Juan Antonio Méndez Sierra

A categorization method applied to the study of urban road traffic noise

The present work summarizes a study of the hypothesis that urban noise can be stratified by measuring street noise according to a prior classification of a towns streets according to their use in communicating the different zones of the town. The method was applied to five medium-sized Spanish towns (Vitoria-Gasteiz, Salamanca, Badajoz, Cáceres, and Mérida) with populations ranging from 218 000 down to 50000 and with different socio-economic characteristics, climate, etc. As the initial hypothesis of the work was that traffic is the main source of urban noise and is also the principal cause of the variability of the sound levels measured in urban settings, the study focused only on the five nonpedestrian categories of streets. The continuous equivalent sound level (Leq) was employed in the statistical analysis as it is commonly used as a general noise index, and other noise indicators such as L(DN) or L(DEN) are calculated from it. It was found that, although differences between the medians were not statistically significant in some of the towns for certain pairs of adjacent categories, the differences between pairs of nonadjacent categories were always significant, indicative of the stratification of noise in these five towns. Further studies on other medium-sized towns and on large towns and small villages would be needed to test whether the present definition of street categories is extensible elsewhere without modification.

Sound Quality in Urban Environments and its Relationship With Acoustic Parameters

Different urban environments were analyzed acoustically, using 32 recordings obtained with binaural techniques of recording and reproduction. The relationships of the perception of pleasantness/unpleasantness as described by a sample of 25 inhabitants of these urban environments with two psychoacoustic parameters (loudness and sharpness) and the traditional measure of equivalent sound level (dBA) were analyzed in two forms, one using a verbal scale, and the other a numerical value for that perception. Highly significant correlations were found between the perception of an environment as very unpleasant and the parameters considered for its acoustic characterization. The mean of the numerical value used to express the sensation of liking was significantly correlated with the three sound parameters.