Solidian Soundscapes: Artistic Research on Spatial Quality of Sound in Soil

Solidian Soundscapes: Artistic Research on Spatial Quality of Sound in Soil Paul Goutmann1,2⇤[0009000948890579] and Diane Schuh1,2,3⇤[0000000341556868] 1CICM-MUSIDANSE-Paris 8 University, Saint-Denis, France 2Graduate School ArTeC, Aubervilliers, France 3UMR STMS 9912 (CNRS-IRCAM-Sorbonne Université), Paris, France [email protected] [email protected] Abstract. This contribution presents the research-creation project SOIL (Soil Observation through musical Interaction and Listening), which investigates soil as a sonic and compositional medium. Drawing on ecoacoustics, sound ecology, landscape studies, and music technology, the project proposes to develop new listening devices and compositional strategies that foreground the vibratory and spatial properties of soil. Conducted in urban gardens in Saint-Denis (France), with an opening towards other landscapes such as glaciers, the project is rooted in collaborative practices with the musicians of the Longleash trio and different audiences, in order to foster a shared and sensitive attention to urban soils. Our hypothesis is that listening to and composing with soil allows us to challenge utilitarian and extractivist views, and instead reveal its ecological, symbolic, and memorial dimensions. While building upon methodologies from ecoacoustics and passive acoustic monitoring, our project proposes a complementary approach grounded in qualitative, sensitive and spatial listening. By designing multichannel recording devices adapted to the ground, we aim to open new possibilities for musical composition that engage both the material and symbolic poetics of soil. These experiments, documented online are tested during public events such as soundwalks and concerts. They aim to foster an attentive and situated perception of the underground environment, exploring how musical composition can mediate a sensitive relation to soil. Keywords: Soundscape ·Structure-born Sound ·Geophone Array · Spatial Audio ·Sound Space ·Auditory Landscape ·Soil All rights remain with the authors under the Creative Commons Attribution 4.0 International License (CC BY 4.0). Proc. of the 17th Int. Symposium on Computer Music Multidisciplinary Research, London, United Kingdom, 2025 ⇤equal contribution Proc. of the 17th International Symposium on CMMR, London, UK, Nov. 3-7, 2025 163 P. Goutmann & D. Schuh 1Introduction Soil is a medium commonly reduced to a utilitarian function for humans: a foundation for construction and circulation or a resource for extraction. Yet, it is a complex environment, rich in biodiversity that is often overlooked [12], and serves as the "memory keeper" of our planet, an archive composed of overlapping layers of past human and non-human cultures [22]. The contemporary perception of soil, dominated by a logic of exploitation and extractivism, tends to impoverish, destroy, and silence it. Consequently, the research-creation project SOIL (Soil Observation through musical Interaction and Listening) aims to transform our relationship with soil by fostering attention to living organisms through musical listening and composition inspired by these environments. This article present the findings based on the following problematic: how these spatial recordings can be treated both as a mediation device and as true musical material in order to engage reconfiguration of poetics and representation of soil. In the first section, we discuss the ecological and aesthetic implications of our research project. In the second, we present the first prototypes and the methodology for capturing underground sounds. In the third section, we analyze the results and explore future directions for the project. 2Listening/Composingwithsoil:asensitiveapproachof sound ecology 2.1 An essential ecosystem for life, an unthought to be revealed Soil is often perceived as a surface, a space for circulation, a foundation for construction [12], or a resource leading to extractivist practices [1]. This perception has resulted in a form of deterritorialization and destruction: soils are stripped, sealed, and transformed into "non-soils". However, soil is a vital ecosystem essential for the development of life, providing irreplaceable ecosystemic services [29]. Building on the idea that "our relationship with soil generates different ways of thinking about and experiencing it" [22], we advocate for a sensitive and qualitative approach to soil, one that emerges through a musical relationship of listening and composition. Through the SOIL project, we sought to reconfigure how soil is perceived, revealing its richness and depth via diverse mediation formats. These soundscapes, created using recording devices adapted to the studied environment are designed to be shared with diverse audiences (non-academic public, children and musicians). 