Capturing the unheard sound of Redwood trees.

We sat down with him to discuss his latest expedition and how his custom-built array of LCT 540 S microphones proved to be a critical tool in capturing the subtle, almost imperceivable, sounds of the redwoods. 

You can listen to the sounds he captured in his latest series of sound libraries from the redwoods in the video below.

Q: Tell us about your work and what you do as a field recordist.

Some field recordists specialize in recording man-made things like guns, cars, and explosions – my expertise is in capturing soundscapes in the natural world. I’ve been doing that for about 10 years with four main categories in mind: storms, glaciers, ancient trees, and whalesong. 

Q: What are some of the unique requirements and challenges you face when recording in these extreme environments?

None of this gear is designed for how I'm using it in the field.

So, it's a lot of figuring out my own techniques that work in extreme environments. How can I power eight LCT 540 S mics to run for 24 hours? How do I keep everything dry in a thunderstorm? How do I protect my mics from wild winds? How do I keep rodents from chewing through my cables? How do I get all the gear to the remote location? How do I get mics up into the canopy of a 260ft Redwood? There's a lot of stuff that I’ve had to figure out and it's been a lot of fun to build my recording skills as well as expertise in expedition planning and logistics. 

Q: Originally, you had reached out to us to try out the LCT 540 S due to its extremely low noise floor, and you wanted to use 8 of them to capture the Redwoods in your latest project. Could you walk us through the process of how you decided on this location and how you figured out how you're going to record it? 

The expedition planning process depends on the scale of the project and can take anywhere from six months on the short end, to something like the Redwoods on the high end, which was a three-year process.

Usually, I'm trying to blend my interest in nature sounds with something that's physically difficult–a blend of field recording and adventure sports. I wanted to climb giant trees to find perspectives in the forest that have not been heard before.

One of the main challenges was to find a location that has old growth Redwoods outside a national park. Only about 5% of the original old growth is left and most of those remaining trees are protected in the parks – and it is almost impossible to get access for tree climbing.

Even researchers struggle with getting these special permissions in Redwoods National Park. 

So my approach was trying to find a privately owned grove that was protected by a conservation group so I could get permission to climb and record in the canopy. I worked with the Sempervirens Fund that protects about 30,000 acres of Redwoods in the Santa Cruz Mountains. 

After that, I had to find a tree climbing guide. There's very few people with that skill set in the world, so it took a lot of research. Eventually, I found someone, got to know him, and built enough trust to feel safe having him take me up into a giant tree.

Q: So, tell us more about the actual recording set up and the challenges during recording.

Let's start with a general overview of what I was trying to do with multiple mic setups. 

Usually I'm going to a location and I'm leaving 6-10 recording rigs (separated by large distances of many miles) for various durations. Depending on the number of mics those drop rigs can run anywhere from 24 hours up to a maximum of seven days.

But this project was different because I was recording with five rigs in a hyper-local part of the forest: vertical points in the same giant tree. I had my giant LEWITT IRT Cross Cube about 1000 ft from the main tree. Another rig was at the right base of the tree. A third rig at 100ft, a fourth at 175 ft, and a final 4.0.2 rig in the canopy at 225 ft! So I ended up with this ridiculous setup of vertical ambience layers. 

This technique enables you to hear, for example, the same raven call from multiple perspectives throughout the same tree! These trees are so tall that they have distinct micro-ecosystems within them that each have a unique acoustic character. Later this year I’ll be releasing a library that showcases this recording technique–Redwoods: Vertical Ambiences. 

Q: What were your experiences with the LCT 540 S, and what problems did it solve?

You wouldn’t need the specs of the LCT 540 S to record in a loud environment like a jungle. But the low self noise and high sensitivity of this mics is essential in sparse and extremely quiet environments like Redwood forests. 

I was experimenting with various immersive audio mic arrays in the Redwoods because there's a very strong vertical component to these forests. Many of these trees don't have any branches until 150 feet up! I built an IRT Cross Cube of eight LCT 540 S mics to capture this 3D soundscape. It was a difficult technical challenge to get it all set up in the field, but I made it work with some DIY mounting brackets, furry windscreens, an overloaded tripod, and some prayers for no rain. 

