Sound advice: Hearing protection in the workplace

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.?

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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 an estimated 22 million US workers exposed to work-related hearing problems according to the National Institute for Occupational Safety and Health (NIOSH) 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 recovers 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.

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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.?

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Assessing noise levels

Under OSHA’s Noise Standard, the employer must reduce noise exposure through?engineering controls, administrative controls, or Hearing Protection Devices (HPDs)?to attenuate the occupational noise received by the employee’s ears to within levels specified in Table G-16 and Table G-16A of 29 CFR 1910.95(b)(1).

OSHA requires?employers to implement a hearing conservation program when noise exposure is at or above 85 decibels averaged over 8 working hours, or an 8-hour time-weighted average (TWA). Hearing conservation programs strive to prevent initial occupational hearing loss, preserve and protect remaining hearing, and equip workers with the knowledge and hearing protection devices necessary to safeguard themselves.

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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.?

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Where personal?hearing protection?is required, it is important to select genuine, quality products offering adequate attenuation. All hearing protectors must be tested to the relevant ANSI standard and supplied with complete user information and instructions.

A simplified method of identifying appropriate protection and comparing the performance of products is the NRR method. NRR stands for Noise Reduction Rating and indicates the noise reduction offered by a particular hearing protector.

Hearing protectors are assessed with test sounds at the following frequencies: 125Hz, 250Hz, 500Hz, 1000Hz, 2000Hz, 3150Hz, 4000Hz, 6300Hz, 8000Hz. The mean attenuation and standard deviation values at each frequency are given in the product's user instruction manual.

?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 NRR 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.?

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Ear muffs 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 jewelry, can compromise the seal if allowed to pass beneath the ear defender cushion.

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Mounted ear muffs 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 compatibility verifies performance, ensuring that the combination provides adequate attenuation without exerting too much pressure, which can overprotect the wearer and cause discomfort.?

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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 jewelry must be removed where it affects the seal at the ear canal.