Sound advice: Hearing protection in the workplace

As seen in BSIF Guide to the UK Safety & Health Industry 2022. Written by Louise Charlton.

From the alarm clock in the morning, to chatting with family, friends and colleagues, and navigating our environment, for many of us hearing forms a vital connection to our surroundings. Our ears distinguish frequency, tone, and can even isolate a particular sound to determine the direction it is coming from. The parts of the ear that perform these complex functions are necessarily sensitive and therefore susceptible to damage by exposure to high noise levels.?

While it is easy to list the ways we rely on our hearing, noticing harm can prove more difficult. Hearing damage is often undetectable until the effects present in a condition such as noise-induced hearing loss (NIHL) or tinnitus, by which point it is irreversible. NIHL can be extremely isolating, having major impacts on lifestyle and mental health. Tinnitus can be very distressing, causing disrupted sleep or insomnia. With 95 new cases of occupational deafness in 2019 reported through the Industrial Injuries Disablement Benefit (IIDB), and an estimated 17,000 UK workers suffering work-related hearing problems reported via the 2017/18 to 2019/20 Labour Force Survey, exposure to harmful noise remains a major risk across many industries. Noise exposure must be controlled effectively now to avoid life-changing hearing problems later.

High level noise

Exposure to high-level noise damages the Corti, an organ located in the cochlea within the inner ear. Damage can be temporary – experienced as ringing in the ears after a loud concert, for example, called temporary tinnitus. Temporary threshold shift is another example, which makes sounds below a certain level inaudible for a period of time following exposure. These conditions are temporary because the Corti recover once exposure has ended. If, however, exposure to harmful noise is experienced on a regular basis, the ears do not have the ability to a healthy state, meaning permanent damage is sustained. Extremely high noise has the potential to cause permanent damage immediately.

The point at which noise becomes harmful is determined by the decibel (dB) level of the sound and the length of time that a person is exposed to the noise. The decibel scale is a logarithmic ratio between any two sound levels. The addition or subtraction of decibels is different to normal linear calculations – adding 3 dB doubles the noise level, subtracting 3 dB halves it.?

Exposure action values and limits designate when noise becomes harmful and how to protect against the effects. In the UK, the overall exposure limit is a daily/weekly average noise exposure of 87 dB or peak sound pressure of 140 dB. Exposure action values set levels at which appropriate action must be taken to protect employees. The lower exposure action value (LEAV) is an average noise exposure of 80 dB or peak sound pressure of 135 dB, requiring employers to provide information and training, and make hearing protection available. The upper exposure action value (UEAV) is an average of 85 dB, or peak sound pressure of 137 dB, and requires employers to take measures to reduce exposure and provide correct hearing protection for employees. Exposure must be reduced to a safe level of 80 dB at the ear using workplace controls and PPE.?

Assessing noise levels

In order to assess noise levels and determine the controls required, a risk assessment must be carried out.?HSE?publications?INDG362and?L108?give information on conducting a noise risk assessment. Noise must be assessed to determine exposure levels in order to identify the controls required. Guidance can provide the sound output levels associated with some machinery or tasks, but often noise levels are measured in the risk assessment.?

On any job, controlling noise effectively begins in the planning stages. Selection of materials, equipment, and processes can reduce noise at source. Following the hierarchy of control, elimination or avoidance of the task altogether is best. This encourages businesses to find alternative ways of working that do not present a noise hazard. If this is not possible, tools can be adapted to reduce sound output. The workplace can be arranged to exclude or enclose noise, creating ‘hearing protection zones’ where noise-emitting processes take place, enabling employees in other areas to work safely without hearing protectors.?

Where personal?hearing protection?is required, it is important to select genuine, quality products offering adequate attenuation. All hearing protectors must be certified to the PPE Regulation, with conformity markings on the product or packaging. Products must conform to the relevant performance standard. The EN 352 suite of standards cover hearing protectors: EN 352-1 and -3 set requirements for?ear defenders,?headband?and?mounted; EN 352-2 gives requirements for?earplugs; EN352-4, -5, -6, -7, -8 cover a range of requirements for electronic products, including level-dependent attenuation, active noise reduction, and communication features.?

A simplified method of identifying appropriate protection and comparing the performance of products is the SNR method. SNR stands for Simplified Noise Level Reduction (or Single Number Rating), indicating the noise reduction offered – the SNR value can be subtracted from the overall noise level to calculate the sound pressure at the ear when wearing that particular hearing protector.

Hearing protectors are tested with three types of noise, H, M, L. The attenuation data showing performance against each of the noises can sometimes be required for selection. Some hearing protection calculations require full attenuation data for H, M, L noises at the following frequencies: 63Hz, 125Hz, 250Hz, 500Hz, 1000Hz, 2000Hz, 4000Hz, 8000Hz.?

Overprotection

Noise is one of the only risks against which it is possible to overprotect. While high-level noise is harmful, sounds such as speech, warning signals, and approaching vehicles are vital for safe and productive working. This means that the highest SNR value is not necessarily best, as high attenuation can isolate the wearer and put them at risk of an accident. A product with performance closest to the required level should be selected, to provide adequate protection without introducing additional risk.

Compatibility

To ensure adequate protection, it is imperative to select compatible hearing protectors, making sure they are fitted correctly and remain so at all times within the hazard zone.?

Ear defenders work by creating a tight seal with the wearer’s ears. This is created through ‘headband force’, referring to the force exerted by the headband or?helmet/?faceshield and attachments. Spectacle frames, respirator straps and other PPE, plus long hair and ear jewellery, can compromise the seal if allowed to pass beneath the ear defender cushion.

Mounted ear defenders must be tested in combination with the helmet(s) and/or faceshield(s)?with which they are intended for use, in order to verify the headband force created by the products working together. Tested and certified compatibility verifies performance, ensuring that the combination provides adequate attenuation without exerting too much pressure, which can overprotect the wearer and cause discomfort.?

Compatibility is an important consideration when selecting earplug hearing protectors. Banded or corded earplugs may be unsuitable due to the risk of becoming caught on or being pulled loose by another PPE item, machinery, or other structures in the workplace. Ear jewellery must be removed where it affects the seal at the ear canal.

Communication

Team communication is key to safe and efficient working but noise in the workplace can make this difficult. The inability to communicate clearly can cause mistakes or misunderstandings, and make wearers feel isolated from teammates, which can be a temptation to remove PPE. It is important to ensure communication can take place, which can be achieved through administrative controls, such as an area of refuge where workers can communicate safely, or by using a dedicated communication solution.?

Electronic hearing protectors offer several benefits for communication. Level-dependent attenuation and active noise reduction enable wearers to hear safe sounds, including speech and warning signals, while attenuating harmful noise. Team communication, mobile calling, and entertainment audio features facilitate communication across sites without the need to remove hearing protection, plus a way to send safety announcements, and play music where permitted. With the electronic features switched off, products provide passive attenuation to a stated SNR value.

Hearing damage can occur slowly, presenting only once it is too late to reverse. To avoid life-changing conditions such as NIHL and Tinnitus it is vital to ensure workplace noise is controlled effectively. Eliminating noise hazards in the planning stage and introducing workplace controls is advised to reduce exposure at source. Where hearing protection is required, it must provide adequate attenuation without overprotecting, be suitable for the wearer and environment, and compatible with other PPE.

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