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Workplace health and safety

Home > Workplace health and safety > Law and penalties > Noise Code of Practice 2004 > 1. What is noise?

1. What is noise?

1.1 What is excessive noise?
1.2 How is a person’s hearing damaged?
1.3 What are the effects of noise exposure?

Noise is unwanted sound1 that may damage a person’s hearing. Noise or sound consists of relatively small changes in atmospheric pressure. The changes are detected by the eardrum and carried to hair cells in the inner ear. These hair cells convert the pressure changes to electrical pulses which are sent to the brain. The brain is then able to process these electrical pulses into meaningful sounds.

The amount of damage caused by noise depends on the total amount of energy received over time. This means as noise becomes louder it causes damage in less time.

Sound pressure level2 is measured in decibels (dB). The decibel scale is logarithmic, or compressed, as the human ear is capable of hearing a broad range of sound pressures.3

For every unit change in sound pressure there is a greater than unit decibel change. For example:

How the ear works

1.1 What is excessive noise?

Excessive noise is defined in the Workplace Health and Safety Regulation 1997 and means a level of noise above:

For the complete noise regulations please see appendix 1.

What does LAeq,8h of 85 dB(A) mean?

LAeq,8h of 85 dB(A) means the actual energy of varying noise levels experienced over a working period is equivalent to 8 hours of a continuous steady A-weighted sound pressure level of 85 dB(A).

In simple terms, this can be shown in the following graph which has a range of time/sound level variations equivalent to a daily noise exposure8 level. For example, a person exposed to a continuous sound pressure level of 94dB(A) over a period of 1 hour has experienced the same noise exposure as a person that is exposed to a continuous sound pressure level of 85 dB(A) over 8 hours. The graph demonstrates the allowable noise exposure, in hours per day for various sound levels.

Scientific evidence indicates that continuous exposure levels above 85 decibels, during a normal 8 hour working day, represent an unacceptable risk to the hearing of those exposed.

Daily noise exposure levels

What does LC,peak of 140 dB mean?

LC, peak of 140 dB(C) means a C-weighted peak sound pressure level of 140 dB(C). Levels of noise above LC,peak of 140 dB(C) can cause immediate hearing damage. This is often referred to as ‘acoustic trauma’ and can result from an event that causes very loud noise, for example, an explosion or drop forcing.

1.2 How is a person’s hearing damaged?

A person’s hearing ability can become temporarily or permanently impaired if the person’s unprotected ear is exposed to excessive noise.

Temporary hearing impairment is known as temporary threshold shift and may be experienced as dull hearing. It may also cause ringing in the ears after noise exposure. Recovery from temporary threshold shift may take from a few seconds to several days or weeks, depending on the severity of the noise exposure.

However, in many cases ‘normal’ hearing returns overnight giving the false impression that the person has fully recovered. A person who experiences temporary threshold shift repeatedly can suffer permanent hearing damage if noise exposure continues.

The severity of noise induced permanent threshold shift will vary with the characteristics of the noise. The level, duration and pattern of noise exposure and a person’s own susceptibility to hearing impairment determine the severity of damage.

Hearing damage of this type is often accompanied by a permanent ringing, buzzing or roaring sounds in the ears, which is known as tinnitus.

1.3 What are the effects of noise exposure?

Exposure to excessive noise

Noise at the workplace is a major cause of deafness in Queensland. Not only does workplace noise cause deafness, it can also contribute to increased absenteeism and worker turnover, as well as lowered work performance. It can also contribute to workplace injuries and accidents.

Occupational noise induced hearing loss is a major compensable industrial disease in Australia and entails substantial economic and social costs.

A person working with or near noisy machinery or equipment may be affected by high direct or ambient noise9 and may develop noise-induced hearing loss (NIHL) as a result of working under those conditions. Both temporary threshold shift and permanent hearing damage can affect a person’s social and work life.

Some of the effects of noise-induced hearing loss10 include:

Other effects are:

Permanent and severe tinnitus may disrupt sleep, reduce concentration and lead to irritability or depression. Vibration effects from exposure to excessive noise can also affect a person’s sight, for example, loss of clarity, colour perception and night vision.

Permanent NIHL cannot be reversed or cured. People suffering from NIHL often have communication and personal relationship problems. They also experience social isolation and degradation of the quality of life. Family and friends are often also affected and experience the secondary effects of the condition.

Hearing aids may be of some benefit in overcoming some of the problems but normal hearing can never be fully restored. Twenty percent of people affected by NIHL also suffer from tinnitus, or ringing in the ears. Severe tinnitus can be experienced by the sufferer 100% of the time.

Exposure to low level noise

Relatively low noise levels, like those in offices, typically range between LAeq,8h 40 and 75 dB(A). These noise levels depend on the interior construction of the workplace and the activities carried out. Under these conditions, low noise levels are not capable of causing NIHL. However, they are known to cause stress and other adverse health effects in some cases.

People may experience stress in different ways. For example, stress can take the form of fatigue, anxiety, depression, hostility or aggression.

Noise may lead to:

Stress related symptoms include:

The body will try to cope with a situation of intrusive background noise by adapting its biological functions. These adjustments are made by increasing the heart rate and raising the blood pressure. Also, more hormones like adrenaline and cortisol are released into the body.

Under stressful working conditions, prolonged high levels of these hormones may lead to more serious health effects.

Health effects may consist of:

Exposure to both excessive or low levels of noise can result in:

These results can be avoided if an employer or other obligation holder takes steps to manage the risks from exposure to noise at the workplace.

1 'sound' means small fluctuations in the air pressure that result in a wave capable of exciting in a listener the sensation of hearing.

2 'sound pressure level (SPL)' means the relative magnitude of sound pressure, customarily expressed in decibels referenced to 20 micropascals.

3 'sound pressure' means the alternating component of the pressure at a point in a sound field.

4 'A-weighted' means a standardised frequency response (in dB(A)) used in sound measuring instruments and corresponding approximately to the human ear response.

5 'dB(A)' means A-weighted decibels.

6 'C-weighted' means a standardised frequency response (in dB(C)) used in sound measuring instruments and corresponding approximately to the human ear response.

7 'dB(C)' means C-weighted decibels.

8 'noise exposure' means the amount of sound energy the unprotected ear of a person is exposed to, given as LAeq,8h or as LC,peak.

9 'ambient noise' means the all-encompassing noise associated with an environment, being a composite of sounds from many sources near and far.

10 'noise-induced hearing loss' means hearing impairment arising from exposure to excessive noise at work. Occupational noise-induced hearing loss is also commonly known as industrial deafness.

Last updated 28 August 2008