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Sound Counsel

Published: 29th May 2014 in OSA Magazine

Undesired, unpleasant and loud are all ways that the Oxford English Dictionary describes noise. When it comes to your workplaces, noise can be damaging for workers and lead to devastating consequences.

Imagine that because of the work you do, when you return home in the evenings you can’t sleep because of the ringing in your ears, you can’t hear your partner call your name or the children badgering you for attention. We have the right to finish our day’s work in the same physical and mental state as we started it. Ill health should not be the result of poorly controlled noise levels in the workplace.

Background

The noises within the workplace not only cause hearing problems, but can also affect your performance at work, including being able to read effectively, attentiveness, problem solving and memory. Who would have thought that a noise can prevent you from remembering simple work tasks?

Noise can also be the cause of accidents due to reduced signal recognition, limited auditory localisation and speech communication, misunderstanding oral instructions, and masking the sounds of approaching danger or warnings.

Asia is the most populated continent and its population is estimated at four billion people. This represents 60% of the world’s current human population. In China alone from 1979 to 1991, the number of industrial enterprises increased by a factor of 12, and the number of employees has multiplied by 2.4 times.

Due to a high trend in the production of products including footwear, it has created issues within workplaces including the sources of noise emissions. Some countries within Asia will have periodic measurements and actions taken to reduce hazardous noise, but this can’t be said for the developing countries. Due to the high number of sources of noise emissions most Asian labourers are exposed to controllable noises within the workplace every day.

Unfortunately, noise is a well known hazard within the workplace around the world and in all industries, whether you work in manufacturing, construction, leisure, entertainment or administration. On average, 20 percent of the workers in Europe are exposed to preventable loud noises within their workplaces. Around 30 million people in the United States are occupationally exposed to hazardous noise. And since 2004, the USA Bureau of Labor Statistics has reported that nearly 125,000 workers have suffered significant permanent hearing loss.

In other parts of the world measurements during the manufacture of textiles in Nigeria have recorded noise levels in excess of 130dB (A) which is equal to a marching band of 200 members, or a machine gun.

The results of an audiogram in a study with employees at an airport in China revealed a 41 percent prevalence in high frequency hearing loss in all workers. In the European Union, 28 percent of workers surveyed reported that at least one fourth of the time, they were occasionally exposed to noise loud enough to raise their voices to hold a conversation – this in itself is infuriating and can cause stress too.

Due to the natural resources that Asia has, including petroleum, forests, fish, copper and silver, millions of the workers are employed within manufacturing companies. These companies will produce a high amount of noise which will be hard to control due to the lack of information available to the developing countries.

Many of the developing countries do not have controls in place. This is due to the lack of legislation regarding noise emissions, or simply due to the lack of personnel from local governments to inspect factories.

Another problem within Asia is that the ILO (International Labour Organization) suggested every country should have at least one inspector for 10,000 workers. In China there is one inspector for 35,000 workers. As a consequence, there isn’t much, if any enforcement of protection from noise, and so noise levels are very high with little protection. In mainland China, a textile mill employed approximately 618 female workers, all of whom were being exposed to 84-103dBA.

According to European and national sources you are at a higher risk if you have a full time, non permanent contract or are a younger worker, as you are more likely to be affected by loud noises. They suggest that these two groups of people receive less information regarding health and safety issues, less training and less formal supervision and control in the workplace. This should not be happening within your workplace and employers should be encouraged to ensure everyone has the same information, training and supervision.

The Health and Safety at Work Etc Act 1974 places a duty on employers within the UK to their employees to provide information, instruction, training and supervision – this includes everyone who is working at their business.

What’s all the noise about noise?

Sound is a form of energy. This energy is transmitted through the air as pressure waves. The ear then detects these pressure waves and they are perceived as a sound, or noise.

When sound waves enter the outer ear, the vibrations impact the ear drum and are transmitted to the middle and inner ears. The middle ear has three small bones inside and they amplify and transmit the vibrations generated by the sound to the inner ear. The inner ear contains a snail like structure called the cochlea, which is filled with fluid and lined with cells with tiny hairs. These hairs are microscopic and move with the vibrations and convert the sound waves into nerve impulses –the result is the sound that is heard. Constant exposure to loud noise can destroy these hair cells, which will then cause hearing loss. The hair cells will not grow back and hearing will not be restored, leaving permanent hearing loss.

Decibels is a logarithmic measure of the ratio between numbers and are measured on a logarithmic scale, which means that a small change in the number of decibels results in a huge change in the amount of noise and the potential damage to a person’s hearing.

