Our interpretation of the world is mediated through a variety of mechanisms that have been at the center of architectural and urban debate for a long time; the role of hearing in perceiving and recognizing the surrounding environment is fundamental and of growing scientific interest. Studies that investigate the psychological effects of noise produced by large infrastructures, such as airports, highways, railways, are multiplying. Santiago Beckdorf argues that it is possible, through the tools of design, to reverse the paradigm according to which urban development is inevitably connected to a weakening of the natural environment in which it is inserted.
For the 2019 Shenzhen Biennale of Urbanism\Architecture (UABB), titled "Urban Interactions," (21 December 2019-8 March 2020) ArchDaily is working with the curators of the "Eyes of the City" section to stimulate a discussion on how new technologies might impact architecture and urban life. The contribution below is part of a series of scientific essays selected through the “Eyes of the City” call for papers, launched in preparation of the exhibitions: international scholars were asked to send their reflection in reaction to the statement by the curators Carlo Ratti Associati, Politecnico di Torino and SCUT, which you can read here.
¿How to produce, through acoustic manipulation, a mutualistic relationship between humans and animals under the erosion process that natural environment is suffering because of urban sprawl?
Sound is one of the most relevant senses that many living species posses, in order to build a better perception of the world. 
Living beings dispose of many different methods to build their own experience of the world. Whatever the medium is, they have mechanisms to scan space and interact with the environment and other living beings. Some species have developed a sharp sense of sight, which enables them to detect their prey from considerable distances or even in poor light conditions There are animals, such as whales and bats, that use echolocation as a mechanism of spatial decoding, through the emission of high frequency “clicks” which travel across different mediums and after bouncing back because of physical obstructions, they allow to build a three-dimensional space with fantastic accuracy. Hence, as Steven Connor declares: ‘Sound has the capacity to disintegrate and reconfigure space’ (Gandi 2014; p09).
Even though human with the sense of sight, have a perception of the world based on space and distance, sound plays an essential role in the quality of that spatiotemporal experience. So, when an acoustic condition has a special meaning on the definition of a specific space, we talk about soundscapes. (Fig. 1)
Change of Perception; Antrophogenic Soundscapes
The story of soundscapes is tightly bounded with human history. In the past century, acoustic environments have changed dramatically. So, to have a better understanding of the evolution of soundscapes, there is a distinction between rural (Hi-Fi) and urban (Lo-Fi) soundscapes.  On the one hand, rural landscapes allow having a more precise and further acoustic perception because of the absence of ambient noise.  On the other, urban soundscape is made by a complex juxtaposition of sound sources, which produce a diffuse acoustic perception that makes it hard to identify specific sounds that are highly valued. 
The explanation of soundscape decay is associated with the ongoing geological and anthropological era: the Anthropocene. Furthermore, it is not just about cities. Rural areas present high levels of sound pollution because of the irruption of urban infrastructures such as highways, railways and airports, but also; industries, farming activities, forestry and many other human productive activities that add significant levels of ambient noise across nature environment.
Consequently, it is relevant to do a bit of research about the positive and negative impacts that specific kind of sounds has over different players within the build and natural environment.
Sound effects over human and animals
Anthropogenic soundscapes it is not just an environmental issue, but a matter of government concern, it is also a threat to human health, education and productivity. 
For instance, the World Health Organization (WHO) defined six major cities in Europe where noise pollution is ranked at the second place of environmental stressors. Furthermore, living within noisy environments produce not only an uncomfortable feeling but, there are physiological consequences over living beings such as stress, hypertension, sleep and concentration distortion, among others. 
In this chapter will be necessary to isolate individual acoustic perception.  That means that a specific sound could be enjoyable for someone, but, it does not mean it will be for others. Now we deepen into the proven field of science. To understand a bit more about how sound, affect living beings, it is necessary to divide it into two main components; Decibels (dB) and Frequency (Hz). Decibels are the nomination of a specific amount of energy/pressure that a sound wave has, saying simply, is a degree of loudness.
Meanwhile, frequency is the measurement of the wavelength, that defines the range of hearing according to different tones. A shorter wavelength will be perceived as a high-frequency sound, such as birds singing. In the opposite case of a long wavelength, the result will be a lower pitch such as wind blowing or the general perception of urban sound.
