Design and acoustic tests of the ATHENA WFI filter wheel assembly development model towards TRL5

The filter wheel (FW) assembly (FWA), developed by the CBK Institute, is one of the critical subsystems of the wide field imager (WFI) instrument on board the Advanced Telescope for High Energy Astrophysics—mission of the ESA Cosmic Vision 2015-25 space science program (launch scheduled around 2035). The instrument has to collect soft x-rays with very high quantum efficiency, thus WFI requires extremely thin optical blocking filter (OBF). Due to its thickness (∼150 nm) and large area (∼170 mm × 170 mm) needed to achieve a 40 ′ × 40 ′ instrument field of view, the filter is extremely vulnerable to acoustic loads generated during Ariane 6 rocket launch. On the other side, FW mechanism has to provide high overall reliability, so it is more favourable to launch the instrument in atmospheric pressure (without vacuum enclosure for filter protection). Design efforts of the FW subsystem were focused on two issues: providing maximal possible sound pressure level suppression and smallest possible differential pressure across the OBF, which should prevent filters from damaging. We describe the design of a reconfigurable acoustic-demonstrator model (DM) of WFI FWA created for purposes of acoustic testing. Also, the acoustic test campaign is described: test methodology, test criteria, and results discussion and its implication on future FWA design. In general, tests conducted with the FWA DM showed that current design of WFI is feasible and the project can be continued without introducing a vacuum enclosure, which would significantly increase system complexity and mass

Sound Focusing Effects in Horseshoe Plan Theatre

This paper is aimed to study the sound focusing effects in the theatre with horseshoe-shaped plan. It was considered as a case study in the theatre “Vincenzo Bellini” in Catania (Italy), a horseshoe-shaped opera house where both opera and symphonic concerts can take place. This configuration, at the time, was considered to be the best solution for both a good sound quality as well as a good view of the stage for the spectators sitting in the boxes. The geometry of the theatre determines some gaps due to a concentration of the early sound reflections on the back of the room, involving the last rows of seats, thus causing a non-uniform spread of sound in the theatre. This concentration of reflections does not create optimal conditions for good acoustics due to excessive reverberation and negative influence on the listening to music performances