Frontiers of Engineering Reports on Leading-Edge Engineering from the 2004 NAE Symposium on Frontiers of Engineering (2005) / Chapter Skim
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Spatial Audio Reproduction: Toward Individualized Binaural Sound--William G. Gardner
Spatial Audio Reproduction: Toward Individualized Binaural Sound--William G. Gardner
Pages 113-122
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From page 113... ...
HEARING People hear with two ears, and the two audio signals received at the eardrums completely define the auditory experience. An amazing feature of the auditory system is that with only two ears sounds can be perceived from all directions, and the listener can even sense the distance and size of sound sources.
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From page 114... ...
A complete description of a subject's head response requires hundreds of HRTF measurements from all directions surrounding the subject. Any sound source can be virtually located by filtering the sound with the HRTFs corresponding to the desired location and presenting the resulting binaural signal to the subject using properly equalized headphones.
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From page 115... ...
Instead, a reference head, often a model that represents a typical listener or HRTFs known to perform adequately for a range of different listeners, is used to encode binaural signals for all listeners. This is called a "non-individualized" system (Wenzel et al., 1993)
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From page 116... ...
. The figure shows the complex, yet systematic, variation in spectrum as a function of source direction.
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From page 117... ...
The study tested the localization performance using individualized HRTFs approximated by weighted sums of the five principal components. When the listener's own HRTFs were used, the results were nearly identical.
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From page 118... ...
However, studies have shown that although simplified geometrical models are accurate at low frequencies, they become increasingly inaccurate at higher frequencies. Because of the importance of high-frequency localization cues for proper externalization, elevation perception, and front/back resolution of sound, simplified geometrical models are not suitable for creating individualized HRTFs.
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From page 119... ...
The goal would be a system that could automatically determine individualized HRTFs based on a few digital images of the subject's head and ears. The challenges will be to develop a head model that can morph to fit any head, to obtain a sufficiently accurate ear shape, and to develop ways to estimate the parameters from images of the subject.
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From page 120... ...
5.1 systems have left, center, and right frontal speakers, left and right surround speakers positioned to the sides of the listener, and a subwoofer to reproduce low frequencies. Because 5.1 systems were designed for cinema sound, the focus is on accurate frontal reproduction so that movie dialogue is spatially aligned with images of the actors speaking.
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From page 121... ...
2000. Psychophysical customization of di rectional transfer functions for virtual sound localization.
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