@article {13957,
	title = {Insights into head-related transfer function: Spatial dimensionality and continuous representation},
	journal = {The Journal of the Acoustical Society of America},
	volume = {127},
	year = {2010},
	month = {2010///},
	pages = {2347 - 2357},
	abstract = {This paper studies head-related transfer function (HRTF) sampling and synthesis in a three-dimensional auditory scene based on a general modal decomposition of the HRTF in all frequency-range-angle domains. The main finding is that the HRTF decomposition with the derived spatial basis function modes can be well approximated by a finite number, which is defined as the spatial dimensionality of the HRTF. The dimensionality determines the minimum number of parameters to represent the HRTF corresponding to all directions and also the required spatial resolution in HRTF measurement. The general model is further developed to a continuous HRTF representation, in which the normalized spatial modes can achieve HRTF near-field and far-field representations in one formulation. The remaining HRTF spectral components are compactly represented using a Fourier spherical Bessel series, where the aim is to generate the HRTF with much higher spectral resolution in fewer parameters from typical measurements, which usually have limited spectral resolution constrained by sampling conditions. A low-computation algorithm is developed to obtain the model coefficients from the existing measurements. The HRTF synthesis using the proposed model is validated by three sets of data: (i) synthetic HRTFs from the spherical head model, (ii) the MIT KEMAR (Knowles Electronics Mannequin for Acoustics Research) data, and (iii) 45-subject CIPIC HRTF measurements.},
	keywords = {acoustic signal processing, Bessel functions, Fourier series, hearing, Transfer functions},
	doi = {10.1121/1.3336399},
	url = {http://link.aip.org/link/?JAS/127/2347/1},
	author = {Zhang,Wen and Abhayapala,Thushara D. and Kennedy,Rodney A. and Duraiswami, Ramani}
}
@conference {18467,
	title = {Regularized HRTF fitting using spherical harmonics},
	booktitle = {IEEE Workshop on Applications of Signal Processing to Audio and Acoustics, 2009. WASPAA {\textquoteright}09},
	year = {2009},
	month = {2009/10//},
	pages = {257 - 260},
	publisher = {IEEE},
	organization = {IEEE},
	abstract = {By the Helmholtz reciprocity principle, the head-related transfer function (HRTF) is equivalent to an acoustic field created by a transmitter placed at the ear location. Therefore, it can be represented as a spherical harmonics spectrum - a weighted sum of spherical harmonics. Such representations are useful in theoretical and computational analysis. Many different (often severely undersampled) grids are used for HRTF measurement, making the spectral reconstruction difficult. In this paper, two methods of obtaining the spectrum are presented and analyzed both on synthetic (ground-truth data available) and real HRTF measurements.},
	keywords = {Acoustic applications, acoustic field, Acoustic fields, acoustic intensity measurement, Acoustic measurements, acoustic signal processing, Acoustic testing, acoustic waves, array signal processing, audio acoustics, circular arrays, computational analysis, Ear, ear location, head-related transfer function, Helmholtz reciprocity principle, HRTF, HRTF fitting, Loudspeakers, Microphones, Position measurement, signal reconstruction, spatial audio, spectral reconstruction, spherical harmonics, Transfer functions},
	isbn = {978-1-4244-3678-1},
	doi = {10.1109/ASPAA.2009.5346521},
	author = {Zotkin,Dmitry N and Duraiswami, Ramani and Gumerov, Nail A.}
}
@conference {14516,
	title = {Efficient Conversion of X.Y Surround Sound Content to Binaural Head-Tracked Form for HRTF-Enabled Playback},
	booktitle = {IEEE International Conference on Acoustics, Speech and Signal Processing, 2007. ICASSP 2007},
	volume = {1},
	year = {2007},
	month = {2007/04//},
	pages = {I-21-I-24 - I-21-I-24},
	publisher = {IEEE},
	organization = {IEEE},