To build an IRT Cross Cube, you start with two IRT Cross setups, one stacked on top of the other. The mics are about 25 cm apart in a square, and they're all facing 90° from each other. There's a bottom quad and a top quad, and that makes a cube that's 25 cm x 25 cm x 25 cm. Those eight mics give you a fabulous immersive audio setup that is unmatched in its ability to record in almost-silent environments. 

To capture the subtle sounds of these trees in all its detail, you need something that is as ridiculously quiet and sensitive as the LCT 540 S. Otherwise you just end up hearing the self noise of the microphones. 

Redwood “needle rain” is something that is almost imperceptible to the naked ear.

There's not a lot of mics that can capture sound that’s below the threshold of human hearing. Pairing those mics with great preamps and I had a “sound telescope”. Then, all of a sudden I heard thousands of needles falling. I thought it was raining at first and couldn't figure out what was making this precipitation-like sound. After talking with a Redwood researcher I found out that these trees shed needles in the spring and with just the slightest of wind gusts tens of thousands of needles break loose and fall with delicate and wonderfully soothing sounds. I love the subtle sounds of almost-silent spaces and this is one of my favorites. 

Listen to the sound sample below.
 

Q: That's super interesting! Have you had any other unexpected, unique sound discoveries in the Redwoods?

One of the great things about recording continuously for long periods of time is that I often capture unexpected moments. One of my favorite sounds from the project was a giant Redwood tree falling in the distance.

Imagine a completely quiet night and then a giant bomb going off in the distance as the tree falls, and then it reverberates through the valley. That was really captivating to hear. 

Another was vibrations from inside the wood itself. I was recording with two contact mics that were stuck into the bark of the tree. I was trying to capture the sound of water being sucked up through the Xylem of the tree, which is the living part of the tree behind the bark. That's supposed to make a subtle bubbling sort of sound that I believe I captured, but I have to confirm with a scientist.  

While trying to capture the sound of water moving through the xylem, another fascinating thing happened. I was recording in parallel with two LCT 540 S mics, plus the two contact mics embedded in the bark. As I was listening I suddenly heard a raven through the contact microphones!

I was surprised when I heard the raven, and couldn’t believe what was happening. I thought I was listening to the contact mics and wouldn’t be able to hear any wildlife. However, if the wildlife is loud enough, and low enough frequency (like raven or owl calls) it will vibrate the wood. So, the raven call was vibrating the tree and then this thousand-year-old wood was acting as a filter to bring out the Redwood resonance. You are hearing what the tree feels, and that is fascinating. 

You can hear the Redwood treefall and inside the tree here: AM88 Redwoods: Inside the Tree

Overall, for this project, I was interested in the sounds of the trees themselves. The old-growth tree as the subject. Not the wildlife, like most nature recordists focus on. With incredibly quiet mics you can hear things like the bark creaking as the temperature changes throughout the day and the sci-fi whooshing of a branch cutting through the air as it falls from 200 ft above. 

Wow. It sounds like you capture a lot of interesting and unexpected sounds out there.

Yes, it was a wonderful adventure that fulfilled my boyhood dream of climbing a Redwood tree! I’m very excited to share the 3D recordings I made and I can’t wait for listeners to be transported to these ancient wooden cathedrals they might never have the chance to visit. 

If you enjoyed these sounds and stories, there’s another layer to this project where I hauled some Genelec speakers into the forest and set up a sound art installation based on feedback loops. Here's a behind the scenes min-doc with a nature album at the end. 

Redwood Resonance: Genelec x Thomas Rex Beverly – A Resonant Collaboration Rooted in Nature

If you want to learn more about Thomas Rex Beverly’s work and explore his nature sound libraries visit https://thomasrexbeverly.com/ 

And if you were inspired by this project, please consider donating to the Sempervirens Fund to help preserve the soundscapes of these ancient trees. For more information about the fund, visit: https://sempervirens.org/