Noise hindering sound complexity in urban environments: Towards a novel evaluation criterion for urban sustainability

Urban environments are complex adaptive systems, wherein changes in one area can lead to unforeseen consequences in others. Environmental noise emerges as a multifaced issue influencing various receivers across different spatial and temporal scales. The perception of noise as a high-intensity or unwanted sound has defined the concept of quietness accordingly overlooking sustainability co-benefits. This study proposes an alternative evaluation criterion for urban planning and design, focusing on the sound complexity of public spaces that are vulnerable to environmental noise fluctuations. To determine the sensitivity of sound complexity to environmental noise, sound level measurements and sound recordings were conducted along the waterfront of a Mediterranean metropolis during the pandemic lockdowns (April 2021). Additionally, the bird dawn chorus phenomenon was studied. The analysis of collected data revealed an inverse relationship between complexity and noise, highlighting an additional impact on the urban sound environment. The promotion of sound complexity as a strategy for livable and sustainable cities can guide urban planners and designers in developing quiet and ecologically resilient urban environments.