Hubbard Fellowship Blog – Kate Explores Soundscape Ecology

This post is written by Kate Nootenboom, whose Hubbard Fellowship is fast coming to a close. Her fellow Fellow, Sara Lueder, finished up this week and Kate will be leaving after next week. Shortly after that, our two new Fellows will be arriving (look forward to introductions soon!). Each Fellow works on an independent project while they’re here. Kate’s project included an exploration of soundscape ecology and the acoustics of prairies. I think you’ll agree it’s a fascinating topic! – Chris

How often do you go to a prairie, and close your eyes?

My guess is that most of us default to visuals when taking in a landscape. It makes sense – depending on the season, prairies can be vivid scenes of colorful blooms, shifting shades of earthen hues, or vast canvasses of winter white. This very blog is a testament to the joys of the optical, but today I’m here to humbly request we give one of the other senses a little time in the sun.

Over the course of this year, I’ve been tuning in, quite literally, to the prairie soundscape, as part of my independent project for the Hubbard Fellowship. A series of podcasts and TED Talks (link) piqued my interest in the field of soundscape ecology, and I’ve been exploring the potential of acoustic data as a tool for scientific inquiry, land management, and, of course, storytelling. I’ve summarized my findings here in the hopes that it will open your ears to an alternate and exciting way of communing with nature.

An audio recorder listens patiently to a prairie in summer. Photo by Kate Nootenboom

What is soundscape ecology?

Broadly speaking, soundscape ecology is the idea that the symphony of an ecosystem can reveal clues to its biodiversity and wellbeing. Often, sounds are partitioned into three discrete categories: biophony (sounds of the biotic world: birdsong, elk bugle), geophony (sounds of the abiotic world: rainfall, wind), and anthropophony (sounds of the man-made world: train whistles, sirens). The data can be analyzed to constrain certain indices like acoustic complexity, diversity, and evenness of an ecosystem, and to help identify the presence or absence of certain species.

An American goldfinch orates against a backdrop of anthropophony.

In addition to their scientific potential, soundscapes are also just a beautiful, but often underrecognized, way to connect with nature. For those of us who hear, sound is an important tool for absorbing our surroundings, and we use it near constantly (whether consciously or not). If well-enough-acquainted, the sounds of a prairie can reveal clues to determine the season, the time of day, even the weather. The arrival of bobolinks’ self-declaratory song heralds the coming of summer in Nebraska, and the whispery rustle of dry cottonwood leaves can tell you it is autumn, and you are near water.

That likely isn’t revelatory information for the prairie enthusiasts here, but this might be: one of the truest and most unexpected joys in this process was unearthing the unfamiliar shapes of very familiar sounds. This discovery came from scrolling through spectrograms of audio files, which plot frequency (pitch or tone) against time, with variations in color representing amplitude (loudness). Spectrograms are, of course, human inventions, and I am once again delighted by the ingenuity of our species to capture and convey natural phenomena in ways both scientific and beautiful. If nothing else, I find it oddly mesmerizing simply to see sound. 

Spectrograms of calls made by, from left to right, American goldfinch, western meadowlark, northern bobwhite, and coyote pack.

Who knew the call of a demure American goldfinch could resemble the mighty scrape of grizzly bear claws in tree bark? Or that you can see the loping motion of a triumphant coyote pack in their sound signature? The spectrogram of a bobwhite quail even mimics music notation itself: a half rest followed by an eighth note.

Northern bobwhite call.

Soundscape ecology as science

Individual audio moments, like those captured in the spectrograms above, are the poignant vignettes of a much larger story that can be told through sound. Accumulation of acoustic data over days, weeks, years, or decades will yield datasets that can be plumbed for a variety of information. Archiving the soundscape of a prairie as it exists now is a bit like entombing its residents in shale for future geologists to unearth; a “soundscape fossil record” can provide future ecologists with comprehensive information about who was here, and when. 

