3-D Sound and Spatial Audio

MUS_TECH 348

Environmental Acousticsand Perception

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.

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.

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

Subjective Preferences for Concert Halls

Rasch and Plomp discuss how spaciousness, a desirable property, is captured in the ratio of indirect to direct sound.

Subjective Preferences for Concert Halls

Key questions arise about the relative importance of indirect sound coming from the side walls, ceiling and rear wall.

Subjective Preferences for Concert Halls

Rasch and Plomp report how synthetic indirect sound can be manipulated for experimental purposes.

Subjective Preferences for Concert Halls

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The direction from which indirect sound arrives has a strong impact on the similarity of the energy arriving at the ears.

Side wall reflections Ceiling, rear wall and floor reflections

The subject quality of “spaciousness”:• Feeling surrounded in sound• Sound has no particular location• Sound occupies a volume of space• “Immersion”

Subjective Preferences for Concert Halls

Spaciousness depends on interaural incoherence.

Acoustic Diffusion of Indirect Sound

Good Bad

Concert hall design should attempt to create interaural incoherence in the indirect sound.

Acoustic Diffusion of Indirect Sound

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1D and 2D QuadradicResidue Diffusers (QRDs) invented by Schroeder.

terminology:

Cathedral / Concert Hall / Theater Sound

Altar / Stage / Screen

Spiritual / EmotionalWorld

Subjective

MusicAmbience

Cultural Context of Spaciousness

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