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Acoustics of a Planetarium

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					  Acoustics of a
   Planetarium
Micah Shepherd, Timothy W. Leishman,
           Utami Sentagi

      Acoustics Research Group
 Department of Physics and Astronomy
      Brigham Young University

150th Meeting of the Acoustical Society of
                 America
            20 October 2005
     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?
               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
                  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
           Predicted Results
front

                             Outline of dome
              Source 1

                                  Star projector




                                    Seat aisles
        Source 2


                         Omnidirectional Source
                 C50
no dome treatment, diffusers

    Source 1 1
     Source
               C50
dome treatment, diffusers

    Source 1
             C50
no dome treatment, diffusers




  Source 2
            C50
dome treatment, diffusers




 Source 2
             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
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
  Measured C50
       (Omni source)


Source 1
 Measured C50
           (Dir source)


Source 1
Measured C50
       (PA system)


Source 1
      Measured C50
           (Omni source)




Source 2
       Measured C50
           (Dir source)




Source 2
           Measured C50
             (PA system)




Source 2
          Other parameters
   STI again very similar to C50
   Average T30: .90 sec
   Fair to good agreement with predicted
    parameters
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
Thank you

				
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posted:6/28/2012
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