Measuring the Organ, Part I: Nervous Breathing and Sensitive Pipes

Carl Johan Bergsten, a research engineer with the Gothenburg Organ Art Center (GOArt) at the University of Göteborg, Sweden, spent the 2011 Thanksgiving holiday studying the wind system and acoustics of Cornell’s baroque organ. The measurements are part of a larger GOArt study exploring the interactions between bellows, wind chest, and pedals to determine an organ’s sound.

One of the sensors next to the pipesThe dynamic behavior of an organ’s wind system is complicated. Stepping on the pedals opens valves that create high and low pressure waves in the air that travels through the system.

It’s necessary to have some reaction in the wind system, though, otherwise the sound is too stiff, explained Bergsten. “You want to hear that the organ is breathing, but if it’s too much it starts to sound nervous and it can be destructive to the organ sound. It’s a delicate balance.”

Bergsten is also measuring how sensitive the pipes are to wind. The better the pipe, the more stable it is to the wind connection, said Bergsten, pointing out that pipes like those used in Cornell’s baroque organ are more stable than ones made by modern methods.

To measure the pressure and the dynamic behavior of the wind system, Bergsten installed four sensors, one each on the Rückpositiv, the Hauptwerk, the Pedal, and the bellows room. He also measured sound from near the pipes and from the floor of the chapel. The sensor system is new; previously, he was only able to measure one pressure at a time.

Bergsten estimated he gathered about 15 gigabytes of data to analyze. “I’m looking for patterns or tendencies,” he said. “We might find something unusual, but we’re interested in overall tendencies as well.” Bergsten plans to return in March and repeat the measurements, to see if there is any difference.