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3-D Sound and Spatial Audio

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.

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3-D Sound and Spatial Audio

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  1. 3-D Sound and Spatial Audio MUS_TECH 348

  2. What are Some Options for Creating DTFs?

  3. Pole-Zero Design of Filters 4th-order filters designed to capture the essential features of HRTFs Kendall & Rodgers 1982

  4. Pole-Zero Design of Filters DTFs are created with low computational overhead. Kendall & Rodgers 1982

  5. Pole-Zero Design of Filters Essential features are encoded in look-up tables. Kendall & Rodgers 1982

  6. 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

  7. 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

  8. Principal Components Analysis and Resynthesis Provides an Analytic Approach to Simplified Filter Design PCA Analysis produces a reduced set of ‘basis filters’ that capture all of the significant variation in the data. Martens 1987

  9. Principal Components Novel DTFs can be synthesized from a combination of basis filters, each with a different weight. Martens 1987

  10. What are the alternatives to Schroeder Crosstalk Cancellation?

  11. “Head Tracked 3D Audio Using Loudspeakers”Bill Gardner • Head tracking with loudspeakers • Do crosstalk cancellation below 6kHz • Designed for computer systems

  12. “Head Tracked 3D Audio Using Loudspeakers”

  13. Q Sound - Pro AudioDanny Lowe and John Lees “Sound Imaging Process” US Patent 5,046,097 Reduction to Practice Empirical Approach to Design

  14. Q Sound Results of measurements are consolidated in look-up tables.

  15. How does this work?Crosstalk happens!

  16. 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 changes amplitude Sine wave with different phase

  17. Q-Sound What arrives at the ears is the result of the addition. No crosstalk cancellation!

  18. Q-SoundAdvantages/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.

  19. Similar Approaches Taken By Cooper-Bauck Auris (Kendall) Using other model-based approaches

  20. 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

  21. Loudspeaker DTFs Based on Perceptual Model Path of sound motion degrades gradually with off-center seating.

  22. General Observations(Given a “good” reproduction environment) Horizontal plane What simulated sound locations work most reliably?

  23. General Observations What simulated sound locations work most reliably? Distance Frontal plane Central rear

  24. Sound Examples http://musictechnology.northwestern.edu/3dsound/gallerytop.html

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