SOUND: Nikki Lindt’s Underground Sounds

Have you ever wondered what the inside of a tree sounds like? The mud beneath a streambed? The soil in a field of wildflowers, or the dirt under a bed of fallen leaves when acorns drop onto them? In Prospect Park, there is now a way to tune in to this underground world.

During a five-minute walk in New York City, you can find QR codes that lead you to charter schools, cannabis clubs, notices about pesticide spraying, and bus schedules. But in the park’s Ravine, mounted on eight fenceposts, these silent chiaroscuros offer a portal to a hidden dimension: artist Nikki Lindt’s Underground Sound Project, a virtual soundwalk featuring noises Nikki recorded in the mud, soil, tree trunks, lakes, and streams of Brooklyn’s Prospect Park and across the five boroughs—from Jamaica Bay Wildlife Refuge in Queens, to Oakwood Beach in Staten Island, to Thain Forest in the Bronx, to Manhattan’s Central Park (where she picked up the rumble of the subway passing under an oak tree). Hover your phone over one of the codes, and you will be inducted into a secret world beneath the city, one that’s both ordinary and astonishing.

To capture the sounds, Lindt uses a simple homemade “contact microphone”: a hardware store screw picks up the vibrations of anything it touches and transmits it to a Piezo element, a piece of ceramic coated with electrodes mounted to the top of the screw. When plugged into a professional sound recorder, the contraption translates the vibrations into sounds.

Recently, I had the privilege of doing the soundwalk with Nikki, who brought along her equipment. Standing by a tree at the edge of the Dog Beach, we placed the contact microphone on the root and plugged it in. I slipped the headphones over my ears and the tree’s inner world came into focus. When a breeze passed, I heard the rustling leavees and creaking branches traveling down the length of the trunk to the root—but the sounds had an intimacy and resonance different from listening to wind in a tree from the outside. After a few minutes, I picked up on a subtle humming undercurrent that Nikki says is a base note of most underground sounds. At the same time as I was eavesdropping on the tree, I could hear my own voice—and my fingers tapping the bark—superimposed on the tree’s sounds, through the earphones as well as coming to my ears from the outside. I was both separate from and participating in the noises, observing them even as I was affecting them with my participation. “The same tree will make different sounds on different days, at different times, in different seasons,” Nikki says—and noted that you can hear sap running through maples in early spring. “It’s a changing, alive installation.”

The goal of the project, she says, is for participants to experience “total excitement and wonder at the natural world.” Because the recordings are on her website, they can be listened to anywhere, anytime—on your couch, or in any area with trees, streams, wildflowers. “If they enter a park and feel a connection, it’s a way to bring people into conversation with nature and start to feel empathy.”

Nikki, who is also a painter, first discovered the power of underground sounds accidentally, while visiting a sinkhole in Alaska for a visual art project. “The sound of thawing permafrost [in the sinkhole] was so impactful, I thought, I need to work with this.” Much of her artwork before then had been focused on loss, but when she discovered the permafrost sounds, she felt she was coming closer to the ecosystem; it no longer seemed to be rushing away through her fingers. As she began to explore the world of sound, her collaborations with scientists helped her in the process of moving on, and the idea of collaboration, alongside connection, became a cornerstone of the project.

On the soundwalk, each of the eight stops is accompanied by a video diptych of the site and its film negative, to give a visual sense of “above” and “below.” Nikki decided to add photos to the project because she felt “the sounds were so alien that people wouldn’t read the language without a hint.” Here, for example, is a diptych of the third stop, the forest floor. On her recording, you can hear a hush, a rumbling, and a warbly thumping, with a steady whispery undercurrent not unlike the air in a plane cabin. Then, after a few moments, there’s the shockingly loud hollow thunk of acorns plopping onto the ground, over the crackling of dry leaves. At the same time as I was listening to the acorns, two girls in spandex passed by, and one said to the other, “They have a lot of cardio and they do these, like, stations…” This kind of moment happens all the time on the soundwalk: the juxtaposition of ordinary moments and oblivion to the world right under our own feet. Nikki sometimes marvels that a fistful of soil contains hundreds of thousands of organisms: 100 million bacteria, 100,000 protozoa, 10,000 nematodes, and up to 5,000 insects and worms. “What do they experience?” she asks. This project “opened up other ways to relate” for her, different from her connections through visual art.

She began making her recordings for the New York City project in fall 2020, but the project began in earnest with the big snowfall in winter 2021; most sounds were recorded in the four seasons of 2021. One of the most surprising sounds she encountered was that of snow melting, a patterned sound that she surmised might be from snowflakes separating from the larger mass.

Another stop on the walk is the mud at the bottom of a lake. On the recording, you can hear the splash of ducks diving, the croaking of a branch moving in the water, and a squeaking, creaky sound like Styrofoam. I had the urge to pin down and identify the sounds, and had to will myself to let them speak their own language. Two people walked by, and their words in my language filtered through my earbuds, superimposing themselves on the burblings of the mud: “And they had the same kind of ice cream when we went to Montreal!”

To Nikki, there’s an essential difference between communion—becoming one with something else—and connection. While she is wary of assigning agency to the world she records, she says, “I am open to the fact that I am sensed,” but “I don’t dare to say I knew that the tree knew I was there.” It’s “a completely different way of sensing. You feel you are a part of something bigger” than what you are hearing. Primarily, Nikki just wants people to know about this hidden world, “to release this place I’ve been in touch with, as a way for people to feel a connection and empathy.” The experience of the soundwalk could lead to a feeling of stewardship—or not. On a simpler level, it’s just a way to bring people into urban parks. Some people have never visited parks that are practically in their own backyards, she says.

We stopped on a bridge over a stream and Nikki dropped her microphone—this time a hydrophone rather than a contact microphone—over the edge into the water. Through her headphones, I heard a plinky metallic sound, like a guitar being plucked, and then the deep, dark undercurrent that is the “hallmark” of these recordings. When she moved the microphone into a small waterfall, I heard a hollow rumbling gurgling, like a faucet running, over a layer of a knocking that perhaps came from water hitting the rocks. When I handed the headphones to Nikki and asked how she heard it, she paused, listening closely. “There’s more chaos in these areas with a lot of water coming down. Maybe you can hear the bubbles that are created.”

When she started the project, she asked an acoustical ecologist what she should use to record underground. Astonishingly, he didn’t know what to recommend and and told her he didn’t know of anyone doing this kind of work. He offered her the advice to use a hydrophone, which is used to record underwater sounds (like dolphin communication), and suggested she could also try it in the earth. She eventually figured out how to make the contact microphone for “dry” recordings, but continues to use the hydrophone for anything wet. Nikki has gradually realized she is a pioneer: even today, she is the only person she is aware of who is recording broader underground acoustic systems in this way (and not as a scientist with a research subject) on a large scale, and offering the results to the public.

Another recording is the noise of rain on soil. To me it sounds like an oily blurbling, with the musicality of popcorn popping, with a hollow rippling like someone blowing over the top of a soda bottle. At first, she says, she saw the human element as separated out: Darn, I have to start over, she would think when a human sound interrupted her recording—but now she sees that “the city is part of the ecosystem. You start to realize it’s all one.” The world beneath our feet is a silent sentinel, listening in on and registering our footsteps, our conversations, our solitary tears, the tires of our strollers and bikes. As I was leaving the park, I passed a group waiting for a toddler to catch up to them. “She doesn’t quite walk like a New Yorker—just yet,” said her dad with a chuckle. The little girl was standing stock-still in the middle of the path, listening.

The Underground Sound Project will be available in Prospect Park’s Ravine through May 2024; the recordings are available anytime on the website.