Both decibels and frequency are relevant when analysing the impacts that sound have on different species. There is one example that shows significant evidence of how living close to noisy environments produces a decay on life quality. The Lancet Journal of Medicine, published in 2005 RANCH (Road traffic and Aircraft noise exposure and children’s cognition and health), an investigation that showed that kids attending to schools close to airports, struggle more than kids studying in quiet areas. 
As our cities continue to grow, noisy infrastructures located at peri-urban areas, such as airports, highways, railways and industries, are going to be surrounded by residential clusters of low-density housing (Fig. 2). As most people have a negative perception of living close to any of the mentioned infrastructures, urban sprawl is eroding natural habitats of several animals, obstructing ecological corridors that keep the balance of urban ecosystems. Consequently, species like birds and bats, which are potential pollinators, are highly sensitive to urban noise, which affects their mating and birthing rates. 
Shaping Soundscapes aims to revert the degradation trend of the peri-urban acoustic environment, understanding the rapid urbanization process as an opportunity rather than as a problem. Due to that, it is necessary to shift the paradigm of co-inhabiting with noisy infrastructures, towards the protection of natural soundscapes, therefore improving biodiversity and the mutualistic relationship between humans and animals. 
An interesting quality about sound as a design driver is that can be tackled at different scales and through multiple approaches. Nowadays, the focus is on working with indoor acoustics rather than outdoor. Achieving “acoustic comfort” through the absence of sound, rather than tunning better soundscapes taking advantage of nature as a positive sound source.
The goal of this research is to develop a methodology through which could be possible to revert the negative acoustic quality of some places due to their relationships with urban infrastructures. Starting from urban planning scale, setting new criteria for the location of the future urban developments and the preservation of natural environments. Secondly, urban design scale; defining new typologies for the urban fabric and landscape topography, in order to have a better performance dealing with un-wanted sounds and, enhancing positive sounds coming from natural areas. Finally, the micro-scale of materials and architectural design, considering material density as a key variable for the acoustic manipulation of sounds.
Simulation process; acoustic behaviour
Beyond theory, was necessary to went through digital (Fig. 3.1) and physical (Fig. 3.2) simulations to get a better understanding of sound behaviour under several conditions and, set the parameters to build up a predictive model that was used for testing different topographic and urban typology design proposals, as well as material density sound absorption at different frequency bands.
The methodology was tested on a specific site within the London GreenBelt. The aim was to collect precise data on-site about sound decibels and frequency, considering that the site was very close to a significant highway coming from central London, but on the other hand, there was a public park with a wetland and a forest with a broad range of birds. So, it has all the ingredients to test the design guideline and through an urban development proposal, to rebalance the current soundscape, harmed by traffic noise and enhance natural sounds from the park.
Urban Infrastructures and Natural Systems; Urban Planning scale
Designing with acoustics at the urban planning scale does not seem to be a traditional approach. However, understanding the impact that urban processes produce over the landscape and the natural systems within it is a relevant aspect to consider when planning urban development. Even though urban infrastructures such as airports and highways or railways, consider acoustic mitigation structures, there is not a clear position regarding how to deal with those noisy areas through a new definition of land use, density and urban form.
The case of the London GreenBelt, as an urban sprawl constrain policy (Fig. 3.4), is an excellent example of how, on the one hand, transportation network (Fig. 3.5) provides connectivity and enables people to have proper access to goods and services, but on the other hand, produce a fragmented soundscape (Fig. 3.6). Natural environments, such as parks, areas of outstanding natural beauty (AONB), sports fields and farming lands, are interrupted by a dense network of highways, motorways and railways. Besides the four international airports surrounding London, located within the GreenBelt.
As mentioned before, the transportation network is not the place where people prefer to live close to, because of the noise they produce. In fact, cheaper houses are the one closer to this noisy spots, not only because of noise but the vibration that affects the infrastructures and produce adverse effects over people health.
The first strategy is to shift the paradigm. Dwell close to a railway or a highway is not bad at all understanding the potential implicit in these places. Not only because of the connectivity but also because they represent natural migration paths and habitats for many species of birds, small mammals and rodents.