A pack of coyotes howl and yip into the cricket-filled night.

My foray into the scientific side of soundscapes focused on two adjacent patches of prairie near the Platte River, one a remnant and the other a restoration. I chose these units because they’ve been the subject of a multi-year study on small mammal presence, and I was interested in adding a layer of acoustic data to an existing comparative dataset. Curious to see if the soundscape changed dramatically between a remnant and a restoration, I set up devices in each unit and recorded the first five minutes of every hour for two-week intervals between August and November.

Small mammal researchers collect data in one of the prairie units where acoustic data was also collected. Photo by Chris Helzer

Once collected, I calculated six different indices from the data. A software program analyzed each five-minute clip and scored it on each of my selected indices. Acoustic Diversity Index, for example, describes how acoustically diverse the soundscape is on a seemingly arbitrary scale of 0.0 – 3.0. Below, I arranged the data into violin plots comparing audio from the remnant and the restoration for each index. I chose violin plots because a) other soundscape ecologists seem inclined to use them, and b) they are named after a musical instrument. And this project is about sound.       

Violin plots comparing acoustic indices between audio from a remnant and restored prairie. From left clockwise: Acoustic Complexity Index, Acoustic Diversity Index, Acoustic Evenness Index, Bioacoustic Index, Total Entropy, Normalized Difference Soundscape Index.

Encouragingly, the plots appear largely similar between the two, suggesting that habitat, as reflected by soundscape, does not differ drastically from remnant to restored. Deeper data analysis would reveal a more nuanced story, but hopefully this glimpse inspires curiosity for the kinds of scientific questions that can be asked and answered in this growing field.

Who else is using soundscapes?

I am far from alone in my enthusiasm for Great Plains soundscapes. Other scientists have looked at soundscapes and their effect on American burying beetle (Nicrophorous americanus) distribution, or the acoustic rebound in a prairie ecosystem following a prescribed burn (link). Still others have taken the storytelling approach by pairing soundscapes with time-lapse images to condense phenological phenomena into digestible dramas (link).

House wren?

For land managers, acoustic monitoring has huge potential for measuring biodiversity across landscapes and through time, with far less intrusion into an ecosystem than other strategies. Monitoring can take many different forms and is often best tailored to the objectives in mind, so acoustics are not a perfect replacement for existing tools. But if your objective is related to increasing insect biodiversity, or providing habitat for bobwhite quail, or attracting a prairie chicken lek to your property, progress on all these fronts can easily be monitoring by lending an ear to the land in question.

Western meadowlark

Engaging more intentionally with the sounds of the world can lead to scientific insight, effective land management, compelling stories of nature, and surprisingly visual art. Most importantly though, at least for us prairie appreciators, soundscape ecology reminds us simply to quiet our voices and thoughts so that the prairie, too, might speak.

This entry was posted in Uncategorized by Chris Helzer. Bookmark the permalink.

About Chris Helzer

Chris Helzer is the Director of Science for The Nature Conservancy in Nebraska. His main role is to evaluate and capture lessons from the Conservancy’s land management and restoration work and then share those lessons with other landowners – both private and public. In addition, Chris works to raise awareness about the importance of prairies and their conservation through his writing, photography, and presentations to various groups. Chris is also the author of "The Ecology and Management of Prairies in the Central United States", published by the University of Iowa Press. He lives in Aurora, Nebraska with his wife Kim and their children.

17 thoughts on “Hubbard Fellowship Blog – Kate Explores Soundscape Ecology

  1. Wow! Now you’re cookin’ Chris! I’m no scientist but a hobby audio recordist of natural sounds since the mid ’80’s. I really enjoy recording but my budget has forced some “work-arounds” and weather events have messed up what recording devices I’ve had (lost a $500 microphone back in the 90’s to heavy dew during a night in NW Ontario recording loons). My best attempt now is using an old parabola with a rigged digital camera with a left and right channel microphone…no moving parts with a digital camera’s audio (unless you forget to turn the auto focus off!), so no introduced recording noise. But most recording today is digital. This very interesting and fun!