2.2 State of the art In music, exploring the soil means approaching vibration through solid structures: a structure-borne approach of sound [18]. In the field of musical listening, structure-borne listening approaches are rare [4]. Notable contributions include Proc. of the 17th International Symposium on CMMR, London, UK, Nov. 3-7, 2025 164 Solidian Soundscapes Cassandra Felgueiras’s structure-borne instruments and Pascale Criton’s "solidian listening", which advance inclusive sonotactile approaches by conveying sound through solid materials [5]. In the field of sound ecology and practices such as field recording [9], or environmental sound capture, structure-borne experiments remain scarce. Existing works often focus on a naturalistic rendering of recorded environments [24,30]. The field of bioacoustics is beginning to develop asetoftoolsandmethodologicalapproachesformonitoringsoils[31,15,19,26, 20]. These methods are tailored to their discipline, primarily focusing on passive monitoring of biodiversity through quantitative acoustic indices. However, based on our initial research, there are currently no recording devices designed to capture the spatial qualities of sound (movements, localization, envelopment, directional activities) within the soil suited for musical and compositional projects. Therefore, one of the project’s goals is to propose geophone array prototype for structure-borne sound fields, adopting a musical approach that is attentive to the spatial dimensions of sound. 2.3 Choosing our fields The SOIL project relies on two research sites that serve as our recording environments. These two locations were chosen for their role in resisting soil artificialization in urban areas. The Garden in motion at the Maison des Sciences Humaines et sociale Paris Nord (MSHPN), established in 2015 on a former industrial wasteland, was designed as a water reservoir and as an ecosystem where living organisms self-organize within a post-industrial city. Meanwhile, the Liz Christy Garden in New York was created in 1973 by Liz Christy and the Green Guerillas group. This garden emerged from ecological struggles against urban densification and in favor of biodiversity development in the city. Despite their different management approaches, both gardens function as ecosystems of resistance against the challenges of urban soil densification and artificialization. We hypothesize that their soils hold an interesting sonic diversity [27], which we aim to explore and reveal through underground sound recordings, as well as through the restitution and recomposition of these recorded soundscapes. These sites thus provide a valuable framework for investigating themes of sound ecology, particularly in the context of developing listening-based attention devices for soils. In this article, we explore our experiments in the first field, the MSHPN garden were we built our methodology. 3 Exploration Pipeline & Methodology This section presents the recording specifications, followed by the morphological identification process, the design of the audio engine, and finally, the sound diffusion. The entire workflow was first tested in a monophonic recording setup to refine the method before expanding to a multipoint recording setup. All the monitoring and processes are performed using High-Order Ambisonic (HOA). Proc. of the 17th International Symposium on CMMR, London, UK, Nov. 3-7, 2025 165 P. Goutmann & D. Schuh For now, each geophone signal is projected onto virtual sources to enable periphonic listening along with the advantage of an intermediate representation that enables system-independent processing and facilitates binaural auralization4. 3.1 Recording Technics Although numerous devices have been developed for the detection of directional energy, their use often remains limited for creators due to financial, technical, and logistical constraints. The present project does not aim to isolate a specific type of source (seismic, anthropogenic, or non-anthropogenic). Instead, it seeks to capture traces within the audible domain, regardless of their origin, while privileging a practical, music-oriented approach as a preliminary step toward the development of a more refined geophone array. For this purpose, we employ sensors readily available on commercial platforms, requiring no prior expertise in electronics from musicians. For an overview of sensors for sound in soil, see [19]. To achieve this, we used geophones [8], from LOM Audio (10-1000Hz, 80.V/m/s) which are electrodynamic transducers with a moving coil and a resonance frequency of 14 Hz. This type of transducer has an omnidirectional pickup pattern and is sensitive to electromagnetic waves. In our project carrying musical and aesthetic approach, electromagnetic interference in some recordings is considered an integral component of the signal rather than an artifact to be systematically removed. For the first outdoor recordings, two configurations have been tested: (1) Placing it at the surface (2) Burying the geophone at a depth of approximately 30 cm to isolate geophones from the aerial sound. In the end we chose the first option, in the attempt of avoiding noises caused by the soil’s displacement. The recordings were carried out at different times of the day and at various locations within the garden of MSHPN notably beside a compost5.Additionally, for each recording, a Neumann KM183 was placed above the geophone as a reference point for the surrounding sound activity at our recording location. Once the chain was tested for the monophonic setup, a set of four geophones were placed in a tetrahedral configuration for the underground setup, and a First Order Ambisonic (FOA) microphone (Sennheiser Ambeo) was positioned on the surface. A primary array was tested: an equilateral triangle inscribed in a circle with a 15 cm radius, featuring three geophones at the top and one approximately 15 cm below the center of the circle (see Fig. 1). 