Secondly, an essential piece of evidence of the simulation process was the effectiveness of physical obstructions to reduce sound spreading. Due to that, the densification along the roads or railways (Fig. 3.7) would reduce significantly the acoustic impact of these infrastructures over natural soundscapes, preserving acceptable ranges of sound that allow species to have proper communication.
Therefore, the sound could be a valuable input towards decision making at city scale as long as we are able to see the big picture of the interactions that exist between urban areas and natural systems.
Urban Typology, Topography and Ecology; Urban Design scale
From the understanding of sound behaviour through the simulation process (Fig. 4.1), as mentioned before, buildings are highly effective in reducing sound spreading. However, they produce other un-wanted sound phenomena such as echo or reverberation. So, to increase effectiveness without secondary effects is suitable to apply multiple criteria to ensure acoustic comfort.
There are two main strategies to work with sound tunning spaces; mitigating unwanted sounds and, introducing positive ones (Fig. 4.2).
Therefore, physical obstructions reduce the energy of the sound wave in each bounce and produce diversion of sound. From here, there are variables that increase sound refraction, such as the density of the elements. For instance, the same effect rules over trees and buildings but is undeniable that buildings are more effective than trees reducing sound spreading. Nevertheless, and because of their different composition, trees can modify the perception of sound because they reduce certain frequency bands depending on their canopy density. So, they could be less effective in reducing sound spreading, but they can be used to tackle some pitches and to add positive sounds like, for example, birds and leaves when wind blowing. The mentioned phenomenon is considered as sound masking. 
In the case of the demonstration area in the London Greenbelt; the objective was to reduce low-frequency sounds produced by the highway, and to increase natural sounds from wetland and forest. For that reason, the design strategy was grounded on three main decisions dealing between mitigation and sound masking;
a. Green Buffer_
The first intervention was to take distance from the highway. This decision follows two main ideas; protect animal species using roads and railways as migration corridors and generate a public space where through topographical and ecological interventions could be possible to produce a significant reduction of the traffic noise perception in the residential area. (Fig. 4.3)
Sound travels through different mediums following the basis of waves. Every obstruction is going to change the direction of the sound wave. In the case of the ground floor, it has significant importance regarding sound absorption. So, applying vegetation, grooved surfaces made by porous materials and adding earthworks to produce artificial topographies is an effective way of dealing with sound from the highway.  (Fig. 4.4)
For instance, Buitenschot Park, located next to Amsterdam Schipol Airport is an excellent example of how to reduce low-frequency sounds produced by taking off aircraft by using 3 meters high embankments creating a lattice in the whole area that reduced 10 dB the ground floor sound perception. (Fig. 4.5 – 4.6)
So to address the reduction of traffic noise, the proposal includes three hills; the first hill of 3 meters high, hiding the road from the buffer green area and diverting sound, then a 2 meters high hill to define the green safe corridor for different species dwelling close to the highway. Finally, a 1-meter high hill close to the first line of buildings.
In addition to the topographic intervention, the introduction of specific kinds of vegetation increased sound absorption rates, especially low-frequency sound, produce sound masking effect by wind blow tree leaf and, increase birds singing.
- Vegetation_ In the first hill facing the road, the trees species should be evergreen trees to keep the absorbing effect even in autumn and winter. Besides, they should have dense canopies, so coniferous trees, such as cypress or pines are the most appropriate. In addition, shrubs are highly effective because they fill the gap produced between the trunks under the canopies. Also, they are a good shelter for small mammals, rodents or reptiles (Fig. 4.7).
- Birds_ Introducing specific bird species according to their mating, birthing and community living patterns is another way of re-balance soundscapes. Due to that, is critical to work with species with peaceful pitches, and looking for mutualistic relationships and avoiding predators that could destroy the ecosystem balance (Fig. 4.8).
Morphology and Material density; Architecture Scale
Braking down the scale into the architecture field, there are two main variables that define sound behavior; morphology and material density.
Between the 1916’s and 1930’s in the south and northeast coast of England, several pieces of concrete were built as radar forerunners. These concave concrete structures focalize sound from aircraft flying further than 20 miles across the channel, into microphones that detect any movement in the sky (Fig. 4.9).
