Algazi V Ralph, Duda Richard O, Duralswami Ramani, Gumerov Nail A, Tang Zhihui
Center for Image Processing and Integrated Computing, University of California, Davis 95616, USA.
J Acoust Soc Am. 2002 Nov;112(5 Pt 1):2053-64. doi: 10.1121/1.1508780.
The head-related transfer function (HRTF) for distant sources is a complicated function of azimuth, elevation and frequency. This paper presents simple geometric models of the head and torso that provide insight into its low-frequency behavior, especially at low elevations. The head-and-torso models are obtained by adding both spherical and ellipsoidal models of the torso to a classical spherical-head model. Two different numerical techniques--multipole reexpansion and boundary element methods--are used to compute the HRTF of the models in both the frequency domain and the time domain. These computed HRTFs quantify the characteristics of elevation-dependent torso reflections for sources above the torso-shadow cone, and reveal the qualitatively different effects of torso shadow for sources within the torso-shadow cone. These effects include a torso bright spot that is prominent for the spherical torso, and significant attenuation of frequencies above 1 kHz in a range of elevations. Both torso reflections and torso shadow provide potentially significant elevation cues. Comparisons of the model HRTF with acoustic measurements in the horizontal, median, and frontal planes confirm the basic validity of the computational methods and establish that the geometric models provide good approximations of the HRTF for the KEMAR mannequin with its pinnae removed.
远场声源的头部相关传递函数（HRTF）是方位角、仰角和频率的复杂函数。本文提出了头部和躯干的简单几何模型，以深入了解其低频特性，尤其是在低仰角时的特性。头部和躯干模型是通过将躯干的球形和椭球形模型添加到经典的球形头部模型中获得的。两种不同的数值技术——多极重新展开法和边界元法——被用于在频域和时域中计算模型的HRTF。这些计算得到的HRTF量化了躯干阴影锥上方声源的仰角相关躯干反射特性，并揭示了躯干阴影锥内声源的定性不同影响。这些影响包括球形躯干中突出的躯干亮点，以及在一定仰角范围内高于1kHz频率的显著衰减。躯干反射和躯干阴影都提供了潜在的重要仰角线索。将模型HRTF与水平、正中矢状和额平面的声学测量结果进行比较，证实了计算方法的基本有效性，并确定几何模型能够很好地近似去除耳廓的KEMAR人体模型的HRTF。
