NOISE MONITORING & CONTROL
and some bodies are more resilient than others, the human ear is very delicate. Noise exposure is a dose- based concept so exposure to very high levels of noise for short durations, or lower levels for longer durations can both significantly increase the risk of long-term hearing damage.
For example, in the engine room of a ship, the average sound pressure level can be between 105dB and 110dB. If someone entered that area to carry out some maintenance checks, even very short-term exposure could be severely damaging. In this scenario, without wearing hearing protection you could exceed your recommended maximum daily dose of noise exposure in a couple of minutes. In a manufacturing plant where levels might average around 90dB it would take an unprotected worker about 2.5 hours to exceed the maximum daily dose. However, in both scenarios if the worker was regularly exposed to more noise beyond that point, they are likely to incur hearing damage.
This is more common in industries where workers are continually exposed to occupational noise. It is no surprise that research has confirmed that those employed in construction, manufacturing, mining, agriculture, utility, transportation, the military, and musicians are at higher risk of ONIHL. It is therefore important to understand that even if the overall noise level does not appear to be excessive, continued exposure can bring the average level of noise exposure during an eight-hour working day to a level that is likely to significantly increase the risk.
The second type of noise exposure, in contrast, is short-term, impulsive noises of very high level such as gunfire, drop hammers and nail guns. These contribute relatively little to the overall sound energy received, but they carry a disproportionately high risk to the hearing system with risks including instantaneous acoustic trauma as well as damage to the inner ear, and occupations exposed to impulsive noises are at the greatest risk of ONIHL.
BE CAREFUL WITH PERSONAL PROTECTIVE EQUIPMENT An overreliance on personal protective equipment (PPE) is symptomatic of a lack of appreciation of the risks. Equipment like ear defenders should be understood to be a last resort. Occupational and health and safety professionals use the ‘hierarchy of control’ to determine how to implement feasible and effective controls. This approach groups actions by their likely effectiveness and is visualised as an inverted pyramid, with the most effective methods at the base of the pyramid and the least effective at the inverted tip. You might be surprised to learn that protecting workers with PPE is regarded as the least effective.
One common problem with much PPE is that is does not always do what it says on the tin. At KP Acoustics Research Labs, we have worked with many companies to test out noise control products and make sure they can perform in the way intended. As the lab tests are
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carried out in a carefully controlled environment, they often give a significantly higher performance than is ever obtained in the real world. Issues such as quality of fit, user error, and degradation of the item all affect real-world performance of hearing protection – with user error being by far the biggest contributor to real- world performance.
User error is easier to fall into than you might assume. Workers who are regularly in noisy environments
“WORKERS WHO ARE REGULARLY IN NOISY ENVIRONMENTS MIGHT BECOME COMPLACENT AND DESENSITISED TO THE RISKS.”
might become complacent and desensitised to the risks. For example, a common risk unknowingly taken is temporarily lifting your ear defender to have a conversation in a noisy area, instead of moving to a quieter area. In this scenario, the amount of sound energy in that few moments could be enough to exceed the daily amount of energy that is known to be likely to lead to hearing loss. The ear defenders haven’t done their job. Another key error is incorrect insertion of earplugs by untrained users, which can reduce protection by as much as 20dB.
If you want to be part of the change that allows us to tackle the world’s single greatest occupational health disease then educating yourself and your employees is the best place to start. Greater awareness and understanding of the risks can lead to the behavioural and administrative changes necessary to keep us safe at work.
www.kpacoustics.com
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