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Acoustics of a large immersive environment The Allosphere
Acoustics of a large immersive environment environment, The Allosphere The Allosphere is a new audio/visual immersion space for the California Nanosystems y Institute at the Universityy of California, Santa Barbara, used for both scientific and performing arts studies. This 3-story sphere with centralaxis catwalk permits an unusually large experiential region. The huge perforated-metal visual-projection sphere, with its principle listening locations centered inside the sphere, introduces multiple considerations and compromises, especiallyy since the ideal acoustical environment is anechoic. Video projection requires opaque light reflectivity of the concave projection surface, while audio solicits extreme sound transmissibility of the screen plus full-range sound absorptivity outside the sphere. The design requires highfidelity spatialization of a large number of simulated sound sources over a large region near the core, and support of vector-based amplitude panning, Ambisonic playback, and wave-field synthesis. This paper discusses considerations that both conform to, and lie outside of, traditional acoustical analysis methodologies, and briefly reviews the h electroacoustic l i systems design. d i D. Conant, W. Chu, R. Silva, T. McNally, G. Sparks, K.A. Hoover/ McKay Conant Hoover Inc. & S. Pope/U.C. Santa Barbara Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 The Allosphere Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Allosphere Space and Applications Perforated, aluminum sphere: -Light-reflective & sound-transmissive -Ten meters in diameter ((3-stories tall)) -Within a highly-absorptive chamber (4-stories tall) Next-generation immersive interface: -Synthesis, y manipulation, and analysis y of large-scale g data sets -Virtually-real sensorial perception -Multi-user interactive interfaces -Stereo-optic video projection on the entire inside of the sphere -Multi-channel audio playback Research: -Rendering, visualization, and “sonification” -Data mining and navigation of complex, dynamic data sets -Interaction with complex displays -System integration for distributed real-time systems -Large-scale spatial audio rendering Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 SPHERE V = 645 m3 / 22,790 ft3 A = 457 m2 / 4,920 ft2 FULL ROOM V = 1,860 1 860 m3 / 65,650 65 650 ft3 A = 10,55 m2 / 11,350 ft2 Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Electro-acoustic System Summary Goals: -place virtual sound sources at arbitrary points in space -simulate acoustics of spaces with high accuracy Techniques of spatial sound reproduction: -VBAP (Vector-based amplitude panning) – locating a sound source within a g the balance of the audio signal g for each speaker space byy setting -Ambisonic spatialization – encoding sound sources and their geometry, and decoding them using exclusive transforms -Wavefield synthesis – recreating wave fronts with large & dense loudspeaker arrays, based on superposition Acoustical requirements (for proper operation): -Quiet: Quiet: < NC 20 -Maximum T60: 0.75 s, 100 Hz to 10,000 Hz -Sound-transparent screen Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Background Lp (measured) Leq Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 GLASS FIBER WEDGES CEILING & WALLS (2ft / 0 0.6M) 6M) 23% PERF SCREEN Surfaces 32ft / 9.75M SECTION MID-LEVEL PLAN Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Above sphere 4 inch fuzz where wedges not possible 4-inch UPPER PLAN Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 GLASS FIBER WEDGES CEILING & WALLS (2ft / 0 0.6M) 6M) 23% PERF SCREEN Loudspeakers M-Audio BX8a loudspeaker 32ft / 9.75M SECTION MID-LEVEL PLAN Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Perforated Screen Close-up Close up REALLY Close-up Close up Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 T60 Calculation Summary Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 T60, Predicted INITIAL PREDICTED REVERBERATION TIME Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Measurements Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Measurement System Summary Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Measurement System Summary & SWEPT SINE Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Measurement System Summary Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 T60, Measured using sine sweep Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 T60, Measured using balloons BALLOON POPS Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Balloon Burst Lp @ 10ft Overblown: 93dBA, 95dBC Pin pricked: 89dBA, 88dBC Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Balloon Burst Lp @ 15ft Overblown: 87dBA, 91dBC Pin pricked: 86dBA, 85dBC Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 T60, Measured using pink noise STOPPED PINK NOISE BALLOON POPS Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 T60, Comparison STOPPED PINK NOISE PREDICTED BALLOON POPS Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Perforated metal: reflection & attenuation Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 FIRST ARRIVAL Inside 5kHz 1/3 OCTAVE SPHERE REFLECTION 12dB Outside Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 10kHz 1/3 OCTAVE FIRST ARRIVAL Inside SPHERE REFLECTION 6dB Outside Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 FIRST ARRIVAL Inside 5kHz 1/3 OCTAVE SPHERE REFLECTION 2.8msec Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 12dB 10kHz 1/3 OCTAVE FIRST ARRIVAL Inside 6dB SPHERE REFLECTION 2.8msec Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Due to T. Schultz, 19866 Perforated Metal Acoustical Transparency Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Due to T. Schultz, 19866 Perforated Metal Acoustical Transparency . 0.5dB A 5 kHz Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Due to T. Schultz, 19866 Perforated Metal Acoustical Transparency . 2.0dB A 10 kHz Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 A = Perf. Metal Attenuation, dB Di Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 A = Perf. Metal Attenuation, dB Di for 4ft x 4ft Flat Segments Li Lr Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Dr A = Perf. Metal Attenuation, dB Di Li Lr Dr 5kHz 10kHz A = 0.5dB ; 2.0dB Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 A = Perf. Metal Attenuation, dB Di Li Lr Dr 5kHz 10kHz A= 0.5dB ; 2.0dB Meas.Refl.= -12.0dB ; - 6.0dB Calc. Refl. = -11.4dB ; - 6.1dB Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 Reverberation Time, Comparison STOPPED PINK NOISE PREDICTED BALLOON POPS INFERRED FROM SINGLE REFLECTION i.e. NEAR-FIELD, PERFORATED METAL ONLY Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 OBSERVATIONS & CONCLUSIONS T60 = 0.40 - 0.50 sec, from 63 Hz - 4 kHz, predicted & measured. T60 is highly uniform, irrespective of the measurement method (swept sine, stopped t d noise, i b ll balloon pops)) and d source location(s), l ti ( ) including i l di widely id l separated synchronous sources. g reflections approximates pp measured T60 at 8 kHz . T60 inferred from single The space’s sound is comfortable, and focusing is challenging to discern. Audio & visual localization tracked together convincingly . Subjectively, the 23% perforated metal offered negligible sound absorptivity or reflectivity, as assessed in the normal observation areas of the catwalk. Schultz’s perforated metal attenuation, A, is supported by experiment. A is negligible for this screen (which also supports visual visual-image image projection). projection) Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008 In Appreciation pp Theodore J. Schultz, Ph.D. “Acoustical Acoustical uses for perforated metals: Principals and Applications”, Applications” 1986, 1986 Industrial Perforators Association (Library of Congress catalog card # 86-147993) JoAnn Kuchera-Morin, U.C. Santa Barbara Technical Committee on Architectural Acoustics of the ASA Acoustics of a large immersive environment, The Allosphere Paris, 155th ASA, 30 June, 2008
