Expedite methodology for assessing noise levels in an urban scenario based on a new parameter: the significant measurement starts (SMS)

Abstract

With the new Portuguese Noise Code (and the new European Directive) there is a necessity to develop an expedite methodology to evaluate noise levels at typical urban scenarios, checking for their ability to be reproduced with reliability at urban spaces with similar occupational pattern. In this work, a new urban scenario was studied representing a typical backyard situation in an urban centre, based on continuous measurements of the Short-term LAeq performed during one month. The major goals in this work were: to identify, during each day, the preferred time intervals at which any measurement started during it would achieve, with a pre-determined probability, a significant estimation for the all period LAeq parameter, that is to say, varying within a limited and clearly identified interval relative to the results provided by an integral analysis of noise; to precise the duration of that measurement in order to achieve the referred objective, during daytime and nighttime. The strategy adopted was to idealize a new describer that could be used as a performance evaluation criteria for the chosen time intervals, called the Significant Measurement Starts (SMS). This represents the probability that a single measurement, with a given duration, started in a pre-defined time interval, can provide a significant result. A SMS equal to 0.50 was set as the minimum value from which a time interval could be considered suitable to be held as a preferred time interval to start a measurement. Different conclusions were achieved both for day and night periods and for weekdays and weekend days. The potential uncertainty of performing random measurements was also investigated.