1. 3-D Sound and Spatial Audio
MUS_TECH 348
3-D Sound and Spatial Audio

2. Environmental Acoustics and 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. Cathedral / Concert Hall / Theater Sound
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