The pipe organ, with its strong timber base and towering metal pipes, stands as a bastion in concert halls and church sanctuaries. Even when not in use, the pipe organ affects the acoustical environment around it.

Researcher Ashley Snow from the University of Washington sought to understand what effects the world's largest class of musical instrument has on the acoustics of concert halls that house them.

"The question is how much the pipe organ contributes to an acoustic environment -- and the bigger question is, what portion of music is the acoustic environment, and vice versa?" Snow said.

Snow will present data on the sympathetic resonance of pipe organs and its effect on concert hall acoustics on Nov. 20 as part of the virtual 187th Meeting of the Acoustical Society of America, running Nov. 18-22, 2024.

Snow hypothesized that the pipe organ creates an auto-tune effect since its pipes sympathetically resonate to the same frequencies they are tuned to. This effect may enhance the overall musical sound of ensembles that play in concert halls with organs.

A sine-sweep -- a resonance test in which a sine-wave shaped signal is used to excite a system -- was played through loudspeakers facing the organ pipes and measuring the response with a microphone at different positions. Data was gathered by placing microphones inside and around the organ pipes during a musical performance and a church service.

"I was way up in the ranks dangling a probe microphone into the pipes, trying my hardest not to make a sound or fall," Snow said.

Snow verified experimentally that sympathetic resonance does occur in organ pipes during musical performances, speeches, and noises at frequencies that align with musical notes, and that the overall amplitude increases when the signal matches the resonance of one or more pipes.

Investigation into the significance of these effects on the overall quality of musical performance to listeners in the audience is still ongoing. Snow hopes to expand this research by comparing room acoustics between rooms with and without the presence of an organ, along with categorizing and mathematically modeling the tuning system of various world instruments. "What about the sympathy of a marimba, cymbal, or piano strings? Or the mode-locking of horns in a band? Would it sound the same if these things were separated from each other? For better or for worse? I want people to think about that."