For decades now we have understood the health impacts of noise and the long-term damage to our hearing. There is a requirement for workplaces to try to reduce noise levels to below 85 decibels if it occurs over an 8-hour period. You are not to expose your employees to a noise level above 140 decibels. However, hearing damage is related to the intensity of the sound, the nature of the sound (whether it’s continuous or intermittent) and the duration of the noise exposure. So long term exposure to low-level noise can also create permanent hearing loss.
The Code of Practice: Managing Noise and Preventing Hearing Loss at Work under the Australian Work Health and Safety legislation defines hazardous noise about hearing loss as
noise that exceeds the exposure standard for noise in the workplace.
Between 28% and 32% of Australian workers are likely to work in an environment where they are exposed to non-trivial [>84dB(A)] loud noise generated during their work.
In this article, we summarise a Chapter on Occupational Noise by the OHS Body of Knowledge to provide the key concepts and advice to help you manage noise hazards in your workplace. We provide a basic understanding of acoustics and the factors that impact hearing loss and health together with the principles of noise measurement and control.
When Can Noise Damage Hearing?
The first indication that noise may be hazardous to hearing is when a person has to raise their voice to talk to someone who is about an arm’s length away in a noisy workplace.
There is a simple test that you can do to assess the effects of occupational exposure to noise and its impact on your hearing.
- Drive to work and switch off the engine, but not the ignition.
- Switch on the car radio and reduce the volume so you can just hear it.
- Do not switch off the radio, but switch off the ignition and go to work.
- After work, switch on the ignition. The radio should come on as well.
- If the radio cannot be heard, a temporary shift to your hearing ability has occurred during the workday.
This change in your hearing ability may last from hours to days after the exposure. Generally, hearing recovers overnight, giving a false impression that all is well. However, the effects of regular exposures are cumulative as the hair cells in your inner ear are eventually destroyed.
How Do You Measure Noise?
A noise assessment can be carried out with a sound level meter (SLM) or a noise dosemeter (NDM). In recent years noise dose badges have become available. A noise dose badge is a smaller version of the traditional noise dose meter with no cable between the meter and microphone that can get in the way of the work. An SLM is usually handheld and therefore the assessor is present as the measurements are made; this has the advantage that the assessor can observe firsthand what is being measured. An NDM is designed to be worn on a person for a period of time while that person carries out their work.
What is Noise-Related Stress?
Noise related stress factors include stress, irritability, headaches, moodiness and insomnia, disturbance of psychomotor reactions, loss of concentration, and speech interference. Health-related effects include; reduced productivity, reduced quality of work or service, and increased absenteeism. All of these affect the productivity of your workforce.
How Can You Control Noise Hazards?
Where noise sources have been identified, the next step is to prioritise noise control by determining the duration of use of each machine or item of equipment during a typical shift and the time the operator spends using them or working near them.
For example, a machine or piece of equipment with a high noise level, but with short usage per shift may well have a lower priority for noise reduction than a machine or piece of equipment with a lower noise level, but long usage per shift. For example, a milling machine operated for six hours per day at 88 dB(A) at the operator’s ears, needs more urgent noise reduction than an auger operating for 15 minutes per day at 94 dB(A).
How Can You Eliminate or Minimise Noise Hazards?
The Australian Work Health and Safety legislation requires that workplaces follow the hierarchy of controls. Workplaces cannot automatically rely on the use of hearing protectors, or other forms of personal protective equipment, where it is reasonable and practicable to use higher-order controls. However, the provision of hearing protection is the most common method organisations use to prevent hearing loss.
Workplace noise that exceeds the exposure standard must, so far as reasonably practicable, be reduced to non-hazardous exposure levels where you eliminate the hazard. One way of doing this is by no longer carrying out the work that creates the noise. Where this is not practicable, you should substitute the activity or process by changing the noisy components for quieter ones. For example, instead of hammering a piece of metal to bend it, the metal could be heated and then bent with pliers or a press. Workplace noise can also be minimised through design by replacing old plant and equipment with new quieter plant and equipment.
