noise reduction of up to 20dB. If a noise assessment measured 110dB in the area and guidelines do not permit noise levels to exceed 80dB this solution alone would be ineffective. While it is possible to combine two types of hearing protection (e.g. plugs and ear muffs) to increase their dB reduction employees should never be completely isolated from sound around them. Such isolation carries its own set of risks.

Set procedures – Policy should be in place to endorse the combination of steps taken to reduce the risks of hearing loss. Clear guidelines must be made given as to when and how hearing protection should be used. Employees should also be given access to have regular hearing tests.

Article written Joan McKechnie BSc Hons Audiology & Speech Pathology. Joan works for Hearing Direct, which offers a range of hearing equipment for the deaf and as well as hearing protection aids.