An introduction to noise at work

This page answers some of the most frequently asked questions relating to noise.

How can noise affect your life?

Hearing loss caused by noise is insidious and permanent. It can cause isolation at home and socially and decrease efficiency at work.

High pitched sounds, such as consonants and women's and children's voices, are the most affected by noise-induced hearing loss. Thus, while some sounds are still loud, others are filtered out and speech can't be understood. With more than one person speaking or a background noise, the problem is worse. 

Unfortunately, lost hearing is gone forever. Hearing aids offer only limited help in decoding the distorted message. 

Ringing or other noises in the ears or head, known technically as tinnitus, can also be caused by excessive noise. It too can become permanent in some people and when severe may disrupt sleep, reduce concentration, make you extremely irritable and lead to depression.

Are you at risk?

If the noise around you makes it necessary for you to raise your voice to make yourself heard to somebody one metre away, your hearing is probably at risk. 

Remember, although it may seem that your ears become 'used to' noise, this is in fact due to temporary hearing loss. 

Repeated exposure to excessive noise will eventually lead to permanent damage.

Noise does not have to be painful to be doing damage.

Why sound?

You need sound to communicate with people and experience the environment around you. Too much sound damages your hearing, leaving you isolated from society. It may also cause you stress and fatigue and reduce your efficiency at work. Not only unwanted noise, but also loud sounds that you enjoy may harm you.

How do you hear?

Sound travels through the air in pressure waves. Your ear detects the pressure changes and sends messages to your brain. Your ear is very versatile and sensitive - it can detect and respond to tiny noises such as a ticking clock and noises 1,000,000 times as loud, such as a jet engine. However, loud noises damage the delicate mechanism.

How does too much noise damage your inner ear?

Sound stimulates tiny hair-like cells in your inner ear which send messages to your brain. Like wind blowing in a tree - a little is alright - between puffs of wind the tree springs back into an upright position. However if the wind blows too hard or for too long the tree will become permanently bent and may break. Similarly, the hair-like cells are damaged by too much noise for too long. While at first, given enough quiet, the cells may recover, repeated noise will lead to permanent damage. Often damage occurs gradually over a number of years and remains unnoticed until it is too late. The damaged cells can no longer send the messages to the brain and hearing is lost. 

Extremely loud noises can cause immediate lasting damage. The sudden burst of energy in noises such as hammering or gunshots can cause this type of damage.
A number of common workplace chemicals can also cause hearing loss themselves or exacerbate the effects of noise.  These are called ototoxic chemicals.

How much noise?

The loudness of the noise depends on the size of the sound pressure wave - the bigger the wave, the louder the noise.

However, while loudness expresses our general response to a noise, our ears do not always accurately assess the damage that it can do. For this, we measure the energy content of the noise and express it in terms of a level in decibels (dB).  

Because of the large range in noise levels that can be detected by the ear, the decibel scale is not a normal scale. Instead, a 3 dB increase in noise level, though barely perceptible, corresponds to a doubling of sound energy. A 10 dB increase, indicating 10 times the energy, seems twice as loud.

Because of the large range in noise levels that can be detected by the ear, the decibel scale is not a normal scale. Instead, a 3 dB increase in noise level, though barely perceptible, corresponds to a doubling of sound energy. A 10 dB increase, indicating 10 times the energy, seems twice as loud.

Measuring noise level

Noise levels are usually measured using a sound level meter. The meter responds to the pressure changes of the noise producing a sound pressure level. When the noise level varies, an integrating sound level meter will provide the average.

Noise exposure - the Equal Energy principal

The amount of damage caused by noise depends on the total amount of energy received over a period of time, the louder the noise the faster it causes damage. A noise 3 dB greater has twice the energy output and causes the same damage in half the time.

Measuring noise exposure

Personal daily noise exposures can be measured by small noise exposure meters (also called dosemeters) carried on the person throughout the day. Alternatively, exposures can be estimated using individual noise levels and duration times for tasks done throughout the day.  A Ready Reckoner​ can be used to assist with this calculation.

The frequency phenomenon

The way a noise sounds depends on the pattern of frequencies or pitches it contains. Some sounds (eg musical notes) contain one main frequency, but most noises contain a mixture of many frequencies and levels. Low frequency waves are far apart (eg the throbbing of a ship's engine or thunder) while high frequency waves are close together (and sound shrill like a whistle or sizzling bacon).

Frequencies are measured in terms of hertz (Hz) or waves per second and people with good hearing can hear sounds with frequencies between 20 and 20,000 Hz. Our ears are more sensitive to high frequency noises than low - noises between 2,000 and 4,000 Hz appear louder and are more damaging than noises with similar amounts of energy at other frequencies.

The effect of frequency on noise measurements

Noise levels can be modified to reflect the varying potential for damage to hearing of different frequencies. These A-weighted levels are expressed in terms of dB(A).