The Tap into Safety online and mobile-friendly Training Platform has a course that trains about the Hierarchy of Controls with real working examples of the triangle. The course uses microlearning together with a robust assessment, report and certificate. Also, many of our safety training courses cover Noise Hazards and how to control them to protect long-term hearing loss.
See our article, Workplace Hazards and the Hierarchy of Controls.
How Can Engineering Controls Help?
Engineering noise controls modify the noise source itself or through enclosures, that may be made from a solid material and lined internally with a sound-absorbent lining. You might also add silencers or mufflers to existing noise sources or place barriers in the noise path or enclose the receiver end by creating a control room. Generally, engineering noise control is the most effective way of controlling noise, but may sometimes be cost-prohibitive.
Some practical examples of engineering noise control include:
• Mounting vibrating sources within machines on isolators or dampeners
• Replacing metal components with quieter materials such as plastic, nylon or compound components
• Installing local enclosures around particular noisy machine components
• Adding sound-absorbent materials
• Providing air and gas exhausts with silencers
• Changing to a quieter type of fan, fan blade pitch or the number of blades, or fitting sound attenuators in ventilation ducts.
Using Administrative Control Measures
Administrative noise control measures aim to reduce the amount of noise you expose your employees to via organisational methods, for example, delineating hearing protection areas,
noise mapping to identify safe and unsafe noise areas, rescheduling workers’ duties to limit exposure times, and optimising maintenance.
See our article, Can Employees Recognise, Recall and Report Workplace Hazards?
PPE: Hearing Protection
Hearing protectors should be worn where hazardous noise levels exist in the workplace that cannot be reduced by higher-order controls. There are three types of hearing protectors:
• Disposable or individually moulded earplugs
• Ear canal caps
• Passive or active earmuffs.
Passive earmuffs are the conventional type while electronically active noise level-dependent earmuffs allow noise up to 82 dB to enter the ear after which an electronic system shuts the reception down and they act like passive earmuffs. Noise-cancelling earmuffs reduce low-frequency noise by monitoring the noise environment outside the earmuff.
The ideal in-ear noise level under the protector should fall between 75 and 80 dB(A) to reduce workplace noise to safe levels while enabling hearing and communication without over-protection and the temptation for your employees to remove the protector in noisy environments.
See our article, How to Choose Effective Hazard Control Measures.
Do Hearing Protectors Control Noise?
Many people hold the common misconception that hearing protectors control noise. Hearing protectors do not control workplace noise as the noise in the workplace is still there but the wearing of a hearing protector reduces the in-ear noise level. However, exposure is not reduced by the wearing of personal hearing protectors.
When your organisation needs to provide hearing protection,
• Selection and management should be done by a suitably qualified person
• You need to train how to correctly fit and wear it
• Your procedures should insist that your employees fit the hearing protectors before entering the noisy work area
• You need to ensure regular cleaning, maintenance and secure storage
• You need to mark areas where hearing protection is required
• Always keep appropriate documentation
• You need to regularly monitor the effectiveness of the hearing protection use.
All organisations have a duty to protect their employees hearing. Long-term hearing loss is classified as one of the eight priority diseases in Australian workplaces. You are encouraged to use the safety hierarchy of controls to eliminate noise hazards using the highest level of control as far as reasonably practicable. Where this is not practicable, you should substitute the activity or process by changing the noisy components for quieter ones. Workplace noise can also be minimised through design by replacing old plant and equipment with new quieter plant and equipment. Engineering noise controls modify the noise source itself or through enclosures, silencers or mufflers.
Lower-order controls such as Administrative noise control measures delineate hearing protection areas, identify safe and unsafe noise areas, reschedule workers’ duties to limit exposure times, and optimise maintenance. Hearing protector PPE should be worn where hazardous noise levels exist in the workplace that cannot be reduced by higher-order controls. However, hearing protectors do not control workplace noise as the noise in the workplace is still there but the wearing of a hearing protector reduces the in-ear noise level.
Damage to hearing and exposure to noise cannot be undone or repaired. It is therefore imperative that your employees wear their hearing protector PPE at all times in noisy areas and you do what is practicable to reduce noise hazards.
This article is also available on the Tap into Safety Podcast.