During my inaugural spring soundwalk through the Arnold Arboretum in early April 2023, I spent a significant amount of time with an eastern white pine. The tree stands with no immediate neighbors, in close vicinity to a rippling brook below, next to the foot of a little hill where other trees, with the help of a human hand, form a more dense ecosystem.
I walk slowly towards the trunk, stepping carefully in the gaps of the tree’s partly revealed root system. Predictably, most of the roots stretch directly towards the water. After sitting by the tree and listening to the surrounding soundscape, I open my backpack and pull out two hydrophones. These are special microphones that bioacousticians, environmentalists, sound artists, and scholars across the world use to listen to and assess the quality of underwater environments. The hydrophones I use in my work can also serve as contact microphones. By attaching them to a solid surface of almost any object, contact microphones sense the vibrations that propagate through it. Unlike traditional microphones, they are almost entirely insensitive to airborne waves, instead providing the listener with access to another, often imperceptible or overlooked, yet fundamental dimension of the space around us, namely its continuous vibration.
As a sound artist and scholar interested in the multifaceted and multitemporal nature of our landscapes and soundscapes, I use such microphones for various purposes. I have deployed them in urban contexts to listen to vibrating elements of urban infrastructure: bridges, radio, mobile network towers, and banisters. In parks and forests, I have been using the same devices to attune with inner soundscapes of tree trunks and nurse logs orchestrated by the vibrant life patterns of beetle larvae and other insects. I have also used such microphones to shift my listening position, letting the trees guide my perception of the forest or a city. Attaching the microphones to tree trunks or their branches temporarily turns them into extensions of my senses, allowing me, and those who join my soundwalks, to sonically connect with the surrounding ecosystems. In enabling various elements of the environment to mediate its soundscapes, one quickly becomes aware of the unbearable degree of anthropogenic noise that fills and pollutes our natural and urban habitats.
After gently positioning my hydrophones next to the eastern white pine’s roots—I carefully adjust the levels on the interface of my audio recorder. Soon, an unusual amalgam of sounds reaches my ear. I can hear the traffic din from the nearby road. I hear the wind above gently brushing the tree branches. I can hear occasional clicks and pulses of the roots pumping the water from the brook nearby. In the background, I can detect the rushing water of the brook itself. The longer I listen, the more my sense of the present moment dissolves. Significantly augmented by my sound equipment, my attention is at once grounded and distributed across multiple dimensions.
Aural attention to this constellation of sounds can teach us several things. Firstly, that sounds are always relational events: the sound we hear at any given moment never entirely belongs to one or another entity or object, but emerges from an interaction of diverse forces and materialities, through time and space. In modern societies, we have been trained to divide our senses, to dissect and isolate diverse phenomena from their spatial and temporal contexts in order to understand them better. The development of scientific instruments operating within the boundaries of individual senses—optical or acoustic, for example—has only increased our tendency to see and hear things as independent and hence easily categorizable, indexable, and controllable. In my work, I try to advocate for listening—both unaugmented and aided by microphones and other technologies—as a practice of attention to connections that underlie our experience of the surrounding space. Surely, many technologies I and other field recordists use in their work historically stem from the lineage of scientific instruments of colonial expansion and control, geared towards collecting traces of other cultures and environments. While acknowledging this fact, my approach resonates with that of anthropologist Anna Lowenhaupt Tsing, who suggests a burning need for rethinking the role of technologies in the times of Anthropocene. She asks how technologies can be decoupled from problematic motivations that steered their development, to instead help to reveal the realms that modernity has over the course of centuries ignored and damaged. Artistic practice, she argues, is one territory where this important change can be pursued. Similarly, in my conceptual, practical, and artistic approaches to listening technologies, I like to experiment with technologies as tools rather than imposing one perspective, to question our certainties and open up to a multiplicity of other worldviews and listening positionalities. Many artists share this pursuit, including a growing number who are specifically interested in the sounds of trees—for example, Julia Adzuki, Jez riley French and Lau Nau, Alex Metcalf, Giorgio Magnanensi, Julie Andreyev, and Liz K. Miller.
