Noise Exposure at Work

To know whether or not the noise is a risk factor for health at the workplace the employer needs to know the quantity of the noise exposure. For noise there is a “rule of thumb” that if you have to shout to make yourself heard then the noise is loud enough to cause negative health effects. Often you can get an opinion about the amount of exposure by visiting the workplace and listening to the experiences the workers have. Sophisticated measurements are not always needed. If it is difficult to communicate at the workplace, you can assume that the noise level is above 85 dB(A). To quantify the exposure more accurately, there are two different methods for noise measurements;

Measuring Noise Exposure at Work

Area measurements measures the sound in certain areas using a sound level meter. The level of and the different frequencies the noise is composed of is measured in different locations. This is very helpful to map exposure and design sound contour maps, which are often used both at workplaces and in public areas. Such maps are used, for instance, to mark areas where special hearing protection is needed, or used for planning different protective measures, such as noise source isolation.and personal measurements.

Monitoring Noise Exposure at Work

The other method to perform noise measurements are done through small instruments, called dose meters, which are used to monitor the noise levels the worker is exposed to during the working day. The noise dose meters can be used to monitor workers who change their work place or work task during the day. The instrument is attached and placed on the workers shoulder at the beginning of the workday or before performing specific tasks as shown in the video and when the worker notes his activities during the day it may be used to detect specific exposure situations.

In addition, it is possible to evaluate noise levels by theoretical calculations. Specific methods concerning how to perform noise measurements, and how to calculate noise exposure, are thoroughly described in certain ISO standards.

Illustration of typical noise levels related to different activities. ^{© University of Bergen/Arjun Ahluwalia}

Preventing Noise Exposure

The noise measurement information about is important in a risk assessment, followed by necessary actions to prevent negative health effects from the noise. Noise exposure at work can be reduced by several methods.

Noise Reduction at the Source

• Proper maintenance of machines, equipment and workplace. Lack of maintenance often results in more noise being produced by the machines and Equipment, as wear induces slackening.
• Replacement of old equipment with new and/or improved.

Noise Reduction by interruption of the Transmission Route

• Encapsulation of machines/ work processes. Engines or very noisy work processes can be placed/ performed inside a separate room or covered with noise-cancelling materials to reduce the exposure to the workplace.

Noise Reduction by Protection

• Change in working routines. Making sure that no one works only with the noisiest process is important; the workers can rotate on tasks thereby reducing the exposure for any given individual.
• Personal protective equipment such as ear-plugs and ear-muffs. Ear-plugs and ear-muffs can lower noise exposure, especially if the exposure is high-frequency and are the most important acute preventive device for protecting against noise. These devices must be worn correctly if they are to be effective. The workers and companies also need education in how they should use and maintain these protective devices.

In this video link you can see an example on how to fit an ear-plug.

Information – Hearing Conservation Programs

All workplaces with high noise levels need to have strict regulations and requirements and these need to be made evident for the workers. Such workplaces should have a hearing conservation program protecting the workers. The program must be adapted to the specific workplace, but among the important aspects are:

1. Risk assessment including:
   a. The exposures must be evaluated in all relevant areas, and if a work procedure is changed or new equipment is bought new measurements or evaluations must be undertaken.
   b. All workers should be examined with a relevant clinical examination and hearing test at employment and regularly onwards depending on the recommendations made in the risk assessment and taking into account individual variations in thresholds for injuries.
2. Plan for improvement:
   A plan for improvement, with defined responsibilities and a time-frame for actions is needed.
3. The company/workplace must disseminate information and education on noise and hearing:
   When improvements are implemented at a work place, it is necessary to inform the workers involved about the cause of these changes. Also, it is important to note that workers need training in use of new instruments and work routines. If protective equipment will be provided, the workers need regular training in how and why this equipment should be used.

Mobile Noise Exposure Units

It might be a difficult task to examine the hearing ability of workers. Special sound proof rooms are needed, as well as an audiometer. These factors are seldom available at workplaces. Our colleagues in Tanzania developed a solution; using a mobile unit for the hearing tests. The video below demonstrates the use of the unit.

Noise Exposure Laws and Regulations

Many governments have produced their own national guidelines, but they are often based on internationally agreed guidelines. WHO has a publication named “Occupational noise levels: evaluation, prevention and control” upon which many national guidelines are based. This publication states the exposure criteria, occupational exposure levels and states that for continuous noise levels they recommend a limit of 85 dB(A). This level was chosen because it will Ensure the protection of the median of the population against noise-induced hearing loss after 40 years of occupational exposure at this level. They also discuss impulse noise and the limit is here set to 140 dB(A), but this varies nationally, due to differing opinions concerning the effects of number of impulse noise incidents, duration of these and so on.

© University of Bergen/Authors: O.J. Møllerløkken, M. Bråtveit, E. Sunde, B.E. Moen