	abstract = {Binaural presentation of X.Y sound is usually performed using virtual audio principles - that is, by attempting to virtually reproduce the setup of the X+Y loudspeakers in the reference room configuration. The computational cost of such playback is linear in the number of channels in the X.Y setup. We present a novel scheme that computes, offline, a spatio-temporal representation of the sound field in the listening area and store it as a multipole expansion. During head-tracked playback, the binaural signal is obtained by evaluating the multipole expansion at the ear position corresponding to the current user pose, resulting in a fixed playback cost. The representation is further extended to incorporate individualized HRTFs at no additional cost. Simulation results are presented.},
	keywords = {Acoustic fields, Acoustic scattering, acoustic signal processing, audio acoustics, Audio systems, binaural head-tracked, binaural presentation, Computational efficiency, Costs, Ear, head-related transfer function, Headphones, HRTF-enabled playback, Loudspeakers, Music, reverberation, sound field, spatio-temporal representation, surround sound, surround sound content, Transfer functions, virtual audio principles},
	isbn = {1-4244-0727-3},
	doi = {10.1109/ICASSP.2007.366606},
	author = {Zotkin,Dmitry N and Duraiswami, Ramani and Gumerov, Nail A.}
}
@conference {18458,
	title = {Fast Multipole Accelerated Boundary Elements for Numerical Computation of the Head Related Transfer Function},
	booktitle = {IEEE International Conference on Acoustics, Speech and Signal Processing, 2007. ICASSP 2007},
	volume = {1},
	year = {2007},
	month = {2007/04//},
	pages = {I-165-I-168 - I-165-I-168},
	publisher = {IEEE},
	organization = {IEEE},
	abstract = {The numerical computation of head related transfer functions has been attempted by a number of researchers. However, the cost of the computations has meant that usually only low frequencies can be computed and further the computations take inordinately long times. Because of this, comparisons of the computations with measurements are also difficult. We present a fast multipole based iterative preconditioned Krylov solution of a boundary element formulation of the problem and use a new formulation that enables the reciprocity technique to be accurately employed. This allows the calculation to proceed for higher frequencies and larger discretizations. Preliminary results of the computations and of comparisons with measured HRTFs are presented.},
	keywords = {Acceleration, Acoustic measurements, Acoustic scattering, audio signal processing, boundary element formulation, Boundary element method, Boundary element methods, boundary-elements methods, Costs, Ear, Fast Multipole Method, Frequency, Head related transfer function, HUMANS, Irrigation, iterative methods, multipole accelerated boundary elements, multipole based iterative preconditioned Krylov solution, numerical computation, Reciprocity, Transfer functions},
	isbn = {1-4244-0727-3},
	doi = {10.1109/ICASSP.2007.366642},
	author = {Gumerov, Nail A. and Duraiswami, Ramani and Zotkin,Dmitry N}
}
@article {14009,
	title = {Fast head-related transfer function measurement via reciprocity},
	journal = {The Journal of the Acoustical Society of America},
	volume = {120},
	year = {2006},
	month = {2006///},
	pages = {2202 - 2215},
	abstract = {An efficient method for head-related transfer function (HRTF) measurement is presented. By applying the acoustical principle of reciprocity, one can swap the speaker and the microphone positions in the traditional (direct) HRTF measurement setup, that is, insert a microspeaker into the subject{\textquoteright}s ear and position several microphones around the subject, enabling simultaneous HRTF acquisition at all microphone positions. The setup used for reciprocal HRTF measurement is described, and the obtained HRTFs are compared with the analytical solution for a sound-hard sphere and with KEMAR manikin HRTF obtained by the direct method. The reciprocally measured sphere HRTF agrees well with the analytical solution. The reciprocally measured and the directly measured KEMAR HRTFs are not exactly identical but agree well in spectrum shape and feature positions. To evaluate if the observed differences are significant, an auditory localization model based on work byJ. C. Middlebrooks [J. Acoust. Soc. Am. 92, 2607{\textendash}2624 (1992)
] was used to predict where a virtual sound source synthesized with the reciprocally measured HRTF would be localized if the directly measured HRTF were used for the localization. It was found that the predicted localization direction generally lies close to the measurement direction, indicating that the HRTFs obtained via the two methods are in good agreement.
