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Noise Pollution (Part 2 of 2)

posted Aug 26, 2010, 9:39 AM by Patricia Martin
Noise Control and Mitigation 

“Noise control is the technology of getting an acceptable noise environment at the receiver end, consistent with economical and operational considerations” (Singal 2005, 228). This definition reveals the complexity that noise control entails. It is a subject that involves many professionals—policy-makers, engineers, architects, and doctors, for example—and has important social repercussions. That is why, even when technically it is possible to avoid urban noise pollution almost completely, some control measures are impossible to apply economically or socially. However, many mechanisms are available today to control and mitigate environmental noise. We can divide these mechanisms into three groups: noise reduction at the source, noise control in the transmission path, and noise control at the receiver end using protective measures (Singal 2005, 229). In order to reach maximum mitigation, it is preferable to deal with the three categories together when dealing with noise pollution problems in cities. 

Frequently, noise control measures are more effective when applied at the noise source. There are several methods to control traffic noise at the source, such as, for example, designing quieter vehicles, removing vehicles from roads by redesigning the traffic distribution, and reducing traffic speed. However, these strategies often result in very expensive solutions that can have very negative effects on vehicles and traffic operation. For example, reduction of noise generated by vehicles involves a great deal of investment in research by manufacturers, and most of the mechanisms interfere with machine operation. Moreover, traffic planning can reduce considerably noise in a city by, for example, constructing road by-passes that absorb high traffic flows. Nevertheless, these actions require huge investments and habitually result in protests by those in the communities affected. In addition to this, the reduction of traffic speed appears to be one of the most effective tools to decrease noise levels, although it is very difficult to achieve in practice. 

Second, noise control in the transmission path is determined basically by the road design and its vertical and horizontal alignment. There are many design strategies that can be implemented in order to minimize noise propagation: tunnels, cuttings, barriers, etc. Each specific case will require a different strategy. For example, in the case of elevated roads, which produce greater environmental noise problems, barriers can mitigate noise propagation noticeably. Roads in cuttings are generally well screened by the surrounding walls, but they can present an obstruction or discontinuity of the urban fabric when placed in cities. Therefore, cuttings are preferable in edge conditions. Tunnels are a perfect solution for noise mitigation, as we can confirm in the case of the Big Dig project in downtown Boston. However, these strategies can be very expensive when dealing with existing structures and therefore should be addressed in very problematic cases. On the other hand, the use of vegetation as a noise barrier has been proven to be a very effective measure in urban areas (Kang 2007, 176). 

Finally, noise control at the receiver end refers mainly to the acoustic insulation of surrounding buildings. The main elements that should be insulated are walls, windows, doors, and roofs, and the degree of insulation is determined by the physical properties of the materials and the type of construction. By using absorbing materials within the free space of frame construction and eliminating paths of transmission, noise propagation inside buildings can be reduced drastically. In addition to this, buildings can be designed in order to minimize the impact of traffic noise on them. The shape and orientation of the buildings play a key role when dealing with noise problems. 

Conclusions and Recommendations 

While the world is becoming more populated and urbanized and our cities denser and condensing more activities, noise pollution is increasing as one of the most important environmental problems. Therefore, citizens, politicians, regulators, architects, planners, engineers, and other professionals should be aware of our huge responsibility to address this issue that affects the whole community. Noise control should be tackled as an essential element in environmental policies and urban planning projects as a crucial factor in improving citizens’ quality of life. In order to reach convenient environmental noise levels, we should continue researching and developing more complete noise policies. For example, due to the complex nature of noise production, we should consider the great diversity and multiplicity of noise sources and the different solutions that are required for each case. Some cases, such as the construction of a new highway or an airport, require considering noise issues when planning its location and the uses of the surrounding areas. In other cases, such as the specific noise generated by engines or industrial machinery, noise should be controlled by legislation and regulations concerning fabrication standards. Therefore, in order to advance with respect to noise control, I recommend: 

· Collecting and developing data regarding the current noise pollution situation in cities through the use of noise maps or other tools with the aim of creating a complete base that can help to identify specific problems, sources, and causes of environmental noise. 

· Once the problems are identified, creating work groups at the local level with the purpose of solving them case by case, taking into account the specific characteristics of each one. 

· Reconsidering current noise limit regulations, since most of the levels allowed are much higher than those recommended to avoid adverse health effects. 

· Promoting further research and study of the mechanisms to manage and avoid noise generation through the creation of environmental programs in schools and universities. 

· Implementing noise impact assessment studies for new projects, which will ensure the minimization of noise generation in the future. 

· Organizing environmental awareness programs referring to noise pollution and directed to citizens and professionals. 

In addition to this, we should emphasize the local character of noise. Usually the source and the receiver are separated by small distances, always inside the context of localities. Therefore, local governments play a key role in noise management issues, and it is in their context where monitoring and regulation processes acquire special importance. Noise pollution can appear to be a problem with easy solutions, since once the noise source disappears, so does the pollution. However, we cannot ignore the fact that noise pollution is increasing in our cities, impacting our health and quality of life, and this trend will continue unless we act on it promptly.

Noise mitigation options [Source: Kotzen, Benz, and Colin English. Environmental Noise Barriers. London: E. & F. N. Spon, 1999].

Examples of self protection buildings [Source: Kang, Jian. Urban Sound Environment. New York: Taylor & Francis, 2007].