Let us get back on the Arboretum’s ground. Or rather, below. Another immediate lesson from listening to that eastern white pine is the realization of the stunning scale of a tree itself: its immense, invisible presence under the ground, an element in a vast network of life whose entirety will always evade any kind of perceptual and technological capture. Through that kind of relational hearing, my always only partial comprehension of trees has transformed and keeps transforming. Once identifying them as vertical elements of our shared environments—an impression imposed by our sense of vision—today, I cannot but approach them as vastly horizontal beings.
Another immediate lesson from listening to that eastern white pine is the realization of the stunning scale of a tree itself.
This, in turn, informs my visual perception. Senses are interconnected. They feed each other. Hearing—and by this term I don’t mean reception of acoustic signals only, but also vibratory ones–can help us see and imagine the world around as from a different perspective, as “temporary aggregations of relationships,” as biologist David George Haskell puts it in his 2017 book, The Songs of Trees.
In the scientific domain, investigations by ecologist Monica Gagliano and others suggest that the roots of trees and other plants have the ability to detect water sources by sensing vibrations produced by water movements in subterranean structures like pipes, even in the absence of moisture. Obviously, that sensing capacity is far from how we commonly understand “listening”—namely, as the reception of airborne waves. Nevertheless, this intricate technique of sensing vibrations of the surrounding world and responding accordingly might aid us in expanding not only our understanding of the trees as living, sensitive entities, but also the very notion of listening, as I have written elsewhere. Similarly, we have recently been learning that plants emit ultrasonic sounds, such as short rapid bursts when exposed to harsh conditions, as recently documented by plant scientist Khait Itzhak and colleagues in the journal, Cell. Researchers are still not sure about those signals, whether they are merely byproducts from a disruption in the transfer of liquids in their tissue or there is something more to them.
While Western scholarship has only recently begun to grant hearing to trees and other forms of vegetation, some indigenous epistemologies have developed and cultivated such knowledge for millennia. For example, Robin Wall Kimmerer, environmental and forest biologist and member of Potawatomi Nation, writing in The Mind of Plants: Narratives of Vegetal Intelligence (2021), reminds us that “(t)he Indigenous story tradition speaks of a past in which all beings spoke the same language and life lessons flowed among species. But we have forgotten—or been made to forget—how to listen so that all we hear is sound, emptied of its meaning.”
My visit to the Arboretum was one in a series of field recording sessions and soundwalks from 2022 to 2024. The 2023 soundwalk series was titled “Arboreal Sonorities,” while the 2024 series was named “Nature Amplified: The Secret Sounds of Trees.” While two of the soundwalks in 2023 were open to the general audience, one was specifically tailored for visually impaired and blind individuals. Soundwalking is a practice that involves traversing a space with a primary focus on listening. This practice emerged as a method for investigating the state of local and global soundscapes through the research of the World Soundscape Project (WSP). Established in the 1960s by Canadian composer R. Murray Schafer, the WSP comprised scholars, environmentalists, and artists dedicated to redirecting people’s attention from landscapes to soundscapes as they became subject to the increasing intensity of noise from the industrial transformations of our lived environments. In her foundational essay “Soundwalking” (1974), group member Hildegard Westerkamp defined a soundwalk as “any excursion whose main purpose is listening to the environment. It is an exploration of our ear/environment relationship, unmediated by microphones, headphones, and recording equipment. It is an exploration of what the ‘naked ear’ hears and how we relate and react to it.”
Forest soundscapes vary depending on factors like the types of trees, the species they host, and the micro-climate they foster.
In my approach to soundwalking, however, I work with an array of sound technologies mentioned earlier. I use them cautiously, not to represent the world or to gain an accurate picture of otherwise imperceptible realms, but rather to open up listeners’ imaginations to these hidden realms and temporalities. My aim is to hint at their existence and raise awareness, which, hopefully, may lead to tangible expressions of respect, appreciation, and care for them. During our soundwalks in the Arboretum, participants were provided with specialized receivers and headphones through which I transmitted previously recorded sounds. In addition to the sounds of trees from the Arboretum, I integrated soundscapes from other locations I had explored in recent years during my postdoctoral research, such as the Pacific rain forests and the hammocks at Canaveral National Seashore.
