Influence of Wall Vibrations on the Transient Sound of a Flue Organ Pipe

The question whether the vibrations of a metal flue organ pipe contribute to the perceived sound or not, is still not decided. As one result of the research done in a project within the GOArt (Göteborg Organ Art) center, it has been shown that due to the casting process and the need to save material, the baroque flue organ pipes often have considerably thinner walls than corresponding modern pipes. According to the organ builder, the pipe investigated here is likely to vibrate. To prove the influence of the wall vibration on the perceived sound, recordings of a blown pipe with and without damping of the wall have been carried out. In an accompanying Technical Note in this issue of ACUSTICA – acta acustica, investigations of eigenmodes of the pipe under test using finite element calculations and measurements with force excitation at the labium and sound pressure and velocity measurements with subsequent modal analysis are presented. The results indicate that when this pipe is blown, some structural modes are excited and significantly change some components in the transient spectra of the blown pipe, where as the effect is very small in the stationary spectrum.