$model of sound diffraction$

#MODEL OF SOUND DIFFRACTION SERIES#

In recent years, a number of innovative barriers are being developed, such as combined noise and safety barriers, low-height barriers, photovoltaic barriers, noise walls with titanium dioxide (TiO 2) coating, inox/corten steel barriers, or acoustic devices based on sonic crystals. In the past, simple reflecting barriers made of concrete, masonry blocks, or earth berms were often used, but modern barriers tend to have absorptive treatments which minimize the level of reflected noise. Noise barriers have been made of many different materials and have taken many different forms over time.

$model of sound diffraction$

In the European Union, these devices have become the most prominent noise mitigation measure applied to major roads located outside residential areas in the USA, about 5700 km of barriers have been built to date. As an example of the extensive use of these devices, it was estimated that the global production of noise barriers reached approximately 370 million m 2 in 2014. Constructing a noise barrier is probably the most mentioned mitigation measure in EIAs conducted around the world. As part of the EIA process, the project developer is required to evaluate road traffic noise and must determine appropriate mitigation measures to minimize its effects. Since the 1980s, many countries have adopted Environmental Impact Assessment (EIA) legislation that requires the evaluation of, among others, proposed road projects that are likely to have significant environmental impacts. It was also during this period that the first regulations for noise management and abatement were adopted in countries such as the USA (1972), Canada (1973), Germany (1974) and Japan (1974). Probably the most famous of these studies was the Maekawa empirical chart of 1968, as well as the formulations developed by other authors based on Maekawa’s original proposal. In the 1960s and 1970s, the first research studies were initiated to analyze the acoustic properties of barriers and calculate noise attenuation levels. By 1975, Japan had already built noise barriers along 79 km of new highways, and the USA had installed about 57 km of barriers at certain types of highway projects. And so, the first lightweight barriers with an absorptive treatment on the panel surface date back to the early 1970s. In the following years, several new design criteria and new materials for barriers were rapidly introduced. The first documented noise barrier installed on a road was built in 1963. The history of noise barriers precedes the appearance of the first generation of environmental regulations in the World. Currently, noise barriers have become frequent features along many roads and railways. These included urban planning measures (such as the designation of noise-sensitive areas, or regulations on vehicle speed limits or traffic restrictions), measures to improve the acoustic performance of vehicles, pavements and buildings, and the construction of noise barriers.

$model of sound diffraction$ $model of sound diffraction$

#MODEL OF SOUND DIFFRACTION SERIES#

In the last decades, the introduction of more stringent environmental noise legislation has resulted in a series of noise abatement measures of varied nature. In the European Union, the population exposed to high road noise levels is projected to rise both inside and outside urban areas over the next years due to urban growth and increased demand for mobility. Moreover, the problem is expected to become more severe in the next decades. In Europe, it is estimated that about 20% of the total population is exposed to road traffic noise levels considered harmful to health. Road traffic is the predominant source of noise in urban areas and represents the second most important health risk factor after air pollution. 1.1 Noise barriers: the ubiquitous solution to the road noise problemĬhronic exposure to environmental noise is a widespread problem around the world, causing significant impacts on human health and well-being.

$model of sound diffraction$

Model of sound diffraction