  2. Beautiful and thought-provoking post, Kate!
    Yes, when I go outside and the insects and birds are singing my DNA knows many things are good in this world!
    All best wishes will go with you!!
    We are grateful for people like you in this world!
    Big thanks also to Ann Hubbard and Chris Helzer!
    From your co-fellow Sarah’s parents, Cindy & Gregg

  3. Hi all, I’m Mike O’Connor — I hang out with the better-known Marcie O’Connor here at Prairie Haven.

    Kate, I caught the bio-acoustics bug a few years ago and we’ve been gathering audio data here ever since. We collect 3 hours on either side of sunrise, an hour around noon, and 3 more hours on either side of sunset — in five locations, primarily wetland, savanna, prairie or woods. Oh, and also a gizmo that records bats, when it hears them. I maintain a little page that describes all that at http://www.EarsInTheDriftless.com — it’s a bit out of date, but gives a sense of the project.

    We use about .00001% of all that audio for a fifteen minute video that summarizes our year here. Just audio and pictures — no music, no words, etc. That’s at http://www.PrairieHaven.com/Seasons2021

    I’d love to join up with anybody else that’s collecting soundscapes like yours and ours.

    What software did you use to analyze the audio? I’m always on the hunt for new, easier-to-use tools in that arena.

    Great job!

    • Hi Mike,

      Thanks for reaching out! Always great to connect with other soundscapers. I’m a big fan of the Driftless Area too- I caught the prairie bug as a college student in glaciated Rice County MN, not too far west of you.

      For the analysis in this post, I mostly used Rstudio with the packages seewave and Soundecology. I’m no expert with R, but was able to google my way through it fairly easily. For viewing spectrograms of WAV files, I use Audacity, but I’ve heard good things about Adobe Audition as well. Two programs that I find interesting but don’t have much experience in are Kaleidoscope and Arbimon. The latter has a cool feature where you upload a “template” of a certain sound, for example a northern bobwhite call, and it will comb through all of your data and identify as many bobwhite calls as it can based on the template.

      I love what you and Marcie are doing with your sound collections. I agree that audio and pictures pair beautifully together, and your video of the seasons is inspiring! Wonderful project, thank you for sharing.

      Kate

  4. Oh, I love the sound of nature! I have a few areas I go to nearby, but I can still hear cars and the freeway 🙁 When I am far enough away to just hear the nature sounds, it’s magical!

  5. Very interesting. It would be great to find somewhere that all we could hear is nature. Even the secluded woods I go to is fairly close to a highway. The quietest it gets on my farm is when there is a lot of snow on the ground and it is very cold… :) Thanks for sharing.

  6. Hi Kate, I think your House Wren is more likely a Goldfinch. Love the soundscapes and would love to hear more of your recordings. Maybe make them int a CD?

  7. K- I can’t believe it! I just do things as a hobby. We have a night camera. However, JUST A FEW WEEKS AGO walking the dog late at night, I heard sounds of a bird(?) I could NOT identify and I said to my husband, “We need to be doing audio recordings not just visual!” I LOVE THIS POST!

  8. Fascinating post! I learned something new from this. It makes sense to consider more than one sense in observations, though.

    I loved your last line: “Most importantly though, at least for us prairie appreciators, soundscape ecology reminds us simply to quiet our voices and thoughts so that the prairie, too, might speak.”

    • I love all of the feedback in this comment section, but your second point, quoting Kate, is one that really resonates (sorry, a sort of punny way to put it). I find the term “indoor voices” annoying as a counterpoint to outdoor voices, which I’ve always thought, at least when in natural places, should be softer than elsewhere to the extent possible, so that we and anyone nearby might do as suggested; hear Nature speak.

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