Aggelos Tsaligopoulos

Article Rethinking environmental noise assessment through a noise footprint framework was published on January 1, 2025 in the journal Noise Mapping (volume 12, issue 1).

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 concepts of noise and quietness are multidimensional, contradictive and retain a degree of fuzziness. Their notion expands between the physical dimension of sound to a phenomenological/perceptual construct. The perception of noise as a sound of high-intensity or as an unwanted sound has shaped the concept of quietness as an urban sound design goal overlooking ecological co-benefits. The main purpose of this research is to highlight the symbiotic relationship between urban quietness and sustainability. More specifically, actions of circular urban development, including green walls and electromobility were modeled, to highlight their effect on the sound environment of a Mediterranean coastal medium-sized city. Following the guidelines provided by the CNOSSOS-EU road traffic noise model, the effects of the aforementioned sustainability actions were visualized by means of noise mapping. The results indicate that a noise level reduction of approximately 4 dB(A) could derive with the implementation of circular urban development measures.

Public spaces underwent a notable shift in their acoustic profile during the societal restrictions resulting from the COVID-19 pandemic. A silver lining emerged from this global crisis, with noticeable improvements in public acoustic environments due to reduced noise levels resulting from restricted mobility. This research focuses on the acoustic environment of Thessaloniki’s waterfront, a Mediterranean metropolis in Northern Greece. Waterfronts of Mediterranean coastal cities provide unique acoustic environments worthy of protection from environmental noise. By analyzing sound level measurements and recordings during the 2021 lockdown and comparing them to the post-lockdown period in 2022, we aimed to explore environmental noise and acoustic complexity indicators. The study’s findings revealed a significant increase in acoustic complexity during the lockdown, underscoring an inverse relationship between noise levels and acoustic complexity. Urban waterfronts, like Thessaloniki’s, hold great potential for enhancing acoustic complexity and subsequently improving the acoustic quality of public spaces while protecting them from environmental noise. This research sheds light on the possible use of sound complexity as an environmental quality standard that can be incorporated in sustainable urban planning and design.

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.

Drystone terraces offer a series of ecosystem services including both biological and cultural benefits. The aesthetic contribution towards the landscape and the increase in biodiversity levels, constitute drystone terraces and other similar constructions, as important biocultural assets. The low maintenance and the eventual abandonment of drystone terraces cause a series of drawbacks regarding the sustainability of agricultural environments. The main goal of this research was to assess the effect of drystone terrace maintenance level on biodiversity. For that reason, two closely distant agricultural areas of Lesbos Island (North Aegean, Greece) in which olive grove drystone terraces dominate were compared. The non-intrusive method of ecoacoustics was selected, and the levels of the acoustic complexity and acoustic diversity were statistically analyzed for areas that included highly maintained and poorly maintained olive grove drystone terraces. The results indicated an increase in acoustic biodiversity levels in the poorly maintained drystone terraces area. At this early stage, the results highlighted the fact that the increased resources in the poorly maintained drystone terraces, in terms of nesting and feeding opportunities, increased the biodiversity levels. Nevertheless, the spatiotemporal expansion of this research is undeniably important.

Quietness in an urban environment is vital for the well-being of city residents. Nevertheless, the ambiguity in the conceptualization of the terms noise and quietness as urban acoustic planning and design objectives, has resulted in two different approaches: the soundscape approach and the noise control approach. The main purpose of this research is to supplement the existing approaches by proposing a new ecological acoustics approach in order to identify quiet areas in the city of Mytilene (Lesbos Island, North Aegean, Greece). The use of the soundscape approach involved the participation of Mytilene’s residents and the collection of subjective and objective eligibility criteria. By means of Multi-Criteria Decision Making two urban green areas were highlighted as potential quiet areas. For the noise control approach, road noise maps have been created through a commercial noise mapping software, validated by trough measurements. As a result, two areas located in the outskirts of the city were highlighted. Finally, the novel ecological acoustics approach involved acoustic recordings and the extraction of the Composite Urban Quietness Index (CUQI). The outcome of this approach converged with the soundscape approach results. Quietness, as an urban acoustic planning and design goal, could be viewed as an opportunity for ecologically sustainable urban environments.

Sound is an inseparable part of the living environment and the liveability of the city, whilst environmental noise is a major stressor affecting the urban environment. Several approaches have been applied for its mitigation and the goal of several strategy plans regards the creation of quietness. “Quietness” as a term retains an ambiguity and it can be described, so far, as the

“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.