What is the sound of terra cotta, and can we manipulate it to enhance the experience of a space?

Today's urban spaces are loud. Increased car and air traffic can bring the ambient noise to 60-85 decibels, levels at which long-term exposure can cause hearing damage, among other negative outcomes. Traditional psychoacoustic approaches usually focus on creating sound-neutral environments to manage noise pollution, but we were interested in how architecture, specifically constructed from terra cotta, could enhance the experience of a space. We wanted to charge a space with a vitality that transforms it into something more serene, content-rich, and akin to what many people associate with being out in the natural world, so we created an instrument that could do that. 
For the 2019 Architectural Ceramic Assemblies Workshop at the University at Buffalo, our investigation culminated in a terra cotta soundscape with composer Joshua Stamper, called Silo Silo.

The research team installed, played, and recorded Silo Silo inside the defunct grain elevators of Silo City in Buffalo, New York. We chose this site for the performance because of the silos' acoustics and striking resemblance to our instrument's terra cotta cylinders.


To make this instrument and composed piece, the research team had to consider four primary variables: soundscape strategy, component design, component fabrication, and field activation. In this process, the research team created and assessed a series of hollow, terra cotta cylinders that produced sound when struck from the inside with a hammer.  
Early on we decided to work with the cylinder as an archetype form and envisioned a stand of them, like a birch forest of slender, elegant terra cotta tree trunks, that would be both physically unimposing and playful in nature. We made two decisions to structure our investigation: first, we would use mechanical mallets within the cylinders to strike, brush, or scrape the terra cotta and create sound, and second, the interior profile of the cylinders would be articulated to add nuance and create sonic variance.  
Through studying the sounds produced by different configurations of the terra cotta cylinders, we eventually created a percussive instrument out of the material. The site of the instrument installation—Silo City in Buffalo, New York—has fascinated many historic figures including Le Corbusier, Walter Gropius, and Erich Mendelsohn. The silos' acoustics made this a natural choice for the performance. 

A line diagram of the components inside each cylinder of the instrument, as well as a diagram of the branches in formation.

A drawing produced in a brainstorming session showing possible ways to manipulate the terra cotta shapes.

Bells, Twinkles, and Food Processors

The team prototyped, tested, and tuned the cylinders to create different qualities of sound. Using water-jet-cutting technology to cut precise forms, the interior of the cylinders were articulated with ridges, bends, notches. Using piezo microphones and other audio equipment, the research team tested each cylinder with whisks, dowels, wire brushes, wooden and metal mallets. Some sounds were “bell-like” while others “twinkled” or sounded like a food processor or rotary phone. Some hammer-and-cylinder combinations produced no noise at all, or simply would not fit together.  
Each cylinder and sound generator combination was recorded, reviewed, and cataloged with the goal of understanding the possibilities of this material. In this process, many of the cylinders needed to be remade and tested in different combinations. 

Once categorized, the team combined individual components into an instrument for performance. Composer Joshua Stamper arranged a composition and, the team rehearsed the composition with Stamper before breaking down and re-assembling the instrument in Silo City.  
This instrument is a proof-of-concept towards incorporating terra cotta into modern urban spaces: Its soothing sounds could provide respite and interaction for the public.