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. 2020 Oct 5;10:16487. doi: 10.1038/s41598-020-73102-3

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© The Author(s) 2020

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

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(a, b, d) Time series of the noise amplitude (in nm) in the frequency band between 5 and 20 Hz as obtained from the PPSD analysis. Red horizontal lines represents the average noise level for each working week. Continuous black vertical line mark the lockdown date (DPCM-1) while the following dashed one refers to the closure of all commercial activities (DPCM-2). Light purple vertical bands highlight the weekend. In (a) in light gray we indicate the reference time window represented by the 2 weeks preceding the lockdown (REFWs) and the following four weeks (W₁–W₄). In (c) we show using blue and orange lines, mobility reduction and NO₂ level respectively as recorded at Milano. In (e) the number of vehicles per hour (blue line) and NO₂ level (orange line) for Firenze are shown. Further details could be found in section “Results”.