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Improved 3D Sound Delivered to Headphones Using Wavelets

Improved 3D Sound Delivered to Headphones Using Wavelets. By Ozlem KALINLI. EE-Systems University of Southern California December 4, 2003. Outline:. Introduction Work Results Conclusion. Introduction. Immersive Audio Environments. Transport listener into the

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Improved 3D Sound Delivered to Headphones Using Wavelets

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  1. Improved 3D Sound Deliveredto Headphones Using Wavelets By Ozlem KALINLI EE-Systems University of Southern California December 4, 2003

  2. Outline: • Introduction • Work • Results • Conclusion

  3. Introduction Immersive Audio Environments • Transport listener into the same sonic environment as the event • Multiple, spatially-distributed sound sources • Head and source motion • Room Acoustics • Virtually listening environments • Synthetic acoustic images (headphones or loudspeakers) • Simulated directional sound information • Simulated room acoustics Immersive Reproduction of 3D Sound Scheme

  4. Introduction Head Related Transfer Function (HRTF) • Head Related Transfer Function (HRTF) Special transformation of a source from a point in free space to the listener’s eardrums. • HRTF measurements are computed using a dummy head (KEMAR) • Used for sound localization Sound Transmission from Source to Listener

  5. Introduction Sound Localization • Localization of sound, cues: • Interaural time difference (ITD) , dominant below 1.5 kHz • Interaural intensity difference (IID), dominant above 3 kHz • Reasons: • Path length difference • Head Shadowing • Reflection of Head

  6. Work Main Work • Goal of Work: To obtain a better sound diffusion from the mono-sound recorded at an anechoic chamber • System Tools • Use HRTF to localize sound, 30o azimuth, and 0o elevation • Use wavelet filter banks with time delay at the lowest frequency (below 1.5 kHz) to get the sound diffusion (adding reverberant sound)

  7. Work Overall System • Fs= 44.1 kHz, 16 bit • 5 Stages of dyadic tree to get the signal below 1.5 kHz • Daubechies wavelets, with filter tap 16 • Delay time 7.25 ms

  8. Results Simulation Results • 4 different types of audio signals are tested Piano, guitar, classical music, pop song • Time Domain Waveforms for Piano Sound (Left Channel) (a) HRTF Sound (b) Delayed Sound with Wavelet (c) Final Sound

  9. Results Results for Piano Sound • Subjective Listening Tests • Relation Between Time Delays and Correlation Coefficient

  10. Results Other Work Done • Sound localized at 110o of azimuth with 0o elevation is also tested, since surround sound is desired at the + 110o and - 110o • Listening test results similar to the 30o of azimuth • Relation Between Time Delays and Correlation Coefficient

  11. Results Results for Piano Sound • Original sound, Mono • HRTF-30 • Test signal (no delay) • Delayed Sound (7.25 ms) • Final Sound • HRTF-110 • Delayed Sound (7.25 ms) • Final Sound 7.25 ms 14.5 ms 17.4 ms 7.25 ms 14.5 ms 17.4 ms

  12. Conclusion Conclusion • Introducing delay in the frequency band below 1.5 kHz produces reverberant sound • The final sound is better than HRTF sound in sense of the sound diffusion. • Depending on the audio characteristic, the optimum delay time to obtain de-correlated sound (small correlation coefficient) may vary. • When the delay is very high, it simulates big halls.

  13. References • “Improved 3D Sound Using Wavelets”, U. P. Chong, H. Kim, K. N. Kim, IEEE Information Systems and Technologies, 2001. • “HRTF Measurements of a KEMAR Dummy-Head Microphone”, MIT Media Lab Perceptual Computing- Technical Report #280. • “HRTF Measurements of a KEMAR Dummy-Head Microphone”, http://sound.media.mit.edu/KEMAR.html • “Virtually Auditory Space Generation and Applications”, Simon Carlie, Chapman and Hall, 1996.

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