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Approximating the head-related transfer function using simple geometric models of the head and torso
V Ralph Algazi1, Richard O Duda, Ramani Duralswami
1Center for Image Processing and Integrated Computing, University of California, Davis 95616, USA.
The Journal of the Acoustical Society of America
|November 15, 2002
Summary
Simple head and torso models reveal how torso reflections and shadow influence head-related transfer function (HRTF) at low frequencies. These geometric models offer insights into elevation cues for distant sound sources.
Area of Science:
- Acoustics
- Bioacoustics
- Computational Auditory Scene Analysis
Background:
- The head-related transfer function (HRTF) describes how sound is filtered by the head, torso, and outer ear.
- Understanding HRTF, especially for distant sources, is crucial for spatial audio and virtual reality.
- The low-frequency behavior of HRTF is complex and influenced by torso geometry.
Purpose of the Study:
- To develop simple geometric models of the head and torso.
- To investigate the low-frequency HRTF behavior, particularly at low elevations.
- To quantify torso reflections and torso shadow effects on HRTF.
Main Methods:
- Constructed head-and-torso models by combining spherical head models with spherical and ellipsoidal torso models.
- Employed multipole reexpansion and boundary element methods for HRTF computation.
- Validated model HRTFs against acoustic measurements using the KEMAR mannequin.
Main Results:
- Geometric models provide insight into low-frequency HRTF, especially at low elevations.
- Computed HRTFs demonstrate elevation-dependent torso reflections and torso shadow effects.
- Identified a torso bright spot and significant frequency attenuation (above 1 kHz) due to torso shadow.
Conclusions:
- Torso reflections and shadow are significant factors influencing HRTF and providing elevation cues.
- Geometric head-and-torso models offer good approximations of HRTF.
- The computational methods used are valid for HRTF modeling.