Outdoor noise pollution: measurement of the main factors

In industrial countries and particularly in Europe, a large part of the population considers noise pollution as one of the main environmental disturbances. After the publication of several national laws and regulations, noise predicting methods have been largely improved. In some countries, the predicted acoustic levels have first to comply with the new limitations imposed by these regulations, and secondly to be experimentally verified in situ. In order to give some tools to the engineers, new measurement methods have been elaborated, and some of them standardised. These methods include both the determination of outdoor sound levels as a function of the environmental conditions such as ground composition, presence of noise barrier and atmospheric effects, and the characterisation of the main parameters which can influence sound propagation, such as absorption coefficients of ground and materials covering noise barriers, and diffraction by various obstacles. (author)