1. Acoustics of a Planetarium Micah Shepherd, Timothy W. Leishman, Utami Sentagi Acoustics Research Group Department of Physics and Astronomy Brigham Young University 150 th Meeting of the Acoustical Society of America 20 October 2005

2. Summerhays Planetarium Located on the Brigham Young University campus Recently renovated Serves as a planetarium and classroom Seating capacity: 119 Dome radius: 38’ Ziess zkp3 star projector Good classroom acoustics?

3. Overview Motives: Astronomy faculty and Summerhays Planetarium supervisor desired good classroom acoustics I. Acoustic recommendations given and implemented II. Room acoustic measurements taken after construction completed

4. Acoustic Modeling CAD drawings made in EASE ® Dome modeled using 303 Planar faces Dome treatments: Hard surface 2.68” BASWAphon ® smooth, even finish Side wall treatments: Gypsum board Alternating absorptive panels RPG diffusors Room parameters T30, C50, STI calculated and analyzed

5. Predicted Results Outline of dome front Source 1 Source 2 Seat aisles Star projector Omnidirectional Source

6. C50 no dome treatment, diffusers Source 1

7. C50 dome treatment, diffusers Source 1

8. C50 no dome treatment, diffusers Source 2

9. C50 dome treatment, diffusers Source 2

10. Other parameters STI results very similar to C50 results Average T30 1.8 sec no dome treatment 1.1 sec dome treatment Listening tests using auralizations Room treatment found to be necessary for good intelligibility Dome treatment and alternating absorptive/ reflective wall panels were recommended, accepted and implemented

11. Room Measurements 23 receiver locations 2 source locations Lecture podiums in front and back of room Dodecahedron source Single driver active All drivers active PA system 2 EAW dsa-250 (digitally steerable arrays) Directional source with microphone

12. Measured C50 (Omni source) Source 1

13. Measured C50 (Dir source) Source 1

14. Measured C50 (PA system) Source 1

15. Measured C50 (Omni source) Source 2

16. Measured C50 (Dir source) Source 2

17. Measured C50 (PA system) Source 2

18. Other parameters STI again very similar to C50 Average T30:.90 sec Fair to good agreement with predicted parameters

19. Conclusions BASWAphon can partially control unwanted reflections from a planetarium dome while providing an excellent projection surface Directional loudspeaker arrays keep sound out of the dome and therefore improve speech intelligibility With appropriate acoustical planning, planetariums can also function as classrooms Planetarium users are very pleased with the acoustics of the Summerhays Planetarium

20. Thank you