• 20.04.2015
  • 15:13

Noise is unwanted sound. This can be anything from annoying noise from a ventilation system to health damaging noise from work operations that may cause hearing damage or stress symptoms.

Illustrasjon støyplagerHigh-frequency noise

is damaging to your hearing and it is therefore important to avoid such noise.

Low-frequency noise

is usually less damaging to your hearing, but may represent a danger because it drowns out speech and warning signals. Longer exposure time to low-frequency noise may also give symptoms such as dizziness and nausea. Low-frequency noise may be difficult to avoid, even with hearing protection, because it may propagate directly into the inner ear.

Impulsive noise

is more damaging than other noise. Compared to damaging noise, which often has a constant and prolonged level of noise, the so-called impulsive sounds are especially dangerous. They consist of very short high-intensity noise impulses which rapidly increase in volume. Hammer strokes, compressed air and nail guns are examples of sources of impulsive noise. Our brain perceives a noise with short time duration as weaker than it actually is. The effect of an impulsive sound can be so violent that it may destroy hair cells in the inner ear on only one occurrence.

Exposure time

is another factor that in addition to frequency and noise level, determines the risk of hearing damage. In order to measure noise, a particular apparatus is used to measure the average level of noise over eight hours to simulate a normal workday. For “regular noise”, a so-called «A-filter» is used for the measurement. This takes into consideration the ear’s tolerance curve and gives the best assessment for risk of hearing damage – dB(A). Impulse sounds are measured by means of a so-called «C-filter» - dB(C). A noise level of 80 dB(A) over eight hours, is comparable to a noise level of 83 dB(A) over four hours. An increase of only 3 dB(A) means that you must reduce the exposure time by half. The same applies if you are exposed to several sources of sound. Two machines next to each other, both generating 80 dB(A), give out 83 dB(A).

Risk assessment and noise report

Risk assessments shall be carried out on the noise levels that those whose work on the vessel is exposed to. One must know the level, type and duration of noise exposure too assess whether the noise poses a risk to the crew. The risk assessment shall include a noise inspection report that is to be kept and available to the crew on board. This will confirm whether measured noise values ​​exceed specified target or threshold values ​​specified in Chapter 15 of the Regulations of 01 January 2005 No. 8, on Working Environment, Safety and Health.

Relevant literature:

Ergonomics - noise - vibrations (pdf)

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