The "sound of silence" in Granada during the COVID-19 lockdown

Exceptional circumstances in the city of Granada due to the COVID-19 lockdown have provided the opportunity to characterise the impact of humans on its urban acoustic climate. Traditional environmental noise management and urban sound planning usually take into account noise sources in the city, such as industrial activities or road traffic noise, in model estimations, as well as in empirical research. But trying to isolate human impact by itself, human activity including social activity, walking, talking or just going around the city, has always been a difficult or even impossible task. The COVID-19 lockdown measures have provided the opportunity to study urban climate as never before, affected just by natural or animal noise sources. Previous soundscape research at some iconic sites in the city of Granada carried out in 2019 before the lockdown and a special measuring campaign carried out at the same locations during the lockdown in 2020 offered valuable information on sound levels and local characteristics in order to carry out this comparison. Results show a great change in environmental noise levels that is interesting not only because of its magnitude, but also for its implications, especially at those sites where social human activity was an identifying characteristic. Natural or animal sounds became surprisingly evident at some study sites, especially where road traffic noise dramatically decreased, leading to significantly lower background noise levels. Important spectral changes are observed before and during the lockdown, suggesting a shift from anthropic to animal sources in the acoustic environment.