4All tests were conducted at the Centre de recherche en Informatique et Création Musicale (CICM) sound testing studio described in section 3.3 and binaural auralization using Lecomte’s binaural decoder [16] based on Head Related Impulse Response (HRIR) Neumann KU 100 [2] 5We specifically chose the proximity of a compost, as it appeared to present higher levels of biophony. Recordings were conducted between January and May 2025, from 9 AM to 7 PM, for a total duration of approximately 20 hours. Proc. of the 17th International Symposium on CMMR, London, UK, Nov. 3-7, 2025 166 Solidian Soundscapes Fig. 1. Recording session in the MSHPN’ garden with tetrahedral array of geophones and FOA microphone 3.2 Finding the substrate In these recordings, different kinds of sound substrates are present: predominantly anthropophony (such as subway, car traffic, electromagnetic interference, airplanes), along with probable instances of biophony and geophony (e.g., water movement in the ground) [23]. First, the recordings were listened to in their raw form and then processed using low-pass filtering at 1 kHz and normalization. In the initial short recordings (<5 min.), we used a spectrogram to locate sound events. Once the recording method was stabilized, we conducted longer recordings lasting several hours. At this stage, we calculated the Acoustic Complexity Index (ACI) [21], as implemented by the Soundecology project6,on30-second fragments to identify the most significant variations in the recordings. Even though it is difficult to argue that the sample data are representative of the environment, this relative richness of morphologies remains relevant for musical approaches. 3.3 Low-Frequency Spatialization Because the sound material from the takes is mostly below 1000Hz with a concentration under 100Hz, it seems important to explore emphasis of lowfrequency content spatialization. In practice, subwoofers are frequently neglected in loudspeaker setup for spatialization. Most Ambisonics decoding tools are 6https://ljvillanueva.github.io/soundecology/ Proc. of the 17th International Symposium on CMMR, London, UK, Nov. 3-7, 2025 167 P. Goutmann & D. Schuh loudspeaker-agnostic, and they don’t take into account the type of speakers used. Zotter recommends to apply a high-pass filter around 70-100Hz to the Ambisonics stream and in parallel send the first Ambisonics channel with a low-pass filter to the subwoofer section [32]. The monitoring setup used for the project is composed of 16 Genelec 8030A (58-20kHz) arranged on a hemisphere and 4 Amadeus ML18 subwoofers (35-350Hz) as shown in the Fig. 2. It offers the possibility to experiment with the subwoofer integration, so we tried two approaches to handle the low frequencies: adaptation of HOA 3D stream and a HOA 2D encoding parallel stream. Fig. 2. Loudspeaker setup representation in MATLAB The first approach involved taking the HOA 3D stream and retaining only the harmonics where |m|=l(Y0,Y 1,1and Y1,1)andsendingthemtoafirstorder 2D decoder for subwoofers. The second approach was to perform a parallel 2D encoding/processing at first order, where only the azimuth of each source was provided to the encoder. The first approach has the advantage of saving an encoding block but results in a loss of low frequencies when sources are projected with a non-zero elevation. Therefore, the second approach was preferred. Initial tests conducted in the studio showed that when we project a source onto the horizontal plane and adjust its azimuth using the speakers and subwoofers, the localization of low frequencies provided by the subwoofers is clearly identifiable. 3.4 Spatial Audio Processing The spatiality of sound is often reduced to spatialization and acoustic modeling of spaces. The practice of spatialization invokes models of spatial representation dominated by Euclidean representations that reduce sources to points [10]. In this context, we can identify two main approaches to spatial processing: (1) Proc. of the 17th International Symposium on CMMR, London, UK, Nov. 3-7, 2025 168 Solidian Soundscapes "Source-oriented", which inherits from the Euclidean conception of space (2) "Field-oriented", which applies global processing to the soundfield. The source-oriented process takes a mono signal as input and projects the processed result into space [17,14,25]. This approach is the most commonly used. The other well-known strategy, based on the work of [28,11], involves applying digital audio processing directly to the signals from the ambisonic stream. To generate diversity, we tested both approaches. Based on the different sound morphologies identified during the substrate extraction phases, we defined a sound dictionary, to which we applied both approaches (source-oriented granulation and field-oriented granulation). The resulting sounds were rich and musically exploitable. In the piece presented in Section 4.1 D.Schuh deployed both approaches including an original monophonic granulator, an ambisonic feedback matrix and the tools developed within the framework of abc.lib [3]. 