At an international level it is recognised that urban noise has serious and negative public health impacts. This leading editorial and the special issue it accompanies seeks to broaden this agenda. An important goal for Cities & Health is to give ear to new urban health topics, methods and collaborations. In doing so this paper presents the topic of urban sound and health from several unique angles. At its core, we deliberately move the focus beyond noise levels, as measured by decibels, and harm to health through the stress of relentless background noise. Instead, we focus on the concept of soundscape, a more qualitatively nuanced research subject of enquiry. The paper serves as an introduction to soundscape and health from several distinct disciplinary positions and lays a good intellectual foundation for the twenty-two papers published in this special issue. We hope that through a soundscape approach we can encourage fresh thinking about urban sound, including how people perceive and relate to their sonic environments, and show how sound can contribute to health. We believe that this approach can provide a collaborative platform for sound artists, sound technologists, urbanists and local people to work together with public health and create healthier urban environments.

There is plenty of proof that environmental noise is a major pollutant in the urban environment. Several approaches were successfully applied for its calculation, visualization, prediction and mitigation. The goal of all strategy plans regards its reduction and the creation of quietness. This study aims to revisit the concept of quietness in the urban environment and attempts to portray a new understanding of the specific phenomena. “Quietness” as a term retains an ambiguity, and so far, it can be described as the lack of something, meaning the lack of noise that is portrayed by means of intensity. Several studies describe quietness as the combination of perceptual soundscape elements and contextual factors that can be quantified, combined, weighed and used as indicators of healthy soundscapes. In this research, the focus is on setting aside all indicators, either measuring the intensity or contextual ones and use solely quantifiable metrics regarding the acoustic environment, thus introducing a new composite index called the composite urban quietness index (CUQI). After testing the CUQI, in order to verify the results of previous research regarding the identification of quiet Areas in the city of Mytilene (Lesbos Island, Greece), the study concludes that CUQI is efficiently functioning even in this early stage of development.

The degree of functional and structural connectivity of landscapes is a critical issue that could be associated with numerous ecological processes at various scales, in rural and urban environments. The purpose of this research is to evaluate the ecological connectivity of two quiet areas in the city of Mytilene (Greece), using the DPSIR (Driving force–Pressure–State–Impact–Response) framework, which focuses on the description of environmental problems. The application of the DPSIR framework provided feedback regarding the urban acoustic environment of the two quiet areas. Two maps were created with the purpose of assessing impact of road traffic noise on the two quiet areas: a noise map, using the CadnaA software and an acoustic complexity map using the free open source QGiS software. The noise level measurements and the Acoustic Complexity Index were statistically analyzed. The results showed a strong negative correlation due to background traffic noise, diminishing the complexity of the acoustic environment. Furthermore, the results are exploited to develop plans addressing the structural and functional connection of Mytilene’s quiet areas. In conclusion, recommendations are provided so as to preserve urban quiet areas, promoting ecological connectivity and limiting the negative effects of noise on human health and the environment.

“Smart city”, driven by digital technology is not only a technological but also a social, cultural and political project. A socially and culturally significant new urban ideal is born. This research paper is based on the narrative that the city appears as a palimpsest of interventions of all natures. History and shared memory, composition and superimposition, coherence and divergence are fundamental for its evolution. It is thus evident that ”Smart city” as a rather new urban ideal, but also as a disruptive innovation process, cannot be conceived nor implemented all at once; it must follow analogous processes of buildup and stratification. On the other hand, sounds are part of cities, of their sensory landscape, of their identity. They are one of the urban markers, along with the visual landscape. In this context, the paper focuses on the sound identity of the inner-city areas of the Mediterranean metropolis, posing the following research question: What are the transformations that “Smart city” can cause to the sound identity of a city? In dense urban fabric with high-rise buildings, high rates of exploitation, frequent transgressions of the legal construction and least free space in private plots, what can be the prospects of using “smart transport”, for enriching the city with positive soundscapes, thus improving its environmental quality? Following the metaphor of urban and acoustic palimpsest, we examine narratives of replacement of conventional cars with autonomous vehicles (AVs) and of private cars with car-pooling systems. The article concludes that spatialized intelligence can substantially and positively transform the sound identity of the Mediterranean metropolis and be the spearhead for an increase in bio-cultural sonic diversity. At least during the era when the city still appears as a palimpsest of interpositions, evoking the historic time.

In recent decades, climate change has significantly influenced the frequency and intensity of wildfires across Mediterranean pine forests. The loss of forest cover can bring long-term ecological changes that impact the overall biodiversity and alter species composition. Understanding the long-term impact of wildfires requires effective and cost-efficient methods for monitoring the postfire ecosystem dynamics. Passive acoustic monitoring (PAM) has been increasingly used to monitor the biodiversity of vocal species at large spatial and temporal scales. Using acoustic indices, where the biodiversity of an area is inferred from the overall structure of the soundscape, rather than the more labor-intensive identification of individual species, has yielded mixed results, emphasizing the importance of testing their efficacy at the regional level. In this study, we examined whether widely used acoustic indicators were effective at capturing changes in the avifauna diversity in Pinus halepensis forest stands with different fire burning histories (burnt in 2001, 2009, and 2018 and unburnt for >20 years) on the Sithonia Peninsula, Greece. We recorded the soundscape of each stand using two–three sensors across 11 days of each season from March 2022 to January 2023. We calculated for each site and season the following five acoustic indices: the Acoustic Complexity Index (ACI), Acoustic Diversity Index (ADI), Acoustic Evenness Index (AEI), Normalized Difference Soundscape Index (NDSI), and Bioacoustic Index (BI). Each acoustic index was then assessed in terms of its efficacy at predicting the local avifauna diversity, as estimated via two proxies—the species richness (SR) and the Shannon Diversity Index (SDI) of vocal bird calls. Both the SR and SDI were calculated by having an expert review the species identification of calls detected within the same acoustic dataset by the BirdNET convolutional neural network algorithm. A total of 53 bird species were identified. Our analysis shows that the BI and NDSI have the highest potential for monitoring the postfire biodiversity dynamics in Mediterranean pine forests. We propose the development of regional-scale acoustic observatories at pine and other fire-prone Mediterranean habitats, which will further improve our understanding of how to make the best use of acoustic indices as a tool for rapid biodiversity assessments.

The circular economy paradigm can be beneficial for urban sustainability by eliminating waste and pollution, by circulating products and materials and by regenerating nature. Furthermore, under an urban circular development scheme, environmental noise can be designed out. The current noise control policies and actions, undertaken at a source–medium–receiver level, present a linearity with minimum sustainability co-benefits. A circular approach in noise control strategies and in soundscape design could offer numerous ecologically related co-benefits. The global literature documenting the advantages of the implementation of circular economy in cities has highlighted noise mitigation as a given benefit. Research involving circular economy actions such as urban green infrastructure, green walls, sustainable mobility systems and electro-mobility has acknowledged reduced noise levels as a major circularity outcome. In this research paper, we highlight the necessity of a circularity and bioeconomy approach in noise control. To this end, a preliminary experimental noise modeling study was conducted to showcase the acoustic benefits of green walls and electric vehicles in a medium-sized urban area of a Mediterranean island. The results indicate a noise level reduction at 4 dB(A) when simulating the introduction of urban circular development actions.