Examination of the reflection properties of sloping terminations to organ pipes

The sound characteristics of both labial and lingual organ pipes are affected to a great extent by the reflection properties of the resonators. In this paper, the reflection properties of sloped pipe terminations are examined and the possible applications in organ building practice are investigated. Sloped shallots of reed organ pipes with different termination angles are of particular interest in this study. For the examination of the reflection properties two different approaches are applied. Sound pulse reflection measurements on model geometries provide experimental data in the time domain, while finite element simulations yield reflection coefficients in the frequency domain. These two remarkably different approaches are shown to provide consistent results for all examined geometries. Laboratory measurements performed on experimental labial pipes and "Trompete" (trumpet) shallots demonstrate some of the effects of sloped terminations on the sound of organ pipes and validate the applicability of the results obtained by the model measurements and simulations.