implementation of 3d audio using interpolated head-related...
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Implementation of 3D Audio using
Interpolated Head-Related Transfer Functions
Mike HeilemannKedar Shashidhar
Alex Venuti
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HRIR: Head-Related Impulse ResponseHRTF: Head-Related Transfer FunctionCIPIC: Center for Image Processing and
Integrated Computing (University ofCalifornia Davis)
Azimuth: horizontal angle (from directly ahead)
Elevation: vertical angle (from directly ahead)
Terms / Acronyms
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● Understand existing HRTF code for Matlab
● Choose method for interpolating impulse responses
● Modify existing Matlab code using interpolation algorithms in attempt to reduce number of stored impulse responses necessary to recreate 3D soundfield
● Investigate real-time applications of 3D audio
Goals
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CIPIC HRTF Database
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CIPIC HRTF Database
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● Won’t have to physically measure impulse response at as many points
● Reduce size of HRIR array to maximize memory efficiency
● Allows for smoother transition between points
Advantages of Interpolation
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Vector-Based Amplitude Panning:
G. de Sousa & M. Queiroz, “Two Approaches for HRTF interpolation”
Interpolation Method
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● getNearest3.m○ in - elevation, azimuth, HRIR struct○ out - three nearest points in sound field and
corresponding impulse responses
● SweepTest.m○ user declares two azimuth and elevation values○ will sweep audio in a straight line between two
points using three point interpolation
Description of Matlab Functions
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● Original HRIR Points○ Azimuths - 25○ Elevations - 50○ Total Pts - 1250
● Points Needed with Interpolation○ Azimuths - 7○ Elevations - 13○ Total Pts - 91
Reduction of Data Points
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The following figures use this example point:
Azimuth = 20 degreesElevation = 28.125 degrees
Time/Frequency Response Comparison
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Files are in C:\HRTF examples○ example_act○ example_int○ example_int_corrected○ orbit1_all○ orbit1_reduced○ orbit2_all○ orbit2_reduced
Audio Comparison
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Real-Time Aspects
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● HRTFs are different for each person
● More sensitive to Left/Right changes than
Up/Down or Forward/Back
■ Evolutionary Hearing
● All points were at same radius
● Time lag between interpolated pts.
Problems With HRTF Interpolation Method
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Video Games● Who wouldn’t want to be able to close eyes and
feel like they are actually in the game?
Room Acoustic Evaluation● Allows you to examine acoustic properties of a
room under different sound sources and room conditions
Hearing Aids● Frequency-dependent hearing loss compensation.
Practical Applications
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Algazi, V. R., Duda, R. O., Thompson, D. M., & Avendano, C. (2001). The CIPIC HRTF database. In Applications of Signal Processing to Audio and Acoustics, 2001 IEEE Workshop on the Applications of Signal Processing to Audio and Electroacoustics (pp. 99-102). IEEE.
CIPIC Database - Copyright (c) 2001 The Regents of the University of California. All Rights Reserved
Doukhan, D., & Sédès, A. C. (2009). A Binaural Synthesis External for Pure Data. In PD Convention.
de Sousa, G. H., & Queiroz, M. (2009, September). Two approaches for HRTF interpolation. In The 12th Brazilian Symposium on Computer Music (SBCM 2009).
References
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Questions???