We began our walk at the Hunnewell Visitor Center, making our way towards the marsh near the dawn redwoods. As we walked, we listened to an evolving soundscape that started with the immediate sounds of the marsh, accompanied by a previously recorded dawn chorus dominated by the recently returned red-winged blackbirds. As we moved further from the marsh, I began to incorporate recordings of dawn choruses from different geographical locations. These included a forest in Lidingö, Sweden, featuring a blend of larches, oaks, pines, and birches, providing a lush nesting ground for tits, finches, blackbirds, robins, nuthatches, and woodpeckers. We also ventured into a rainforest in Vancouver, home to hermit thrushes, robins, wrens, warblers, and barred owls, among other species. Forest soundscapes vary depending on factors like the types of trees, the species they host, and the micro-climate they foster. Thus, in addition to learning about the bird species characteristic of a given forest environment, careful listening to birds can offer insights into other intricate aspects of the for- est, including its age and condition, often marked by the activities of woodpeckers.
Exiting the marsh, we navigated the denser part of the Arboretum. Here, I began mixing in sounds of rain and storms captured in the Arboretum and other locations. Depending on the type of forest, raindrops sonically activate their multiple components in diverse ways, with varying intensities and rhythms. Therefore, to a trained ear, familiar with the differences between the types of vegetation in specific forests, the sound of rain reveals a multitude of species and the relationships between them that constitute the forest’s ecosystem. Exposed to sudden storms and heavy rainfalls, with directions radically altered by unexpected wind gusts and hurricanes, the dry palm leaves and their fallen boots in Canaveral Seashore’s hammocks create a highly particular sonic signature, unique to that part of the world. Similarly, ancient rainforests in the Pacific Northwest, with their abundance of hollow tree trunks and nursing logs adding to the already thick foliage, resonate in a way that is highly distinguish- able from the sound of rain in, for example, a pine-dominated forest in central Sweden. As we walked, we listened to these different instances of rain and storms in forests from various perspectives, some enabled by my work attaching contact microphones to tree trunks and branches to gain a better insight into the variety of sonic effects—percussive shots, extended squeaks, resonances—from within, inside-out.
The sound of rain reveals a multitude of species and the relationships between them that constitute the forest’s ecosystem.
After emerging from this augmented experience of rain in the forest, I shared with the participants a range of subtle and intimate sounds generated within different parts and layers of the trees’ bodies, including the hybrid yew, eastern white pines, and white and Siberian elms. I was particularly keen to share a recording of the root system of a Siberian elm I made in July 2024. Siberian elms are known for their massive roots that span wide patches of land, occasionally popping to the surface here and there. On one of my field study walks, I encountered one with an exposed root that hosted several cavities filled with small pools of rainwater. After gently submerging my hydrophones and attaching geophones, I was soon invited into an intricate soundscape. It was dominated by a continuous series of pops and clicks as the water was soaking into the root’s tissue. This surprisingly loud, staccato-like pattern was accompanied by much more irregular, high-pitched noises and rustles made by insect larvae submerged in the muddy layers of these tiny pools. Besides those sounds, the root system transmitted vibrations from the upper part of the tree, including those caused by the wind brushing the tree crown and even cicadas persistently calling their mates. Predictably, this unique soundscape was persistently disturbed by car and air-traffic noises amplified by the large volume of the tree and its enormous root system.
As we walked further, I invited participants to touch the bark of the trees and experiment with the various sonic effects resulting from these interactions. By affixing contact microphones to the surface of a cork tree, we delved into the rich sounds produced by our contact with its exceptionally thick yet resonant bark.
