In the shadow of climate change, there's a subject that gets far less media coverage than global warming, but which could make a big splash. It's the state of sound on our planet, and in particular in the living world. There is no such thing as silence on Earth; noise is constantly being heard.
Sometimes a source of annoyance, noise is above all a vector of information as surprising as it is varied. Birds singing, waves lapping, leaves rustling... nothing new under the sun, and yet!
The development of Bioacoustics, initiated by Bernie Krause in the 1960s, has enabled us to identify the acoustic activity of thousands of animal species.
In addition to this wealth of animal sounds, his work and that of his successors has shown the extent to which human activities have damaged existing ecosystems.
Conceptualized among others by M. Schafer and B. Krause, the notion of "soundscape " encompasses both sounds originating from abiotic elements, i.e. any element not attributed to a living being, such as the wind (geophony), sound activities of human origin (anthropophony) and sounds specific to flora and fauna (biophony).
The term "Anthropocene" was coined in 2000 by American biologist Eugène F. Stoermer and chemist Josef Crutzen. Stoermer and chemist Josef Crutzen first referred to the Anthropocene as a new geological phase that would appear with the onset of the industrial revolution in the 19th century. For almost 12,000 years, mankind as we know it had been evolving in the Holocene epoch, and was acoustically part of a category nested within biophony: Anthropophony (sounds of human origin).
With the advent of man, the place of geophony and biophony in the soundscape has changed. Biophony is already particularly rich, with a multitude of vocalizing living organisms. According to Q. Arnoux in his book Ecouter l'Anthropocène, " the initial relationship that human beings develop with soundscapes is one of adaptation, listening and inspiration ".
Krause described the acoustic links between the sonic emergence of the human species and existing soundscapes as: " The elaborate interactive process by which each animal voice found an available frequency or time slot certainly did not escape the methodical minds of our ancestors. It must have served as a model from which to arrange our own sounds, to form our voice and our first instruments ".
Each vocalizing species (including Man) shares a very broad sound spectrum, far more extensive than the performance of the human ear. However, as part of our evolution, we began to create new sounds, no longer resulting from our own vocalization through a system of onomatopoeia, as described by B. Krause, but from our own activity in the broadest sense. As language and music become an acoustic identification specific to human beings, anthropophony becomes an integral part of the earth's soundscape.
With the onset of the Industrial Age and the constant modernist growth of Western civilizations, sounds of mechanical origin are increasingly present on Earth. This new acoustic production is not just another component in the soundscape, it is also imposing itself through its intensity and duration, masking many acoustic layers. The appearance of this new acoustic layer, often described as "noise pollution", is called Technophony. Airplanes, trains, industry, mechanical tools, etc. form a layer of sound that encroaches on both Biophony and Anthropophony as man's industrial growth proceeds.
For only a few years now, noise pollution issues have been taken into account in measures to protect the population. But these considerations are only an anthropocentric vision of noise pollution; all living beings are impacted by noise pollution through multiple effects.
Noise pollution, particularly its intensity, causes species present in an exposed environment to flee. When species don't flee, they have to adapt to a new soundscape.
Take the example of passerines exposed to high levels of road traffic noise: to survive in this environment, they will have to increase the volume of their vocalizations and the associated emission periods.
The consequence of this forced adaptation is an additional expenditure of energy by the passerine, leading to premature exhaustion and consequently an accelerated decline in the population in the environment.
From an acoustic point of view, human activities do not only emit frequencies audible to humans: submarine sonar emits ultrasound, disrupting the communication of some cetaceans; road traffic noise impacts a large number of species over a wide spectrum, also audible to humans; drilling activities emit numerous infrasounds, etc...
So pollution is the business of every living thing!
The study of biodiversity through the prism of sound is often referred to as bioacoustics. But there's more to it than that, and we need to distinguish between two notions: bioacoustics and eco-acoustics.
Bioacoustics, which has its origins in the first recordings of birds made by L.K. Koch in the late 19th century, studies the sound behavior of animal species, otherwise known as biophony. It focuses primarily on the study of recorded sound signals from animal species, in order to decipher behavioral and social information about wildlife. This discipline has developed at the same pace as technological resources, particularly computer technology.
The study of sound signals requires numerous resources and material capacities: microphones, storage, computing power, etc... This discipline focuses exclusively on the study of an animal's sound signature and the information that the sound signal conveys. It studies the sound mechanisms specific to different living organisms, in particular their resilience and the adaptation of species to changing environmental conditions, including climate change.
Eco-acoustics is a much more recent discipline, initiated mainly by the work of Bernie Krause. Unlike bioacoustics, which focuses on the individual study of a species, eco-acoustics takes a much more macroscopic view, recording and analyzing the sound activity of a biome.
By performing a sonogram of an ecosystem recording, we can analyze the acoustic signature of the different species present in the environment. This method, previously performed empirically, can now be "automated" using machine learning tools to identify all the species present in one (or more) recording(s).
Eco-acoustics therefore considers sound as an integral component of the characteristics of an environment, making it a de facto environmental indicator for monitoring biodiversity.
In our collective consciousness, we see climate change through the prism of vision alone: the sea ice is melting, floods are becoming more and more frequent, storms are increasingly devastating, and so on.
But would climate change and the erosion of biodiversity also be audible? This is where eco-acoustics comes into its own.
The main aim of this discipline is to characterize the sound richness of an environment, not at the level of the individual, but of a species or even a group of species.
Today's technologies enable us to capture a sound spectrum much wider than human hearing, and to acquire tens of thousands of hours of recordings. All this information must then be analyzed, in particular using automatic sound recognition to identify the species present and their numbers.
Traditionally, ecologists carry out an inventory of animals on a given site once or twice a year, providing little information on the behavior of species and their interactions during the day. The information gathered by recordings can also be used to observe the impact of certain disturbances (particularly human disturbances) on an environment.
The impact of man-made noise is even becoming a physical factor in " ecological fragmentation ", which can decimate entire populations close to sources of noise, particularly overland transport routes.
A better assessment and analysis of these soundscape modification phenomena would be useful for nature conservation strategies.
Following the example of green and blue grids in urban environments, the Paris Institute of Ecology and the Environment has proposed white grids to form silent ecological continuities and combat the conquest of noise; the French Ministry of Ecology and Solidarity has also published a methodological guide to combating underwater noise; the identification and preservation of quiet zones is part of the Environmental Noise Prevention Plan (PPBE ); and many other initiatives are taking shape.
A gentle awakening seems to be well underway when it comes to noise pollution, both for humans and for all living beings.
The confinement of the spring of 2020 has shown us particularly well, if silence seems to be settling in by lowering our noise pollution, nature manages to express itself more beautifully.
The challenges of our future soundscapes have yet to be perfected, but reducing our emissions of pollutants, particularly noise, is one way of redefining our landscapes and combating climate change.
Driven primarily by the challenges of sustainable development, low-carbon and societal concerns, wood construction is on the increase in the design of new and renovation programs, whatever the purpose (housing, offices, hotels, cultural facilities). From an acoustic point of view, these new complexes in the French construction landscape raise a number of questions.
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