4 Experimenting with the devices 4.1 Mediations: exploring soil soundscapes with different audiences Returning to the project’s hypotheses - namely, whether it is possible to make the soil audible as a space endowed with depth and spatiality, and whether it is possible to awaken different publics to these dimensions by means of listening - we tested two types of mediation devices. The first concerns mediation devices intended for non-academic publics, and for children in particular, in the context of research outreach and popularization of science. This section describes these devices and their impact on the audiences encountered. The second type of device -aconcert-installation-isdescribedinthenextsection. The SOIL project was presented on 17 April 2025 during the "Mini festival scientifique sonore" organized by Les Férus de sciences (a science-culture institution run by Métropole du Grand Nancy). This festival drew several hundred people, mainly families accompanied by children (between 6 and 18 years old), who were able to experience listening to the soil recordings on headphones, in a binaural rendering. Headphone listening to the binaural rendering7had several effects on the different groups who were able to experience it. The publics were able to perceive the impact of anthropophony: there is constant vibration due to road traffic, nearby construction sites, and underground networks. The reproduction of the sound space, allowing for effects of source localization and trajectory, reinforced the sensitive immersion in what one could call the soil soundscapes. Listening to these spatial audio8made a strong impression on some children, ranging from surprise to wonder. Listening to the soil - and, a fortiori,listeningtosoilasasoundspace-enabledustovalidateour initial intention: to convey the idea that soil is not a surface but a sonic milieu, a sound ecosystem endowed with spatiality, in the same way as aerial sound ecosystems. 7without processing apart from a low-pass filter around 1500 Hz 8Audio example: https://soil.hypotheses.org/ecouter-carnet-de-recherche Proc. of the 17th International Symposium on CMMR, London, UK, Nov. 3-7, 2025 169 P. Goutmann & D. Schuh Fig. 3. children listening with headphones The second mediation device that we tested was trialed on 6 June 2025, in the garden in motion of the MSHPN, during the Ministry of Culture event Rendez-vous aux jardin.Duringthiseventtwogroupsofaroundtenadultswere first able to visit the garden in a guided tour by Marianne Hérard9in order to understand its ecosystem before stopping at listening stations. Four stations were set up, each consisting of a geophone sensor connected to a Zoom recorder, itself connected to closed-back headphones. Here the public were able to experiment with real-time listening to the garden’s soil. Those who experienced it perceived the mainly human activity characteristic of a post-industrial city such as Saint-Denis. The groups were then invited to a mini-lecture in the garden during which they were able to listen to our recordings diffused in FOA-2D over aquadraphonicsystem.Onceagain,thediscussionssurroundingtheselistening sessions provided audiences with an opportunity to articulate their responses to these sensitive forms of mediation. Such a device proves effective for disseminating research and raising awareness of soil sonic ecology among non-specialist audiences. For this axis of the project (awareness-raising) it would seem pertinent in future projects to associate ourselves with ecoacousticians specializing in soil biodiversity. Indeed, our project is grounded in an approach to musical and sensitive listening. We describe in the following section another type of device that called for musical composition. 4.2 Earth as earth: a way to explore the substrate musically Another central question of the project was whether the spatial qualities and timbres of sounds recorded in soil can function as a musical substrate for com9Head of outreach and scientific programs at the MSHPN Proc. of the 17th International Symposium on CMMR, London, UK, Nov. 3-7, 2025 170 Solidian Soundscapes position, and, if so, whether the public restitution of such a piece can also operate as a sensitive form of mediation. Commissioned by the Longleash trio10,D.Schuh addressed this question in the mixed piece Earth as earth. The soil recordings served as the piece’s point of departure. Initial textures were used either as given or lightly sculpted with equalization. A custom-built granulator was then employed to develop the granular dimensions latent in these initial soil textures. Building on the fixed sound structure and timbre, the realtime electronics were organized around spatial sound synthesis inspired by the "spaces of the soil", whose opacity to human traversal gives them an abstract, imaginal character. In this way of thinking the sound milieu, circulation and transformation of sound are controlled through a feedback matrix in Max (see Fig. 4) that composes spatiality in the ambisonic latent space, allowing for indeterminacy and hybrid timbral and spatial quality in sound11 Fig. 4. earth as earth Max patch Earth as earth is a mixed music piece which comprises three large sections built from three fixed soundtracks, with an improvised interlude between Parts II and III. The interlude is guided by notated cues specifying playing modes (see Fig. 5); the performers improvise from these cues, punctuated by sonic objects derived from the soil recordings. The poetics of the work and the prop10 https://www.longleash.org 11 Audio example: https://soil.hypotheses.org/earth-as-earth-diane-schuh Proc. of the 17th International Symposium on CMMR, London, UK, Nov. 3-7, 2025 171