Spatial sampling for night levels estimation in urban environments

Abstract

The procedure for spatial sampling in order to find out the relation between ${\mathrm{L}}_{\mathrm{day}}$ and ${\mathrm{L}}_{\mathrm{night}}$ for urban noise is presented. From that data, other parameters like ${\mathrm{L}}_{\mathrm{dn}}$ or ${\mathrm{L}}_{\mathrm{den}}$ can be easily obtained from ${\mathrm{L}}_{\mathrm{day}}$ values. To this end, a long-term measuring campaign was carried out in eight cities of different types and sizes in northeastern Spain. The statistical treatment of the measures was based on a characterization of the streets in view of their type, including factors such as traffic and land use, which enabled a final classification of six types of streets. The results show that streets of the same type located in different cities do not have the same value for ${\mathrm{L}}_{\mathrm{day}}$ -${\mathrm{L}}_{\mathrm{night}}$ , due to socioeconomic factors, but analyzed city by city have a close to normal (or $t$ -Student) distribution. Under this behavior, it is demonstrated that a sample of between 14 and 25 points, depending on the city characteristics, is needed in order to calculate ${\mathrm{L}}_{\mathrm{day}}$ -${\mathrm{L}}_{\mathrm{night}}$ , with a confidence level of 95% and a margin of error of $\pm 1\mathrm{dB}\left(\mathrm{A}\right)$ .