1. Binaural Sound Localization and Filtering By: Dan Hauer Advisor: Dr. Brian D. Huggins 6 December 2005

2. Project Summary Decoding 3D spatial information from: –Stereo audio material –Binaural audio material Filtering above audio based on spatial information to multiple channels based on azimuth angles

3. Theory Behind Stereo Reproduction Example A: ICC = 1 with varying ILD. Example B: The width of the auditory event increases as the ICC decreases.

4. Current Technology in 3D Audio Dolby surround sound audio Binaural Cue Coding (BCC) Binaural Recordings Other technologies exist: –Quadraphonic –Ambisonic –???

5. Dolby Surround Sound Pros: –Widely used industry standard –Capable of accurate reproduction thanks to accepted speaker locations. Cons: –Requires higher bandwidth and storage space –Encoded information requires proprietary decoding Theory: Multiple independent channels of audio are encoded in a proprietary digital stream to be decoded and send to strategically placed loudspeakers.

6. Binaural Cue Coding (BCC) Pros: –Audio playback is flexible, adapting to any number of speakers and placements –Bandwidth is kept low thanks to reduced number of channels Cons: –Requires specialized decoder –Not stereo compatible –Not widely used Theory: Audio information is encoded with a channel for the summed audio material, and a channel for parametric spatial side information.

7. Binaural Recordings Pros: –Most accurate spatial imaging –Can be played back through common stereo equipment –Stereo compatible Cons: –Must be played back through headphones for proper effect –Audio information must be captured live with little or no ability to add or edit spatial audio Theory: Audio information is captured with a specialized dummy head and played back via standard stereo equipment through headphones.

8. Functional Description Input: Computer file containing two channels of stereo or binaural audio information Output: Computer file containing an arbitrary number of channels corresponding to source azimuth angles System will simulate the brain’s binaural localization abilities to audio presented via headphones. Mode of Operation: System will have one mode of operation in which the input file is opened by Matlab, processed, and the output file is written. User will have the option of selecting an input file and configuring the system operation, including defining the interpreted audio sound field.

9. Applications of System Accurate reproduction of material through a circular speaker array Graphical spatial analysis of audio Spatial filtering of recordings to eliminate unwanted sources

10. Spatial Filtering Example Example: Stereo audio playback through headphones.

11. System Block Diagram

12. System Input / Output Diagram

13. Software Flowchart

14. Preliminary Lab Work Calculation of ICLD versus frequency for artificial signals Investigation of HRTF databases and uses Equipment List PC with Matlab

15. Project Time Table WeekTask 1 Computation of ICLD, ICTD, and ICC 2 3 Database restructuring and lookup system. 4 5 System coding and integration. 6 7 8 Visual test program coding. 9 System testing. 10 Research on real-time implementation and project expansion. 11 12 13 Preparation for presentation.

16. Questions? Comments? “I’m all ears!”