# Suitability of Active Noise Barriers for Construction Sites
## 6 Conclusions  
Successful implementation of an active noise barrier close to a construction site requires an effective configuration for the control devices and a good understanding of different scenarios for a moving noise source. The main contribution of this work is studying the suitability of an active noise barrier to control the construction noise activities in the neighboring street area and the nearby building facade for a noise source in the construction site. The noise source is represented by a point source placed at different positions regarding the barrier (as a mobile source would do) and operates with the typical sound spectra of construction noises. Although a single optimal configuration is found that gives the maximum attenuation for any plant configuration, results suggest that there is a suitable broad region for locating the transducers with quite similar results of attenuation for most of the different plant conditions (in this study, the distance between the noise source and the barrier and the position of the cancellation target zone). The suitable region for the control sources is whatever position below the line that connects the noise source to the edge of the barrier and as far as possible from the barrier (0.5 m in this study). The region for the error sensors also is whatever position in the diffracted field of the shadow zone and as possible from the barrier (0.5 m in this study), which is below the line between the edge of the barrier and the farthest receiver. Whatever configuration that follows these rules and for the number of sources and error sensors considered in this study, good attenuation results are yielded in the whole shadow zone behind the array of the error sensors, as cancellation at any of the two target areas has always achieved good attenuation in the other zones. It is shown that with the geometry of this study for the target zones, when the noise source is 7 m far away from the barrier, the passive attenuation of the barrier reduces the noise level to 11.4 and 9.1 dB in the street area and in shadow zone of the facade, respectively. Besides, the active cancellation with the optimized configuration for the control transducers when the shadow zone of the facade is the target area can increase the noise mitigation level to 20.3 and 17.4 dB in the street area and the shadow zone of the facade, respectively. An implication of these results is the expandability of the implementation of the active noise barrier to control broad cases of construction noise scenarios. Figure 7: Insertion loss at the observational points in the shadow zone of facade, \(\overline{IL}_{FS}\) (dB), when (**a**) street area ((\(X_{s}\), \(Z_{s}\)) = (\(-\)0.5, 1.8), (\(X_{e}\), \(Z_{e}\))= (0.4,0.2)) and (**b**) shadow zone on the facade((\(X_{s}\), \(Z_{s}\)) = (\(-\)0.5, 2.3), (\(X_{e}\), \(Z_{e}\)) = (0.3,0.4)) are the target areas. As an additional criterion, the barrier should be placed as close as possible to the noise source, to reduce the risk of raising the noise level in the top part of the building. However, the overall performance of the proposed configuration is also relatively independent of the position of the noise source, as the attenuation in the shadow zone of the barrier remains almost unchanged for distances between the noise source and the barrier between 2.5 and 7 m.  
Conceptualization, S.S., T.P.G. and J.R.G. ; methodology, S.S., T.P.G. and J.R.G. ; code developing, S.S.; formal analysis, S.S., T.P.G. and J.R.G. ; investigation, S.S., T.P.G. and J.R.G. ; writing--original draft preparation, S.S.; writing--review and editing, T.P.G. and J.R.G. ; visualization, S.S.; supervision, T.P.G. and J.R.G. All authors have read and agreed to the published version of the manuscript. This research was funded by a grant from Agencia de Gestio d'Ajuts Universitaris i de Recerca, grant number is 2020 FI_B2 00073. This research was financially supported by Agencia de Gestio d'Ajuts Universitaris i de Recerca (AGAUR) from Generalitat de Catalunya. [PERSON].