Noise is an unwanted sound; its intensity (‘loudness’) is measured in decibels (dB). The decibel scale is logarithmic, so a three-decibel increase in the sound level already represents a doubling of the noise intensity. For example, a normal conversation may be about 65 dB and someone shouting typically can be around 80dB. The difference is only 15 dB but the shouting is 30 times as intensive. To take into account the fact that the human ear has different sensitivities to different frequencies, the strength or intensity of noise is usually measured in A-weighted decibels (dB(A)).

It is not just the intensity that determines whether noise is hazardous. The duration of exposure is also very important. To take this into account, time-weighted average sound levels are used. For workplace noise, this is usually based on an 8-hour working day.
What problems can noise cause?
Noise need not be excessively loud to cause problems in the workplace. Noise can interact with other workplace hazards to increase risks to workers by, for example:

• Increasing the risk of accidents by masking warning signals;
• Interacting with exposure to some chemicals to further increase the risk of hearing loss; or
• Being a causal factor in work-related stress.
• Exposure to noise may pose a variety of health and safety risks to workers:

Hearing loss: Excessive noise damages the hair cells in the cochlea, part of the inner ear, leading to loss of hearing. "In many countries, noise-induced hearing loss is the most prevalent irreversible industrial disease. It is estimated that the number of people in Europe with hearing difficulties is more than the population of France.

Physiological effects: There is evidence that exposure to noise has an effect on the cardiovascular system resulting in the release of catecholamines and an increase in blood pressure. Levels of catecholamines in blood (including epinephrine (adrenaline)) are associated with stress.

Work-related stress: Work-related stress rarely has a single cause, and usually arises from an interaction of several risk factors. Noise in the work environment can be a stressor, even at quite low levels.

Increased risk of accidents: High noise levels make it difficult for staff to hear and communicate, increasing the probability of accidents. Work-related stress (in which noise may be a factor) can compound this problem.

Who is at risk?
Anyone who is exposed to noise is potentially at risk. The higher the noise level, and the longer you are exposed to it, the more risk you have of suffering harm from noise. In manufacturing and mining, 40% of employees experience significant noise levels for more than half of their working time. For construction, the proportion is 35% and in many other sectors, including agriculture, transport and communications, the figure is 20%. It is not only manufacturing and other traditional industries where noise is a problem. Noise is being recognised as a problem in service sectors such as education and healthcare, bars and restaurants.

• A study of noise in kindergartens found some averaging noise levels over 85dB
• During a performance of Swan Lake, a conductor was recorded as being exposed to 88dB
• Truck drivers can be exposed to 89dB
• Staff in nightclubs can be exposed to up to 100dB
• Noise on pig farms has been measured up to 115dB

Noise prevention
Noise can be a problem in many workplaces, not just on construction sites and in factories, but anywhere from farms to bars, schools to concert halls. Whatever the workplace, there are three key steps to preventing harm to workers:

Assess the risks
Key points in a risk assessment

• Identify the different noise-related risks in your organisation.
• Consider who may be harmed and how, including temporary and part-time staff, as well as workers in specific risk groups such as employees who are pregnant.
• Evaluate measures that are already in place to control noise levels, and decide what further action needs to be taken to prevent or control the risks;
• Record all your findings and share them with workers and their representatives.

Regularly monitor and review the effectiveness of the measures in place.