Morphology is about manipulating sound through divergence and convergence of waves, produced by the bouncing of sound on different kinds of surfaces (Fig. 4.10). From here, is possible to consider sound as a design driver within the architecture practice, not only to produce negative sound diffusion but to enhance and amplify positive ones. It could also be understood as the topography of building facades, as well as isolated structures such as sound mirrors, that instead of finding war aircraft, are focalizing bird singing, the wind blowing, or water sound.
Furthermore, to make sure that sound mirrors were accurate detecting sound, it was crucial to add another variable to the equation; material density. The value that defines density is the amount of air contained in a specific material (Fig. 4.11). The more air a material has, the better absorption capacity it will have and, at the opposite, the less air contained, better reflective capacity. That is why sound mirrors were built with dense concrete and taking special care in the final layer, it should be as smooth as possible, with the less amount of porous on its surface.
However, morphology and density are not just about the vectorial behaviour of sound. They also can be used to tackle some specific frequency band that could be harmful to humans and animals. There is a direct relation between the diameter of the pores and the frequency band they are targeting. Hence, collecting precise spatiotemporal data allows defining some material and building standards to ensure high levels of absorption of sounds that could produce adverse effects over infrastructure and living species.
Nowadays, we have access to technology that makes it possible to collect precise information in real-time. What we do with that information is one of the challenges that we face as designers. Light has been, from the beginning of architecture history, the most relevant design variable. However, it is important to pay attention to other senses that make it possible to build a different understanding of the world, and sound is, not only for blind people but for every living species, an opportunity to redefine our spatial and emotional environment.
Architecture has been travelling for this path for a long since masterpieces such as Epidaurus Theatre in the Greek culture, Le Corbusier and Iannis Xenakis with the Phillips Pavillion and recently the broad range of materials and devices to produce quiet spaces. Nevertheless, noise pollution is a matter of human health and ecological balance, that must be addressed through other disciplines such as urban planning, urban design, landscape architecture, ecology and geography.
This research target in that direction, aiming to bring together multiple backgrounds and applying technology that allows us to develop not only exciting projects but to move forward to new regulations that make possible to preserve natural and urban environments from noise pollution.
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About the Author:
Santiago Beckdorf is a Chilean architect from UDD School of Architecture (2012), and March in Urban Design at The Bartlett School of Architecture, University College London (2018). Since 2013 he has been a lecturer at UDD School of Architecture at the Architectural and Urban Design Studios. He is a fellow researcher at UDD Innovation City Centre, an applied research laboratory committed to developing collaborative methodologies through a theoretical and practical approach towards urban design solutions with a strong focus on smart cities and big data. Currently, he is part of the urban design experts committee for the project “Chile Lagos Limpios”, an initiative to propose strategic guidelines for sustainable management for the principal watersheds in southern Chile, supported by UC David’s and Lake Tahoe Foundation.
Opening in December, 2019 in Shenzhen, China, "Urban Interactions" is the 8th edition of the Bi-City Biennale of Urbanism\Architecture (UABB). The exhibition consists of two sections, namely “Eyes of the City” and “Ascending City”, which will explore the evolving relationship between urban space and technological innovation from different perspectives. The “Eyes of the City" section features MIT professor and architect Carlo Ratti as Chief Curator and Politecnico di Torino-South China University of Technology as Academic Curator. The "Ascending City" section features Chinese academician Meng Jianmin and Italian art critic Fabio Cavallucci as Chief Curators.
"Eyes of The City" section
Chief Curator: Carlo Ratti.
Academic Curator: South China-Torino Lab (Politecnico di Torino - Michele Bonino; South China University of Technology - Sun Yimin)
Executive Curators: Daniele Belleri [CRA], Edoardo Bruno, Xu Haohao
Curator of the GBA Academy: Politecnico di Milano (Adalberto Del Bo)
"Ascending City" section
Chief Curators: Meng Jianmin, Fabio Cavallucci
Co-Curator: Science and Human Imagination Center of Southern University of Science and Technology (Wu Yan)
Executive Curators: Chen Qiufan, Manuela Lietti, Wang Kuan, Zhang Li