Environmental noise indicators and acoustic indexes based on fuzzy modelling for urban spaces

Abstract

This paper presents six environmental noise indicators and two fuzzy acoustic indexes for urban spaces integrated with a permanent monitoring system. Likewise, they can help the management practices of land traffic and other noise generation sources in cities. The environmental noise indicators are defined by combining the equivalent continuous sound levels with A-weighting for time intervals of five, thirty, and sixty minutes and the non-harmful values set by national and international standards. Exposure and severity are the fuzzy indexes obtained with a model that weights the six environmental noise indicators utilising membership functions, rules and the centroid defuzzification method. The two fuzzy indexes are evaluation metrics of the social-urban acoustic impact that monitoring and evaluation programs can apply for standard time intervals or other time selection.Assessment traditional methods use the equivalent continuous sound level by integrating the sound pressure for a short or long time. When the analysis is for standard intervals, for example, from 7 to 19, 19 to 23 and 23 to 7 local time in hours, a sound pressure very high in short time subintervals greatly influences the equivalent continuous sound level of the long time interval. This situation is unfavourable for a quick assessment, and its interpretation may have significant uncertainty. The time intervals of five, thirty, and sixty minutes are very useful in environmental noise permanent monitoring systems. However, their traditional evaluations are complex to obtain the acoustic impact, the exposure time and noise severity that people receive during a prolonged stay or transit through an area. All tests used measurements from an environmental noise monitoring system over several months.