Radiation patterns of a multiple slit system and applications to organ buffet modeling
Résumé
The buffet of an organ encloses a complex field created by thousands pipes acting simultaneously as scatterers and point sources –one in the mouth and one in the passive end, in the majority of cases where the pipe is not stopped. The facade of the organ, otherwise called montre, couples the outside space in the nave with the aforementioned field inside. The main opportunity for field transmission is through the aperture offered by the separation between each of the pipes in the montre. While closed-form models and numerical simulations exist for the transmission through the single slit, the facade of an organ amounts to tens or hundreds of slits thus posing the questions of how to predict the transmitted field and how to group up its behaviour into smaller clusters. An empirically-based approach is followed to provide a description of the field outside the buffet. Measurements were carried at the slit-level and in the near- and farfield radiation space with an experimental scaled model of a positive organ by changing conditions on the number of rigid walls and the density of scatterers. Seeking to validate the filtering effect that the facade has on the incident field, measurements were reproduced in accordance to one set of conditions in the empty buffet of the tribune organ of Notre Dame de Paris. Results from both experiments are compared with predictions.