Valentín Gómez Escobar

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.

Possible relation of noise levels in streets to the population of the municipalities in which they are located

A preview of the results of applying a categorization method to twenty towns with populations between 2200 and 700 000 inhabitants and areas between 0.57 km(2) and 59 km(2) is presented. This represents a significant expansion of the population size and area of urban sites studied by this method, with variations of two to three orders of magnitude, including the fourth most populous town in Spain. It is found that there is a relationship between urban noise and inhabitants, and also between urban noise and inhabited area, reflecting the urban structure defined in the strata of the categorization method.

Urban streets functionality as a tool for urban pollution management

Pollution derived from traffic can be considered one of the major problems of modern cities. Although considerable efforts have been devoted to gathering information about pollution and its control, little attention has been paid to the analysis of relationships between pollution distribution and town planning. The existence of these relationships would enable better prediction and prevention of pollution through town planning. In this work, an analysis of one pollutant derived from traffic (urban noise) in 27 cities is presented. Non-parametric tests and ROC analyses were employed, using the equivalent sound level (L(eq)) values as the dependent variable. For the characterization of the pollutant, an alternative concept to accessibility is analyzed: the concept of functionality. Results of statistical inferential analysis showed the existence of significant differences between the sound levels of the different category results, confirming that noise is stratified in the studied cities and that the five categories proposed based in the concept of functionality highlight this noise stratification. Moreover, high sensitivity and low non-specificity were obtained by using ROC analysis. Results of this analysis also showed an overall average value of prediction capacity close to 90%. Therefore, because the proposed categories highlight the noise stratification of the studied pollutant in all the towns studied, the functionality concept can be considered an interesting tool for urban planning and for designing pollution prevention policies. Finally, as traffic is a source of other urban pollutants, the concept of functionality may be a new concept for wide environmental pollution management.

Analyzing nocturnal noise stratification.

Pollution associated to traffic can be considered as one of the most relevant pollution sources in our cities; noise is one of the major components of traffic pollution; thus, efforts are necessary to search adequate noise assessment methods and low pollution city designs. Different methods have been proposed for the evaluation of noise in cities, including the categorization method, which is based on the functionality concept. Until now, this method has only been studied (with encouraging results) for short-term, diurnal measurements, but nocturnal noise presents a behavior clearly different on respect to the diurnal one. In this work 45 continuous measurements of approximately one week each in duration are statistically analyzed to identify differences between the proposed categories. The results show that the five proposed categories highlight the noise stratification of the studied city in each period of the day (day, evening, and night). A comparison of the continuous measurements with previous short-term measurements indicates that the latter can be a good approximation of the former in diurnal period, reducing the resource expenditure for noise evaluation. Annoyance estimated from the measured noise levels was compared with the response of population obtained from a questionnaire with good agreement. The categorization method can yield good information about the distribution of a pollutant associated to traffic in our cities in each period of the day and, therefore, is a powerful tool for town planning and the design of pollution prevention policies.

Acoustical performance of porous absorber made from recycled rubber and polyurethane resin

This paper reports an investigation of a new kind of material and its acoustical performance. The main component of this porous absorber is the ground tyre rubber (GTR) with different particle sizes, from the shredding of tyres of heavy vehicles, mixed with different proportion of polyurethane resin. Acoustical properties were assessed according to ISO 10534 - 2: 1998. The data obtained show porous absorbers having a high sound absorption performance with low thicknesses and compared to some of the current models for the prediction of their absorptive properties. The use of this model constitutes a good tool in order to design a new sound absorber to solve two environmental problems, noise and environmental pollution.

The performance of resilient layers made from cork granulates mixed with resins for impact noise reduction

This paper analyses the impact noise reduction of resilient layers made from cork granulates with eight different sizes, mixed with polyurethane and epoxy resins. The predicted impact sound improvement index and dynamic stiffness are compared with some commercially available underlays. According to the type of binder and particle size, the acoustical cork based layers present values of the impact sound improvement index and dynamic stiffness similar to the commercial layers used in buildings.

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.