NOISE a worldwide problem one of the strongest inequalities at subregional and national levels
What is Sound? • Sound is any pressure variation that can be detected by the human ear. • Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas. What is Noise? • Noise is unwanted sound.
Noise caused by industry and infrastructure is a major source of dissatisfaction with the environment in residential areas. In order to assess and monitor the influence of noise, policies on noise control have been developed in most European countries. Noise effect studies are carried out to support these policies. The result of different studies can only be combined or compared if the same indicators for noise exposure and the same assessment methods are used. It is therefore important to develop standardised methods for noise mapping. This is recognised by the DG Environment of the European Commission, who is preparing a Directive on Environmental Noise. This article illustrates and underlines the essence of standardised noise mapping tools. It also describes considerations for the development of these tools and focuses on: accuracy; cost-benefit criteria for noise measures; and presentation of uncertainties in results.
Geographical Information Systems (GIS) play an important role in noise mapping. An appropriate use of GIS in mapping noise effects makes it possible to optimise quality and efficiency of noise effect studies. Standardisation will benefit from the possibility of automating the noise mapping process in GIS. Furthermore, GIS can play an important role in estimating and exposing uncertainties.
Software There are several models for making noise maps. Some of them use empirical models (for instance, INM for airports noise mapping), but most of the models are based in the physics of propagation of sound outdoors (defined in ISO 9613). The use of these software packages is quite easy, and the accuracy of results is very high depending on the quality of input data to the models. Measurements are used very often for the validation of results. • For train and road traffic noise, the description of the sources is usually made in terms of easy to know parameters, such as speed, number of vehicles etc. The main challenge for the acoustic consultant is the creation of good digital terrain model (DTM). • For industrial noise map production, the most important thing is the description of noise sources: sound power levels, directivity, working periods. Although some databases can be found, in many cases it is necessary to make measurements (ISO 3740) for describing the source. When these data are known, it will be necessary to simulate each of sources using a combination of point, line or surface noise source. The creation of good acoustic models can be quite complicated, and only experienced consultants can front this difficult tasks. • Simulation tools are very useful specially at planning stages, where measurements are not possible. The consultant can evaluate the effectiveness of action plans, in order to take decisions.