Safety & Compliance
Noise
Noise is one of the most widespread hazards facing Australian workers. It is rare to enter a workplace and not be assaulted by the din of metal crashing against metal, the roar of vehicle movements, the shrill blast of compressed air being released, or the rumbling of engines and compressors. All of this noise is unnecessary in that it could be designed out of the machinery. All of it is hazardous in that it leads to deafness and increases the risk of accidents and other health effects.
Now consider the health effects from being subjected to excessive noise in the workplace.
Effects on Hearing:
In the short term, fatigue of the hair cells in the cochlea leads to short-term hearing loss, or temporary threshold shift. It may last for a few minutes, hours or days after starting on a noisy job, and is essentially a reversible adaption of the hair cells to an unwanted excess of sound energy.
In the longer term, permanent noise-induced hearing loss, or deafness, is produced if exposure continues to noise of high intensity. The hair cells of the inner ear are eventually killed by such high-intensity noise, which is why resulting hearing loss is permanent and irreversible.
Noise not only damages hearing sensitivity but can also give rise to tinnitus, a disturbing ringing in the ear. This usually persists and is especially worrisome at night when it can prevent getting to sleep. In people with normal hearing it is rarely heard, but as deafness sets in the echo becomes tormenting.
With advancing years the auditory sensitivities diminish, particularly in the higher frequency end of the spectrum (4000 to 6000 Hz). This occurs irrespective of whether a person has been exposed to noise.
Very loud, impact noises from explosions cause a special form of damage termed acoustic trauma. The burst of energy accompanying impulse noise can not kill the hair cells of the inner ear, but can damage the eardrum and ossicles. The eardrum can generally repair itself over time, but the hair cells can not.
Noise-Induced Stress:
Noise acts on the body as stress, arousing us through a series of bodily reactions. Basically, the response involves putting the body into a state of shock, chiefly through release of the hormones cortisol and adrenalin.
Noise-induced stress leads to irritability, tiredness and headaches which may increase blood pressure, strain the heart and affect vision.
Noise as a Safety Hazard:
Noise interferes with communication between workers. This can create safety hazards when one worker cannot warn another of danger. In addition, not being able to speak to each other deprives workers of the normal personal relationships that all people need.
Noise as a Source of Annoyance:
Quite apart from fatigue, noise at work can cause annoyance. For example, noise levels in offices would rarely reach levels likely to cause hearing damage, yet the noise of keyboards, telephones, music and people may be sufficient to interfere with concentration.
Control Of Noise:
The options available for controlling the sources and reducing the noise levels at the worker's ear are threefold:
Control at the Source - means reducing the noise output of machines and should be the first line of defence.
Control of the Noise Path - means placing shields and baffles between the noise source and the operators, and is the second line of defence.
Enclosure of the operator - when the operator is enclosed in a soundproof booth.
Personal Protective Equipment:
Only when all the above alternatives have been investigated and assessed as unachieveable will this option be adopted. It also limits their ability to discuss mutual work problems, and may even be considered a barrier to concerted activities, which are a right of all workers. Finally, since some speech communication is necessary even in noisy shops, many workers in noisy industries develop throat disorders and voice problems from having to shout to one another to be heard.
In Tasmania the Workplace Health and Safety Regulations 1998 set exposure to noise in the occupational environment to levels which must not be exceeded. These levels are an eight-hour equivalent continuous A-weighted sound pressure level, LAeq,8h, of 85dB(A) or a peak noise level, Lc,peak of 140dB(C).
The National Standard for Occupational Noise should be referred to for advice. Attached to this Standard, which is available from the Australian Government Publication Information Service , is the National Code of Practice for Noise Management and Protection of Hearing at Work [NOHSC] which provides useful information in addressing particular workplace problems.
