Development of an effective hearing conservation programme

Development of an effective hearing conservation programme and the growing importance of environmental perception and communication

Approximately 5% of the world's population has hearing loss^(I), defined as a hearing loss of 40 dB in the best of the two ears. In Europe, 7% of workers experience work-related hearing difficulties^(II).
Hearing loss has an enormous impact, not only on our work environment but also on social encounters. It degrades speech perception, especially in noisy environments. Noise-induced hearing loss is the most prevalent industrial disease in the world^(III).

What's that sound?

Sound is a variation of pressure that travels through a medium, for example, air, water, steel, glass, etc. It travels faster in high-density materials like steel compared to low-density media like air. The sound has 'tone' and volume, similar to home music systems, where you can switch highs and lows to alter the 'tone', and control the volume.
Sound conveys different messages, that is, danger, pleasant information, criticism, etc. Noise, on the other hand, is any unwanted sound.

Hearing devices and hazards

The human ear is divided into three parts:

• External ear, including ear canal and eardrum
• Middle ear containing the three small bones that pass oscillations to the inner ear
• The inner ear, with the cochlea, which contains over 20,000 sensory hair cells that convert mechanical oscillation into tiny electrical impulses processed by the brain.

Hearing damage usually occurs during a prolonged period of continuous exposure to loud sounds, but can also occur after exposure to a single event of very loud sudden sound.

Natural hearing loss associated with aging (presbiacusia) is a minor component of hearing disorders. The main cause of hearing loss is induced noise, which is entirely preventable.

Early signs of hearing loss are often ignored due to complacency or 'predominantly male' behaviour which can lead to permanent hearing loss due to lack of early intervention. Noise-induced hearing loss is entirely preventable.

Risk assessment and control of noise hazards

Risk assessment is a key part of the hearing conservation programme. Information on workers' exposure to noise must be collected, which may include:

• Areas/processes that generate a lot of noise
• What are the measured noise levels? Even without control data, do operators have to shout loudly to be heard from about three feet away?
• Operators working there and for how long
• What control measures exist and how effective are they? Have they been maintained regularly?
• Provision of adequate PPE, taking into account any potential risk of insulation from excessive protection that may degrade important voice signals, e.g. fire alarms
• Compatibility of hearing protection with other personal protective equipment (PPE)
• Provision of adequate training to make effective use of all control measures

Hearing protection

Hearing protection has been redefined as harmful noise under PPE Regulation (EU) 2016/425 and included in the higher risk category, such as respiratory protection or fall protection, for example. As a result, there is a physical change in the CE marking from CE to CEXXXX to include the four-digit reference number of the body performing the annual quality audit.

There is a wide variety of different products to choose from depending on the individual user and the workplace environment.

Hearing protectors range from simple disposable foam earplugs to the most sophisticated communication headphones with Bluetooth® communication function.
It is important to select the right product that best suits the individual needs of the user and the workplace. When providing appropriate hearing protectors, it is important to offer a healthy range of earplugs and earmuffs, as one size or type will not suit all users.

Environmental perception and communications

The workplace is a dynamic work environment and it is important to maintain the ability to hear important sounds and warning signs, such as fire alarms and moving vehicles, while protecting the individual from the harmful effects of noise.
It is therefore vital to select the right hearing protectors that offer the right level of protection, bearing in mind that too much protection can create additional safety risks as the wearer's ability to hear important signals may be compromised.

Validation of the adjustment

Once an appropriate hearing protector has been selected, it is important to check the fit and assess the level of protection achieved by the wearer.
There are several studies done on 'Real World Attenuation' which suggest that the level of attenuation achieved in the field is often significantly lower compared to the data generated by the laboratory^(IV). What. Historically, arbitrary figures have been subtracted from laboratory data to compensate for shortcomings in the adjustment technique. This is known as reduction. However, in some situations where the user achieves adequate sound sealing, the reduction may result in over-protection and insulation capable of affecting the ability to hear important sounds and warning signals such as vehicles in motion.
Individual fit tests help to select the appropriate hearing protector for the individual wearer and the work environment.

There are different types of adjustment test systems commercially available on the market, some subjective, some objective and some measuring back pressure. Subjective systems depend on the ability of the test subject to respond to a test signal. If the test subject's hearing threshold is temporarily affected due to social activity (e.g. a rock concert) or a common cold, this could negatively impact the user's ability to respond to the test signal, leading to potentially unreliable results. Other systems involve back pressure measurement, which is simply used to check the sealing of a custom molded stopper, but this type of system does not provide any information on the attenuation characteristics of the device.

The success case focuses on workers on the construction of a major infrastructure project in the United Kingdom involving over 100 operators. What is clear is that a very small percentage of operators achieved the desired level of attenuation for exposure to standardised noise at 90 dB (A) and, after the first intervention by the technician to demonstrate the correct adjustment technique, an overall improvement in the level of protection can be seen. Additional training may be required to achieve the desired level of protection.

In short, hearing conservation is about understanding the risk of noise in the workplace, carrying out an appropriate risk assessment and implementing effective control measures to protect workers from the harmful effects of noise and other non-auditory health effects. In addition, it is important to recognise the need for essential communication while ensuring that the user remains protected from the harmful effects of noise.

See also:

1. WHO - Hearing loss and deafness, 1 March 2020.
2. EU-15 figures. Report published in Eurostat, Work and Health in the EU: a statistical portrait, ISBN 92-894-7006-2
3. World Health Organization, Prevention of hearing loss caused by noise, 1997
4. Canetto P. and Voix J, Hearing Protectors “Real-World” Performance and the European Directive 2003/10/EC”. In addition, the manufacturer shall ensure that the product complies with the requirements of this Regulation. or 2, 221-226.