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By Ed Stiles
July 27, 2007

(Editor's Note: To hear and see the Extinguished Oasis and other instruments made from scrap metal, click on the video link in the box at right.)

A musical instrument made from discarded fire extinguishers proved to be one of the most popular exhibits at this year's Engineering Design Day, an event that showcases projects designed and built by engineering students during the school year.

Few people could pass the instrument's five fire extinguishers without tapping at least one of them to hear the eerie shift in pitch that occurred when they released a foot pedal and lowered the extinguisher into a bucket of water.

Most of the projects at Design Day come from senior design classes, but this musical instrument, called "Extinguished Oasis," was built for an experimental class that brought together students from engineering, music and architecture.

Eighteen students built four instruments for the class, but Extinguished Oasis was the only one displayed at Design Day.

Project Goals
Regina Reed, an Aerospace Engineering student and one of the five students who built the instrument, explained that her team established several goals for its design:

1. The instrument had to be made from scrap metal.
2. It had to have multiple, predictable pitches.
3. It needed to be playable by all five group members at the same time.
4. It had to be easy to master.
5. It had to have a unique sound.

The group salvaged empty fire extinguisher canisters at a local scrap metal yard, cut them into different scoop shapes and suspended them over buckets of water with cables hooked to foot pedals. The canisters ring when they're struck with rubber mallets.

The difference in density between air and water causes the canisters to vibrate at different frequencies as they're lowered into the water.

"We didn't grind the canisters to bring them up to a specific pitch," Reed explained. Instead, the students would strike one of the canisters when it was out of the water and then use a piano to find a matching pitch. They did the same with the canister fully submerged, and this gave them the range of pitches available with each canister.

Performance Notes
"It's difficult to play a scale on this because some canisters have to be in the water and some out, but we can play arpeggios and improvise, rather than playing from sheet music," Reed said.

Other student teams built "Zarp", a harp-like instrument; the "Fire Escape", a set of tuned tanks and fire extinguishers; and the "Happy Accident Perpetual Poolside", a xylophone-like instrument made from a stainless steel pool filter and an oxygen tank. The teams brought their instruments together for a concert at the end of the semester.

The class, "Making Musical Instruments Out of Scrap Metal," was created by Gary Cook, professor of music; Dale Clifford, assistant professor of architecture; and Jeff Goldberg, associate dean of engineering.

Extinguished Oasis was built by aerospace engineering junior Regina Reed, architecture graduate student Matt Gindlesparger, environmental hydrology junior Lisa Wade, mechanical engineering master's student Dan Alfred, and computer engineering senior Tyler Coles.