The Hierarchy Of Noise Risk Control

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The Hierarchy Of Noise Risk Control

The WHS Regulations require duty holders to work through a hierarchy of control to choose the control measure that most effectively eliminates or minimizes the risk in the circumstances. The hierarchy ranks the ways of controlling the risk of hearing loss from noise from the highest level of protection and reliability to the lowest so that the most effective controls are considered first.

Effective risk control may involve a single control measure or a combination of two or more different controls.

ELIMINATE THE RISK

The most effective control measure is to eliminate the source of noise completely, for example by ceasing to use a noisy machine, changing the way work is carried out so hazardous noise is not produced or by not introducing the hazard into the workplace.

MINIMISE THE RISK

If it is not reasonably practicable to eliminate the source of noise, you must minimize the risk associated with hearing loss so far as is reasonably practicable. This includes ensuring that the noise does not exceed the exposure standard by choosing one or more of the following measures:

  • substitute the hazard with plant or processes that are quieter
  • modify plant and processes to reduce the noise using engineering controls
  • isolate the source of noise from people by using distance, barriers, enclosures and sound-absorbing surfaces.

If there is a remaining risk, it must be minimized so far as is reasonably practicable by implementing administrative controls, and if a risk still remains, then suitable personal protective equipment must be provided and used. These two types of control measures, when used on their own, tend to be least effective in minimizing risks because they rely on human behavior and supervision.

Substituting plant or processes to reduce noise

BUY ‘QUIET’

One of the most cost-effective and long-term ways of reducing noise at work is to introduce a purchasing and hiring policy to choose the quietest plant for the job. This can be done by obtaining information on noise emission (for example, data on sound power level or sound pressure level at the operator position) from the manufacturer, importer or supplier of plant and comparing it to determine the quietest plant.

Ask the suppliers about the likely noise emission under the particular conditions in which you will operate the machinery, as well as under standard test conditions. If you ask the same question to all suppliers you can compare information. Sound power level data will only ever be a guide as many factors affect the actual noise levels experienced by your workers, but it will help you buy quieter machines.

You should purchase or hire only from suppliers who can demonstrate a low noise design, with noise control as a standard part of the machine, not as an optional extra.

CHANGE THE WAY YOU DO THE JOB

A different way of doing the job may provide the same result with a lot less noise. For example, bending metal in a vice or a press is quieter than hammering it into shape, welding is generally quieter than riveting, gluing is quieter than hammering in nails, clipping is quieter than stapling, and lowering materials in a controlled manner is quieter than dropping them on hard surfaces.

Using engineering controls

A good understanding of the operation of the plant or process is necessary when considering ways of minimizing noise at its source.

Examples of engineering control measures include:

eliminating impacts between hard objects or surfaces

  • minimizing the drop height of objects or the angle that they fall onto hard surfaces
  • using absorbent lining on surfaces to cushion the fall or impact of objects
  • fitting exhaust mufflers on internal combustion engines
  • fitting silencers to compressed air exhausts and blowing nozzles
  • isolating a vibrating noise source to separate it from the surface on which it is mounted
  • using rubber mounts and flexible connections
  • ensuring gears mesh together better
  • fixing damping materials (such as rubber) or stiffening to panels to reduce vibration
  • fitting sound-absorbing materials to hard reflective surfaces
  • turning down volume controls
  • changing fan speeds or the speeds of particular components
  • changing the material the equipment or its parts are made of (change metal components to plastic components).

Isolating the source of noise

Examples of isolating the source of noise from workers include:

  • building enclosures or soundproof covers around noise sources
  • using barriers or screens to block the direct path of sound
  • locating noise sources further away from workers
  • using remote controls to operate noisy plant from a distance.

Using administrative controls

Administrative noise control measures reduce the amount of noise to which a person is exposed by reducing the time they are exposed to it. Examples include:

  1. organizing schedules so that noisy work is done when only a few workers are present
  2. notifying workers and others in advance of noisy work so they can limit their exposure to it
  3. keeping workers out of noisy areas if their work does not require them to be there
  4. sign-posting noisy areas and restricting access
  5. providing quiet areas for rest breaks for workers exposed to noisy work
  6. limiting the time workers spend in noisy areas by moving them to quiet work before their daily noise exposure levels exceed the exposure standard.

If you rely on administrative controls, you should conduct regular checks to ensure that they are being complied with.

Using personal hearing protectors

Personal hearing protectors, such as ear-muffs or ear-plugs, should be used in the following
circumstances:

  • when the risks arising from exposure to noise cannot be eliminated or minimized by other
    more effective control measures,
  • as an interim measure until other control measures are implemented
  • where extra protection is needed above what has been achieved using other noise control
    measures.

If the use of personal hearing protectors is necessary, it is important that the hearing protectors are worn throughout the period of exposure to noise. Removing personal hearing protectors for even short periods significantly reduces the effective attenuation (noise reduction) and might provide inadequate protection. For example, a worker wearing a hearing protector for a full 8-hour day will receive the 30 dB maximum protection level. However, one hour without wearing the hearing protector causes the maximum protection level to fall to 9 dB.

Areas, where people may be exposed to hazardous noise, should be signposted as hearing protector areas and the boundaries of these areas should be clearly defined. Workers and other persons, including managers and visitors, should not enter these areas without wearing appropriate personal hearing protectors, regardless of how short the time they stay in the hearing protector area.

Where sign-posting is not practicable, you should make other arrangements to ensure that workers and others know when personal hearing protectors are required. For example:

  • attach prominent warning notices to tools and equipment indicating that personal hearing
    protectors should be worn when operating them
  • provide written and verbal instructions on how to recognize circumstances in which
    personal hearing protectors are needed
  • ensure effective supervision of identified hazardous tasks

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