Understanding Acoustics and Spatial Audio in Concert Halls

1. 3-D Sound and Spatial Audio MUS_TECH 348

2. Environmental Acousticsand Perception

3. Subjective Preferences for Concert Halls Schroeder’s work led to the understanding of the importance of side reflections and the decorrelation of the late field. There are four significant dimensions in preference judgments. Two are represented here. Numbers represent listeners and Capital letters are concert halls. Halls H, K and J are most preferred.

4. Subjective Preferences for Concert Halls “Initial reverberation time” (T) is highly correlated to preference D1 and “definition” is negatively correlated. These are somewhat inversely related. Other factors with negative correlation are: “width of hall” (W) and “interaural coherence” (C). People appear to prefer longer reverberation times, narrower halls and low interaural coherence.

5. Subjective Preferences for Concert Halls • Rasch and Plomp summarize studies that describe three subjective qualities: • Loudness---perceived loudness • Definition---ability to distinguish and recognize sounds, negatively correlated with indirect sound • Spaciousness---sense of being surrounded, positively correlated with indirect sound

6. Subjective Preferences for Concert Halls Rasch and Plomp discuss how spaciousness, a desirable property, is captured in the ratio of indirect to direct sound.

7. Subjective Preferences for Concert Halls Key questions arise about the relative importance of indirect sound coming from the side walls, ceiling and rear wall.

8. Subjective Preferences for Concert Halls Rasch and Plomp report how synthetic indirect sound can be manipulated for experimental purposes.

9. Subjective Preferences for Concert Halls Ceiling, rear wall and floor reflections Side wall reflections The direction from which indirect sound arrives has a strong impact on the similarity of the energy arriving at the ears.

10. Subjective Preferences for Concert Halls The subject quality of “spaciousness”: • Feeling surrounded in sound • Sound has no particular location • Sound occupies a volume of space • “Immersion” Spaciousness depends on interaural incoherence.

11. Acoustic Diffusion of Indirect Sound Concert hall design should attempt to create interaural incoherence in the indirect sound. Good Bad

12. Acoustic Diffusion of Indirect Sound terminology: 1D and 2D Quadradic Residue Diffusers (QRDs) invented by Schroeder.

13. Cultural Context of Spaciousness Cathedral / Concert Hall / Theater Sound Altar / Stage / Screen Spiritual / Emotional World Subjective Music Ambience

14. Artistic Uses • Connection to magical/spiritual/emotional world • Give impression of space beyond the visual frame • Create separate acoustic space for music and listener’s emotional world