The loudness of the noise is measured in units of sound pressure levels. These are known as decibels and are abbreviated to dB. A-weighting is a measurement scale that approximates the ‘loudness’ of tones, and is normally used to evaluate environmental noise. This is measured as dB(A).

The technical angles

There are many terms within health and safety, e.g. directives, regulations, legislations, codes of practise and standards. These all mean and do different things, but are all to be abided by as they make up the laws that people follow in their working lives.

While legislation is still emerging in Asia, readers would do well to acquaint themselves with systems already in place to safeguard worker safety. In Europe, for example, directives are a legal act provided for in the EU treaty.

A directive is binding in its entirety and obliges Member States to transpose it into national law within set deadlines. A directive enters into force once it is published in the official journal of the EU.

The directive that has been set for noise at work in Europe is the 1986 EEC Directive on Occupational Noise Exposure1. This exists to provide protection to all workers from harm caused by exposure to noise. It was originally the 1986 EEC Directive and was then altered in 2002, as it was decided by the European Union that a new directive would be released covering the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents like vibration.

A second step was also considered to ensure that the new directive covered measures to protect workers from the risks arising from noise owing to its effects on the health and safety of workers, in particular their hearing. This not only addressed individual workers, but sought to create a minimum basis of protection for all community workers in order to avoid possible distortions of competition. There are also requirements within the Machinery Directive and the Outdoor Machinery Directive which make it clear that prevention through design is important in dealing with occupational noise.

In addition to the above directives’ one of the most used global standards is the ISO 1999:2013 acoustic-estimation of noise-induced hearing loss. ISO is a standard, a document that provides requirements, specifications, guidelines or characteristics that can be used consistently to ensure that materials, products, processes and services are fit for their purpose.

There are more than 19,500 published standards. The specific standard ISO 1999:2003 specifies a method for calculating the expected noise induced permanent threshold shift in the hearing threshold levels of adult populations due to various levels and durations of noise exposure.

Threshold shift is an increase in the hearing threshold – the sound level below which a person’s ear is able to detect any sound – for a particular sound frequency. The hearing sensitivity decreases and it becomes harder for the listener to detect soft sounds. These threshold shifts can be permanent or temporary.

The standard provides the basis for calculating hearing disability according to various formulae when the hearing threshold levels at commonly measured audiometric frequencies, or combinations of such frequencies exceed a certain value. The measure of exposure to noise for a population at risk is the noise exposure level normalised to a nominal eight hour working day, LEX, 8h for a given number of years of exposure. It is applied to noise at frequencies less than approximately 10 kHz which is steady, intermittent, fluctuating, and irregular.

A further Directive’ 2003/10/EC’, was published on February 6, 2003, and is the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents – noise. The Directive sets exposure limit values and exposure action levels in respect of the daily noise exposure and peak sound pressure. This Directive sets these limits at:

• Exposure limit values: LEX, 8h = 87 dB (A) and peak = 200 Pa (1) respectively
• Upper exposure action values: LEX, 8h 85 dB (A) and peak = 140 Pa (2) respectively
• Lower exposure action values: LEX, 8h = 80 dB (A) and peak = 112 Pa (3) respectively

These above levels differ across the world. In China, for example, the eight hour average A-weighted sound pressure level is 7-90 and the upper limit for peak sound pressure is 155dB. This is very high and is equivalent to a fire cracker going off, or the loudest speakers in the world. The levels are too high and have a high risk of causing ill health in workers. Ear protection alone would not reduce the noise enough for it to be a low risk noise.

In India, the eight hour average A-weighted sound pressure level is 90, and the upper limit for peak sound pressure is 140dB. In the United States, however, about 9 million workers are exposed to time-weighted average sound levels of 85dBA and above.

Noise prevention

Noise levels in food and drink manufacturing can be between 80-100dB (A) according to the European Agency for Safety and Health at Work. A study carried out within a food processing factory monitored numerous activities.

Jars were being removed by hand onto cardboard covered sheets before being transported by a conveyor to the filling line – this was via a narrow passageway. In addition to being subjected to physical and postural stresses likely to lead to work-related musculoskeletal disorders, the employees at the factory were being exposed to loud noise levels. This was due to the impact noise from the jars. By enclosing a part of the process this reduced the noise exposures from 89 to 77 dB(A) which then gained 12 dB(A) at the workstation.

The Health and Safety Executive (HSE) in the UK carried out studies within various industries, including agriculture. A hammer mill used for the preparation of animal feeds was producing 93dB at 1.2m. To reduce the noise exposure limits, an enclosure was constructed. It was a frame built from wooden battens and self standing, which allowed for air vents to minimise noise seepage. Due to this enclosure the noise levels were reduced by 8dB and the full cost of the solution was £80.00.

