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Spark Photo of Sound Waves in Model of Holy Trinity Church, Buffalo, New York, Before Correction by Paul E. Sabine
  • Spark Photo of Sound Waves in Model of Holy Trinity Church, Buffalo, New York, Before Correction, c. 1913
  • Paul E. Sabine
  • Lantern slide
  • National Museum of American History, Behring Center
  • Physical Sciences Collection
  • Image No. 255,934.03

Spark or Shadow photographs, developed by Harvard professor, Paul E. Sabine, show the progress of a single sound wave as it travels through a model space. Sabine used them to make pioneering studies of architectural acoustics. In this photograph, he created a cross-sectioned miniature of an auditorium. Using the sharp snap of an electric spark, he produced a sound wave from the position of the stage. A small fraction of a second later, a distant second spark illuminated the entire scene and created an image of the position of the wave. The spark apparatus that produced the sound waves was adjusted so that the model wave was in the same scale as a real sound wave in a real auditorium. Multiple reflected waves in the models corresponded to annoying reverberations in the real spaces. While these photographs are generally presented as images of sound waves, the image is actually caused by a change of density in the air as the sound wave travels through it. Much like a lens, this dense air refracts the light and produces a band of light and shadow that reveals the presence and position of the wave. Because of the wave's optical effect, this type of photography did not require a camera. The model was simply placed on a photographic plate in a dark room and the illuminating spark created an image by projection.

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