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The procedure for spatial sampling in order to find out the relation between L(day) and L(night) for urban noise is presented. From that data, other parameters like L(dn) or L(den) can be easily obtained from L(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 L(day)-L(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 L(day)-L(night), with a confidence level of 95% and a margin of error of +/- 1 dB(A).

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Barriers are increasingly used to protect the pedestrian and neighboring buildings from construction noise activities. This study aims to investigate the suitability of applying active noise control on barriers in a construction site to protect the street area and neighboring buildings. Transducers that are simulated in this work are close to the barrier, and their optimal positions are defined in such a way that the control system has the maximum performance at the neighboring areas close to the construction sites. To begin with, the suitable location of the control sources is found when the total squared pressure is minimized at the positions of noise receivers. The suitable location of the error sensors is, then, found when the control sources are fixed at the position of the previous step and the total squared pressure is minimized at the error sensors. The best location for the error sensors is defined when the maximum reduction is achieved in the target area. It is observed that suitable positions for the transducers depend on the location of target areas for noise control, the position of the noise source, and its operating frequency. In this investigation, a unique configuration is proposed for the transducers that achieves a comparable reduction both at the street area and the neighboring buildings, simultaneously. The results show that the active noise barrier with a height of 2.5 m can achieve an extra insertion loss in the street zone, varies from 9.3 to 16.4 dB (in comparison with passive noise barrier) when the distance of the noise source from the barrier changes in the range of 7 to 1 m, respectively. Those values are of the same order for the passive noise attenuation. Furthermore, similar results are achieved when attempting to cancel the shadow zone of a façade 15 m away from the barrier.

This paper proposes a temporal sampling strategy that increases the accuracy of long-term noise level estimation and allows to establish the estimation error according to the number of sampled days. Days of the week are stratified into working days and weekend days. This research shows how to use measurements of L on working days to estimate the corresponding values for weekend days. This is possible because working days have higher noise levels and less variability than weekend days. The improvement in accuracy allows for a reduction in the number of required sampled days compared to taking samples randomly, which would help to reduce the uncertainty in environmental noise assessment. As a reference, to obtain a 90% confidence interval of ±1 dB for L, the proposed sampling strategy reduces the required measurement days by more than 38%. For L, the reduction is close to 18% of the total number of days. The proposed strategy could be adapted to different environments by simply changing a few parameters.