Inhabitants of Barcelona, as those of other many regions in Europe and the world, suffered a forced lockdown who reduced drastically the economic activity lastest april and may.
The noise sensors Barcelona City Hall had connected to Sentilo offered their logged data publicly and researchers could check what was the noise reduction caused by the lockdown in the city.
During the hardest days of the lockdown, the reported reduction of noise climbed to as much as 10 dB in Barcelona!
You can check the articles published on local newspapers if interested:
El silenci que ens va portar el confinament (in catalan)
The silence that brought us confinement (English Google translated)
Barcelona, in silence: measurements prove a drop in decibel (English Goolgle translated)