Thank you to the TreeHouse residency for original inspiration, Kristi Head for help with concept development, Dagtronix for circuit optimization, Grey’s Anatomy for source image, Josh Plotkin for sound recording, Automata for CNC and laser help, John Rice for wood jig help, Sarah Shebaro for screenprinting tutorial, and Daniel Gross and Emma Judkins for help with assembly.
The idea for TreeShell started when I was living in the woods of the Upper Adirondacks as part of the TreeHouse residency. While listening to the wind in the trees and the birds and rain, I thought of how people often bring back photographs as memories of a place, but rarely sounds. What if there was a way to relive that experience once I was back in the city? Children often listen to seashells and imagine the sound of the ocean. I wanted to make a piece of a tree play back the sound of the forest.
I started with a birch tree, cut a disc that could be comfortably held in the hand, and hollowed out the inside to hide some electronics in. My first prototype used a commercial MP3 player chip and a tiny mechanical pin switch that depressed when the object was set on a surface. When the switch was released, the sound player turned on. This worked but had a few disadvantages. The first was the sound started over every time it was picked up. I thought it was important to have a sense of a narrative that resumed wherever you left it, kind of like picking up a book again. Even though the sound is quite ambient, you quickly recognize the same passage, and it would be a special and rare feature to continue hours or even days later. The second disadvantage was the delay until starting was quite long, unless it was kept in pause mode, but this burned the battery too quickly. I started working on designing my own circuit.
To machine the inside of each piece I first used two large forstner bits, the larger one cut a small lip that the inset disc could sit on. I wanted a visible inset so that the underside would suggest an old telephone receiver and subtly suggest a speaker or sound. I didn’t want anything else visible to give away what was inside. Ideally it would be discovered intuitively. The only concession to this was cutting a tiny hole for a USB port so the battery could be recharged using the same cables many people use for cellphones. No power adaptor is necessary, just any USB port, even an iPhone charger. I decided against any status or charging LEDs for the same reasons.
The second and third versions got progressively smaller; I wanted children to be able to easily hold the object in one hand. As the tolerances got tighter, I started using a CNC mill to cut out the interiors and USB port. The port in particular was very difficult since it was very small but needed to be deep enough to pass through the wall thickness, which in some cases was 3/4”. I ended up using a combination of CNC and router and dremel jigs to get the precision I needed.
The image on the top was adapted from a 19th century engraving in the famous book Gray’s Anatomy. I considered stamping it but then progressed to a computer-controlled laser etching process. If the settings are exactly right, the laser burns the image in, producing a lovely natural sepia tone without losing detail. I liked updating this antique illustration with modern techniques, although it required many hours of digital retouching and testing with various powers and speeds of the laser.
The final circuit went through 14 modifications before it performed how I wanted it. I had to make some compromises on response time to get the battery to last long enough that recharging was rarely required. I also tweaked the volume carefully so that it was loud enough to hear but quiet enough that it required being held close to the ear, which had a privacy and intimacy I liked. Enabling the piece to resume the soundscape from where you left it was critical. The sound chip on the board was limited and I decided with a heavy heart to discard the entire design and start over. Dennis Greenwood at Dagtronix redesigned my circuit using a different microcontroller which had faster response time and better battery life.
The boards were populated by hand using a stainless steel solder paste stencil, a DIY suction tool, and a toaster oven electronically controlled for solder reflow. The oven controller was an Arduino-compatible RefloLeo whose code I modified. The suction tool was made from a modified aquarium pump and a syringe and works better than tweezers for placement of 0603 parts (0.06” x 0.03”, 1/3 the size of a grain of rice!). Reflow worked well but the precision of solder paste application and part placement with 0.5mm pitch QFN components was critical. I used an inexpensive microscope with 30x magnification to be sure parts were not misaligned or had bridged pins.
The assembled pieces were finished with a natural shellac made from beetle shells and denatured alcohol. The ratio was important, too dark and the image contrast was reduced and the piece was too shiny, too little and it wasn’t protected from dirt and other wear. Most other commercial finishes were not matte enough, or darkened the wood too much. The small discs that cover the electronics were made from the same tree segment as each piece. A long cylinder was turned down on a lathe to within 0.01” tolerance and then sliced into 1/8” segments using a parting tool. The discs had to be thick enough to resist breakage but thin enough to allow sound to pass through without requiring perforation. It turned out the resonance of the hollow interior provided natural amplification so a very low power circuit could be used.
For the packaging I went through many different materials and shapes. I ended up using a simple recycled cardboard box that was heavy enough to be shipped on its own. The box folds together from a flat sheet using no adhesive or tape. The image and text on the box was screenprinted by hand and came out quite well. The packing fill is also made from recycled material. Although it cost more to hand-make all the boxes, I thought some people would choose to keep them and it was worth being nice enough to not be immediately thrown out like most boxes. In the end I was proud to use local materials and production for every step of the project. The trees come from the border of New York and Pennsylvania. The machining was done in Brookyln and Long Island City. The laser was done in downtown Manhattan and Long Island City. The circuit design was done in upstate New York. The packaging was done in Fort Greene, Brooklyn. The final assembly was done in the Brooklyn Navy Yard at my studio.
This was my first attempt at transforming an art object into a mass manufactured design piece. Although it looks simple, it took well over a year to design and produce. Many thanks to the MoMA Design Store jury for choosing TreeShell as one of the representatives of innovative design in New York.