Experimental studies of the influence of structural properties of flue organ pipe walls on its transient sound characteristics

Övrigt konferensbidrag, 2004

Recently, the influence of structural vibrations on the sound quality of flue organ pipes has been the subject of many investigations. Most work has been done on the coupling between body and enclosed oscillating air column. Being in immediate contact with the jet, the upper labium could influence the jet's oscillation and thus play an important role during the beginning transient, too. However, this latter issue has not been investigated intensively yet. In this paper the question of feedback from the vibrating upper labium on the jet oscillations is addressed. In this context the structural properties of the upper labia are of great importance. Beside thickness and material the shape and the transition from labium to body might play a role. Non-contact measurements in the frequency and time domain show different vibration qualities for different labia shapes. Overblowing the flue organ pipes it is found, that for one kind of labium initially the body is excited through the labium and only when the tone becomes stable this excitation is taken over by the internal standing waves. Further, a very thin-walled pipe has been investigated. No significant clues could be found yet, although the pipe tended to large structural vibrations. Therefore it remains open, whether the vibrations of the labium can influence the jet's oscillation by feedback.