3-d sound and spatial audio
DESCRIPTION
3-D Sound and Spatial Audio. MUS_TECH 348. What are Some Options for Creating DTFs?. Pole-Zero Design of Filters. 4th-order filters designed to capture the essential features of HRTFs. Kendall & Rodgers 1982. Pole-Zero Design of Filters. DTFs are created with low computational overhead. - PowerPoint PPT PresentationTRANSCRIPT
3-D Sound and Spatial Audio
MUS_TECH 348
What are Some Options for Creating DTFs?
Pole-Zero Design of Filters
4th-order filters designed to capture the essential features of HRTFs
Kendall & Rodgers 1982
Pole-Zero Design of Filters
DTFs are created with low computational overhead.
Kendall & Rodgers 1982
Pole-Zero Design of Filters
Essential features are encoded in look-up tables.
Kendall & Rodgers 1982
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
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
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.
Principal Components
Novel DTFs can be synthesized from a combination of basis filters, each with a different weight.
Martens 1987
What are the alternatives to Schroeder Crosstalk Cancellation?
“Head Tracked 3D Audio Using Loudspeakers”Bill Gardner
• Head tracking with loudspeakers
• Do crosstalk cancellation below 6kHz
• Designed for computer systems
“Head Tracked 3D Audio Using Loudspeakers”
Q Sound - Pro AudioDanny Lowe and John Lees“Sound Imaging Process” US Patent 5,046,097
Reduction to Practice
Empirical Approach to Design
Q Sound
Results of measurements are consolidated in look-up tables.
How does this work?Crosstalk happens!
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
Q-Sound
What arrives at the ears is the result of the addition.
No crosstalk cancellation!
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.
Similar Approaches Taken By
Cooper-Bauck
Auris (Kendall)
Using other model-based approaches
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
Loudspeaker DTFs Based on Perceptual Model
Path of sound motion degrades gradually with off-center seating.
General Observations(Given a “good” reproduction environment)
What simulated sound locations work most reliably?
Horizontal plane
General Observations
Frontal plane
Distance
Central rear
What simulated sound locations work most reliably?
Sound Examples
http://musictechnology.northwestern.edu/3dsound/gallerytop.html