A company called ‘Prevent Sweden-Management and labour improving work environment’ had an issue communicating information and good practise by social partners. To help them get the message across they decided on a CD entitled ‘Sound and Noise’. This was launched to provide information and training to companies in Sweden and aimed at a wide range of target groups across a broad spectrum of workplaces. They found that this was an effective way to ensure that information was given out within workplaces to provide information on noise at work.

In 2005, a campaign was launched by the European Agency for Safety and Health at Work for the European Safety week. This campaign, called ‘Stop That Noise’ was produced to raise awareness of noise at work and the risks that it entails. It also aimed to show that noise is not just a hazard within the heavy fabrication industries, but within a wide range of sectors.

What can happen to you?

There are many health problems that can develop due to noise at work. Acoustic trauma or acoustic shock is caused by short bursts of extremely loud noises. This is an issue of concern in call centres when the volume on the telephone is set too high. It can result in sudden hearing damage and over time will cause more permanent damage.

Tinnitus is caused by exposure to excessive noise, which can be caused by using machinery including chain saws, or even from music at a concert if you are working in the entertainment sector. This condition is a constant ringing and buzzing in your ears and occurs when the hairs within the ears are destroyed due to the loud noise over long periods of time. Once the hairs within the ears are destroyed they will not be repaired, causing a lifetime of unpleasant constant noises in the ears.

Temporary hearing loss is known as a temporary threshold shift, which may occur immediately after exposure to a high level of noise. This could be recovered after spending time in a quiet place. Over time, this will result in permanent hearing damage.
There is also evidence of several non-auditory health effects associated with medium level noise. This includes voice problems, stress, cardiovascular diseases and neurological issues. Noise below the levels usually associated with hearing damage can cause regular and predictable changes in the body. Even ‘ear-safe’ sound levels can lead to these health effects if they chronically interfere with recreational activities such as sleep and relaxation, if they disturb communication and speech intelligibility, or if they interfere with mental tasks that require a high degree of attention and concentration.

What can employers do?

Due to the high risk nature of noise, employers are required to control risks at the sources of noise and eliminate or reduce the risks. Personal hearing protection is not to be used as the only source of protection; prevention control measures are to be in place to control or reduce the risk of noise.

The use of controls within the workplace should aim to reduce the hazardous exposures, so the risk to loss of hearing is eliminated or reduced. Noise can be controlled by using engineering controls – these are methods to isolate the noise source, which could involve the redesign of or modification to plant, equipment, and ventilation systems7. Administration controls can alter the way work is done, including the timing of work, policies and other rules7. By putting policies and procedures in place you will ensure there are rules to follow within the workplace and ensure all employees are aware of them by informing them. This could be done in the form of training.

By increasing the distance between the source of noise and the workers, noise exposure will be reduced. Hearing protection devices such as ear muffs and plugs are an acceptable but a less favoured option, and are only used when engineering and administrative controls cannot be provided, or are an addition to the controls.

All hearing protection should come with a SNR (single number rating) number. This number provides the simple estimate of protection it will give the user and is in dB. A basic ear muff will give the wearer an approximate protection of 23 dB and a basic foam ear plug will give an approximate protection of 38 dB.

Protection will only be provided if the PPE is worn correctly, so provide training to employees on how and when to wear protection to ensure it is effective.

Hearing protection may be used for people who are already suffering with hearing damage but is not the only source of protection against noise. Procedures could also be implemented within the workplace to reduce or illuminate the hazards including health surveillance and regular noise assessments within the workplace.

The general principles of prevention when controlling noise at work are to avoid the risks, evaluate the risks that cannot be avoided, combat the risks at source, adapt the work to the individual, adapt to technical progress, and replace the hazardous with the non hazardous.

Noise at work is a high hazard in most industries and is still causing employees and workers all over the world to suffer from ill health. The noise levels would be healthier if they were consistent all over the world to ensure that all employees are receiving the same amount of protection. Continued work needs to be done to ensure the control of noise is carried out within workplaces all over the world and employers are encouraged to ensure that noise reduction measures are carried out within their business.

Published: 29th May 2014 in OSA Magazine

Author


Jo Carter


Jo Carter Bsc (hons) Grad IOSH

Jo graduated from Leeds Metropolitan University in 2013, having studied Safety, Health and Environmental Management. She currently works at IOSH as Information Services Officer, producing information and guidance including the managing of Safe Start Up and the OSH Research Community website.

Working within the research and information services team, Jo’s focus is on supplying quality information in a range of formats
and supporting the research and development fund.


Jo Carter

Website:
http://www.iosh.co.uk


http://www.iosh.co.uk

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