We continued by tuning into the inner soundscapes of fallen tree logs and stumps, orchestrated by, for instance, by beetle larvae residing within and wasps attempting to establish their nests in numerous holes, many of which appeared to be the work of woodpeckers. As we progressed, we passed by a small marsh where the roots of highbush blueberries were submerged, surrounded by an array of aquatic plants. Using hydrophones, we captured and listened to the subtle pops of photosynthesis. Our journey concluded at one of the three ponds at the junction of Meadow, Bussey Hill, and Forest Hills Roads. While listening in real time to an array of underwater chirps and squeaks generated by numerous aquatic insects, possibly dragonfly larvae, along with sounds and vocalizations of bullfrogs and small fish, I gradually mixed in hydrophone recordings from my visit to Mosquito Lagoon in Florida. This environment is known for its rich variety of species, supported by an intricate network of mangroves—a unique type of coastal vegetation made up of salt-tolerant trees and shrubs partly submerged in water. The sounds we listened to came from a continuous field recording I made there in March 2023, which included shrimp, oyster toadfish, bluck drum, cricket frogs, bottlenose dolphins, and manatees.
As mentioned earlier, the way sound propagates and how we experience it encompass more than just an acoustic, airborne phenomenon. It always concerns vibration. Such vibrational qualities hold particular significance for visually impaired individuals, whose sensitivity to both sonic and tactile stimuli is often highly refined. The version of the soundwalk tailored for visually impaired participants emphasized these aspects. While visually impaired people use listening daily to extract cues from the environment for safe navigation, the soundwalk presented an opportunity to explore listening from a different perspective and with a different intention. The potential risk was that by redirecting attention to these other, typically imperceptible auditory registers, their sense of navigation might become disoriented. Navigating between the amalgam of immediate and distant, prerecorded soundscapes was indeed challenging but, as participants reflected, highly rewarding.
It’s important to emphasize that the soundwalks designed for the Arboretum were not meant to be ends in themselves. Instead, I saw them as invitations to engage in listening to the surrounding world on a daily basis— encouragement to ponder not only what we focus on when we listen to the world around us, but also how we listen.
I kept reflecting on how much of what we hear there daily doesn’t speak for what we encounter, namely the rich collection of trees.
As I soundwalked the paths of the Arboretum, using either my microphones or my “unarmed” senses, I kept reflecting on how much of what we hear there daily doesn’t speak for what we encounter, namely the rich collection of trees. The soundscape of the Arboretum is excessively dominated by anthropogenic sounds, particularly the noise of car traffic that envelops the entire area. The proximity of the hospital adds to the soundscape’s contamination with loud sirens, and many routes of dense air traffic cross the sky directly above the site. Almost every recording I made in the Arboretum during my fieldwork, including the gentlest rustles of water making its way through the root systems, has a disturbing imprint of traffic noise. Some of this noise comes from vehicles used within the Arboretum itself.
Given this omnipresence of anthropogenic noises surrounding the arboretum, changing the overall sonic experience might not be possible. It is after all a garden, and human activity is as much a part of its soundscape as the chatter of underwater insects. Against this pervasive and inescapable realm of human-generated noise that inevitably pervades the site, soundwalks can offer a reminder that beyond the thick layer of our noisy urban fabric lies a rich realm of nature’s activities, whose sonic imprints are much less invasive and obtrusive, if perceptible at all. If we pay attention, there is much to learn from these hidden realms.
Jacek Smolicki is a Stockholm-based cross-disciplinary artist, designer, researcher and educator. His work explores temporal, existential, and technological dimensions of listening, recording, and archiving practices in human and more-than-human realms.
From “free” to “friend”…
Established in 1911 as the Bulletin of Popular Information, Arnoldia has long been a definitive forum for conversations about temperate woody plants and their landscapes. In 2022, we rolled out a new vision for the magazine as a vigorous forum for tales of plant exploration, behind-the-scenes glimpses of botanical research, and deep dives into the history of gardens, landscapes, and science. The new Arnoldia includes poetry, visual art, and literary essays, following the human imagination wherever it entangles with trees.
It takes resources to gather and nurture these new voices, and we depend on the support of our member-subscribers to make it possible. But membership means more: by becoming a member of the Arnold Arboretum, you help to keep our collection vibrant and our research and educational mission active. Through the pages of Arnoldia, you can take part in the life of this free-to-all landscape whether you live next door or an ocean away.