Monday, 4 May 2015


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Noise is best defined as unwanted sound; it can be a low background sound or a loud agreeable or disagreeable sound. 

Noise is measured in decibels, running from a virtually silent 0dB(A) up to 120dB (A) or more for the very noisiest of places. For very loud short burst of sound a special scale is used to measure peak levels of noise. 

Although exposure to low or moderate levels of noise is unlikely to be very dangerous, exposure to loud noise over a prolonged period can impair hearing by damaging the fragile mechanism of the inner ear and destroying nerve cells.

Noise can cause hearing loss that can be temporary or permanent. People often experience temporary deafness after leaving a noisy place, although hearing recovers within a few hours. This is a sign that if you continue to be exposed to the noise your hearing could be permanently damaged. In some cases reduced hearing may result after only a few minutes or hours of exposure to a loud noise. In these situations normal hearing will return after a few hours away from the noise.

The effects of permanent hearing loss include speech becoming muffled so that it is harder to distinguish similar sounding words or to pick out a voice in a crowd. 

Permanent hearing damage can be caused in two ways, acute and chronic.  Acute hearing loss is caused immediately by sudden, extremely loud or explosive noise e.g. discharging a shotgun close to someone’s ear or cartridge operated machinery.  

Chronic hearing loss is caused by exposure over a gradual period of time and is sometimes referred to noise induced hearing loss, e.g. using a chainsaw over a period of time without using ear defenders. Because the hearing loss is gradual due to prolonged exposure it may only be when damaged caused by noise over the years combines with hearing loss due to ageing that people realise how deaf they have become. Hearing becomes muffled, conversations become difficult, difficulty using the phone or hearing the television.

Tinnitus is a condition that causes an intermittent or permanent ringing, buzzing or humming in the ears; this can cause severe concentration or sleep problems.

There are currently two action values set for workplace exposure to noise. The lower exposure action value is a daily or weekly personal noise exposure of 80 dB and a peak sound pressure of 135dB. At the lower action values, employers must provide their employees with information, instruction and training on the risks posed by noise and how to protect themselves. They must also provide hearing protection for employees if they ask for it and provide health surveillance if the worker is at particular risk.

The Upper exposure action value is a daily or weekly average noise exposure of 85dB (A) and a peak sound pressure of 137dB. At the upper exposure action values, employees must be provided with hearing checks and employers must ensure hearing protection is worn by employees.   

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