Note that the frequencies present in a noise can be determined, and since they are related to the motion of their sources, this knowledge can be used to identify targets for noise reduction.

How much noise is dangerous?

The level at which noise will start to cause damage in a particular individual is not known since people respond differently to noise. Anything over normal environmental levels could cause a problem.

What is the exposure standard in WA?

In Western Australia, legislation sets a workplace exposure standard of 85 dB(A) averaged over an eight hour period, or a peak noise level of 140 dB(C). Where these values are exceeded, all practicable measures must be taken to reduce the noise level by engineering noise control. Failing this, ways must be explored to reduce the exposure time by half for every 3 dB the level is above the exposure standard.

The noise control and hearing conservation programme

All the activities essential to an effective commitment to noise control and hearing conservation in the workplace should be co-ordinated in a structured programme. These activities include training, noise assessments, noise control, administrative controls and the effective use of personal hearing protectors.

Training

Hearing loss is an insidious problem, happening slowly over a number of years and usually only recognised too late when the damage has already been done. Training has an important role in alerting people to the danger of noise. This knowledge provides the most compelling incentive for involvement in noise control and hearing conservation programmes. As all levels of employers, contractors and workers must necessarily be involved in implementing the programme, it follows that all levels must also be aware of the danger of high volume noise.

How big is the problem? - the noise assessment

When a problem has been identified but cannot be removed immediately, the extent and magnitude of the noise must be determined through a noise assessment. An assessment details the levels present, the items causing the most noise and the people affected by the noise. Thus, priorities for noise control can be worked out. In addition, where immediate changes cannot be made to solve the noise problems, suitable models of personal hearing protectors for the situation can be determined.

Reducing the noise at source

The most effective and acceptable way to reduce noise in the workplace is to change the noise source (such as a machine) so that it makes less noise. This may mean using a quieter process instead of a noisy one (such as pressing rather than hammering), reducing the amount of metal to metal impact, treating radiating panels or using vibration isolation mountings.

If the noise cannot be stopped, then try to stop it from reaching people. This may be done by moving the item further away, by enclosing it or partitioning it off from quieter areas, by using sound-absorbing materials to reduce the build-up of noise or by using silencers.

Some processes, such as metal and stone cutting and grinding, involve rapid distortions of material, producing high noise levels. Until such time as they can be quietened or the processes replaced, some other method must be used to prevent hearing loss.

Reducing noise exposure

Where the high noise levels cannot be reduced, the next line of attack is to reduce the exposure to the noise. This could mean both reducing the number of people in the vicinity of the noise and reducing the period for which those people are exposed, for example by:

  • scheduling the noisy work for times when as few workers as possible are present; 
  • isolating the noisy machinery from as many workers as possible to reduce the number at risk; 
  • using job rotation where practical to alternate noisy tasks with quiet ones and reduce the overall sound energy experienced.

Using personal hearing protectors

Personal hearing protectors should not be used as a substitute when engineering noise control or limiting exposure times are practicable. However, in situations where all measures have been undertaken but the reduced noise exposures are still above the exposure standard, personal hearing protectors must be supplied. They must also be supplied as an interim measure while the engineering noise control or time limits are being planned and implemented.

It is important that they must be chosen for their noise reduction characteristics, comfort and suitability for the job.

The hearing protectors must be worn at all times workers are in hazardous noise. In high noise levels, removing the hearing protectors for very short periods (as little as half a minute) can drastically reduce the overall protection received.

Remember! Uncomfortable equipment will not be worn. Since comfort is a matter of personal preference, a choice of hearing protectors should be provided.

Monitoring the programme - regular hearing tests

A valuable check on the success of the noise control programme can be obtained through the regular audiometric testing of people exposed to noise. The acuteness of hearing at different frequencies, compared from year to year, shows up any trends of hearing loss. As hearing loss usually occurs in the high frequencies first, the noise may be able to be reduced before the damage spreads to the range vital to communication.

Regular audiometric testing also provides a unique opportunity for employee training. The individual assessment usually leads to greater interest and concern for hearing and provides the opportunity to answer individual concerns about noise control and hearing conservation precautions.

(Note: The Workers' Compensation and Injury Management Act and regulations require certain hearing tests and audiological assessments to be carried out for compensation purposes. For further information on this, contact WorkCover WA.)
 

Noise control - an on-going commitment

An effective noise control and hearing conservation programme must be an on-going programme. Machinery should be maintained, maximum noise levels should be specified for new machinery and building extensions and alterations should be planned taking noise into account.
 
Also, to preserve their effectiveness, noise control measures should be monitored and maintained.
 

Act Now!

Excessive exposure to noise causes hearing loss which may be accompanied by tinnitus. Both these conditions lead to a reduction in the quality of life and should be prevented. In the workplace this can be achieved through a noise control and hearing conservation programme. 

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