Sound propagation in woods. Comparative analysis between in situ measurements, laboratory measurements and the values predicted by a theoretical model (Spanish text)

This PhD Thesis studies sound propagation outdoors and the potential effect of trees on such propagation.; In the first part of the thesis, seven different types of grounds (sand, grass, concrete…) are characterised from an acoustical point of view. In order to determine the ground impedance of each type of ground, it was necessary to determine the flow resistivity by means of an indirect method. In this method the flow resistivity values are chosen so as to give the best fit between experimental values and the values given by a theoretical propagation model.; This first part includes a comparative analysis of sound attenuation over two very similar types of grounds, one with trees and the other one without trees. It is observed that at high frequencies sound attenuation in the case of ground with trees (wood) is higher.; In the second part of this work, the theoretical outdoor sound propagation model NORD 2000, which has been developed by a group of scientists in the Scandinavian countries, is described and then validated. This model takes into account the source characteristics, the geometric divergence, atmospheric absorption, ground effects and the scattering produced by obstacles such as trees, houses… In order to validate this theoretical model, we have compared the predictions given by the model under many different circumstances with the values measured in situ in different types of woods and also with the values measured in a scaled model in laboratory, using different trees density, trunk diameters… From a deep analysis of all the set of comparisons it was concluded that the theoretical model NORD 2000 agrees very well with the experimental values both measured in situ and in laboratory (scale model) at low and medium frequencies. At high frequencies there are some discrepancies between the model and the experimental values.