3-D Sound and Spatial Audio

1. 3-D Sound and Spatial Audio MUS_TECH 348

2. Intensity Panning with Loudspeakers

3. Stereo Law of Sines sin (ß) / sin (q) = (L - R ) / (L + R) Where ß is the angle of the virtual image and q is the angle of the loudspeaker from center “Phaser Analysis of Some Stereophonic Phenomena” Ben Bauer 1961

4. By the way, just HOW does panning work? L R Panning with stereo loudspeakers includes crosstalk!

5. a a t t a t Consider sine waves! a t L R Panning results in amplitude and phase difference!

6. Consider sine waves! L sin (2p f t) R sin (2p f t) k (<1) and ø are constant for fixed loudspeaker & listener locations L sin (2p f t) + kR sin (2p f t + ø) L * R --- delayed (ø ) and reduced in gain (k) * + t t = t

7. Consider sine waves! a t a t L R R sin (2p f t) + kL sin (2p f t + ø) L sin (2p f t) + kR sin (2p f t + ø) What about the resulting IID and ITD?

8. a t Consider sine waves! a t L R ( L2 + k2R2 + 2 kLR cos (- ø) ) IID(in decibels) = 10 log (k2L2 + R2 + 2 kLR cos (- ø) ) L sin(2pft) + R sin(2pft+ ø) L cos(2pft) + R cos(2pft+ ø) Interaural phase = arctan R and L affect the IID and interaural phase!

9. Panning Methods 0.5 amp Amplitude Panning L (C) R position 0.7 Intensity or Power Panning amp L (C) R position

10. Panning Methods Near-field Monitoring: Greatest accuracy: Low Frequencies: amplitude panning High Frequencies: power panning Large-space Monitoring: power panning

11. Panning Inaccuracy High Low L (C) R position

12. How well does panning work in typical multichannel settings like 5.1? L C R S1 S2 S1 S2 S1 S2 S1 S2

13. ITD / IID HRTF For side locations the only change is a cross fading of HRTFs! Cross fading does not produce proper HRTFs in the middle! HRTF only HRTF ITD / IID