3-D Sound and Spatial Audio MUS_TECH 348. Environmental Acoustics and Computational Simulation.
3-D Sound and Spatial Audio
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Transcript of 3-D Sound and Spatial Audio
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3-D Sound and Spatial Audio
MUS_TECH 348
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What are Some Options for Creating DTFs?
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Pole-Zero Design of Filters
4th-order filters designed to capture the essential features of HRTFs
Kendall & Rodgers 1982
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Pole-Zero Design of Filters
DTFs are created with low computational overhead.
Kendall & Rodgers 1982
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Pole-Zero Design of Filters
Essential features are encoded in look-up tables.
Kendall & Rodgers 1982
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Pole-Zero Design of a Ensemble of DTFs
8th-order filters interactively designed so that poles and zero migrate smoothly between the specified points.
Kendall 1985
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Pole-Zero Design of a Ensemble of DTFs
Filter response is different but the relative pole and zeros positions have shifted in small amounts.
Kendall 1985
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Principal Components Analysis and
Resynthesis Provides an Analytic Approach
to Simplified Filter Design
Martens 1987
PCA Analysis produces a reduced set of ‘basis filters’ that capture all of the significant variation in the data.
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Principal Components
Novel DTFs can be synthesized from a combination of basis filters, each with a different weight.
Martens 1987
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What are the alternatives to Schroeder Crosstalk Cancellation?
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“Head Tracked 3D Audio Using Loudspeakers”Bill Gardner
• Head tracking with loudspeakers• Do crosstalk cancellation below 6kHz• Designed for computer systems
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“Head Tracked 3D Audio Using Loudspeakers”
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Q Sound - Pro AudioDanny Lowe and John Lees
“Sound Imaging Process” US Patent 5,046,097
Reduction to Practice
Empirical Approach to Design
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Q Sound
Results of measurements are consolidated in look-up tables.
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How does this work?Crosstalk happens!
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Sum of two sine waves of the same frequency?
It’s a sine wave: sin(2 π f t + Ø1) + sin(2 π f t + Ø2) =
2 cos[0.5 (Ø1 - Ø2)] sin[2 π f t + 0.5 (Ø1 + Ø2)]
Constant that changesamplitude Sine wave with different phase
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Q-Sound
What arrives at the ears is the result of the addition.
No crosstalk cancellation!
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Q-Sound
Advantages/Disadvantages
• Images not so sensitive to seating position – broader sweet spot
• Listeners can turn their heads toward the image
• Works best with loudspeakers close together
• Difficulty with elevation.• Timbre coloration.
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Similar Approaches Taken By
Cooper-BauckAuris (Kendall)
Using other model-based approaches
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Loudspeaker DTFs Based on Perceptual Model
What loudspeaker signals were required to produce ‘central spectrum’ and ‘interaural disparity’ for a given direction?
Cross talk was incorporated into the computation. The DTFs did not resemble HRTFs.
Kendall 1988
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Loudspeaker DTFs Based on Perceptual Model
Path of sound motion degrades gradually with off-center seating.
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General Observations(Given a “good” reproduction environment)
What simulated sound locations work most reliably?
Horizontal plane
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General Observations
Frontal plane
Distance
Central rear
What simulated sound locations work most reliably?
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Sound Exampleshttp://musictechnology.northwestern.edu/3dsound/gallerytop.html