},
	keywords = {hearing, Microphones, Transfer functions},
	doi = {10.1121/1.2207578},
	url = {http://link.aip.org/link/?JAS/120/2202/1},
	author = {Zotkin,Dmitry N and Duraiswami, Ramani and Grassi,Elena and Gumerov, Nail A.}
}
@article {18459,
	title = {Rendering localized spatial audio in a virtual auditory space},
	journal = {IEEE Transactions on Multimedia},
	volume = {6},
	year = {2004},
	month = {2004/08//},
	pages = {553 - 564},
	abstract = {High-quality virtual audio scene rendering is required for emerging virtual and augmented reality applications, perceptual user interfaces, and sonification of data. We describe algorithms for creation of virtual auditory spaces by rendering cues that arise from anatomical scattering, environmental scattering, and dynamical effects. We use a novel way of personalizing the head related transfer functions (HRTFs) from a database, based on anatomical measurements. Details of algorithms for HRTF interpolation, room impulse response creation, HRTF selection from a database, and audio scene presentation are presented. Our system runs in real time on an office PC without specialized DSP hardware.},
	keywords = {-D audio processing, 3-D audio processing, Audio databases, audio signal processing, audio user interfaces, augmented reality, data sonification, Digital signal processing, head related transfer functions, head-related transfer function, Interpolation, Layout, perceptual user interfaces, Real time systems, Rendering (computer graphics), Scattering, spatial audio, Transfer functions, User interfaces, virtual audio scene rendering, virtual auditory spaces, virtual environments, Virtual reality, virtual reality environments},
	isbn = {1520-9210},
	doi = {10.1109/TMM.2004.827516},
	author = {Zotkin,Dmitry N and Duraiswami, Ramani and Davis, Larry S.}
}
@conference {18470,
	title = {Virtual audio system customization using visual matching of ear parameters},
	booktitle = {16th International Conference on Pattern Recognition, 2002. Proceedings},
	volume = {3},
	year = {2002},
	month = {2002///},
	pages = {1003- 1006 vol.3 - 1003- 1006 vol.3},
	publisher = {IEEE},
	organization = {IEEE},
	abstract = {Applications in the creation of virtual auditory spaces (VAS) and sonification require individualized head related transfer functions (HRTFs) for perceptual fidelity. HRTFs exhibit significant variation from person to person due to differences between their pinnae, and their body sizes. We propose and preliminarily implement a simple HRTF customization based on the use of a published database of HRTFs (Algazi et al., 2001) that also contains geometrical measurements of subject pinnae. We measure some of these features via simple image processing, and select the HRTF that has features most closely corresponding to the individual{\textquoteright}s features. This selection procedure is implemented along with the virtual auditory system described in (Zotkin et al., 2002), and listener tests conducted comparing the customized HRTF and a fixed HRTF. Despite the simplicity of the method, tests reveal average improvement in localization accuracy of about 25 percent, though performance improvement varies with source location and individuals.},
	keywords = {acoustic signal processing, Audio systems, Auditory system, Computer vision, database, Ear, ear parameter matching, geometrical measurements, Head, head related transfer functions, HRTF customization, Image databases, IMAGE PROCESSING, medical image processing, performance improvement, Position measurement, sonification, Spatial databases, System testing, Transfer functions, virtual audio system customization, virtual auditory spaces, virtual auditory system, visual matching},
	isbn = {0-7695-1695-X},
	doi = {10.1109/ICPR.2002.1048207},
	author = {Zotkin,Dmitry N and Duraiswami, Ramani and Davis, Larry S. and Mohan,A. and Raykar,V.}
}
@conference {14529,
	title = {Modeling the effect of a nearby boundary on the HRTF},
	booktitle = {2001 IEEE International Conference on Acoustics, Speech, and Signal Processing, 2001. Proceedings. (ICASSP {\textquoteright}01)},
	volume = {5},
	year = {2001},
	month = {2001///},
	pages = {3337-3340 vol.5 - 3337-3340 vol.5},
	publisher = {IEEE},
	organization = {IEEE},
	abstract = {Understanding and simplified modeling of the head related transfer function (HRTF) holds the key to many applications in spatial audio. We develop an analytical solution to the problem of scattering of sound from a sphere in the vicinity of an infinite plane. Using this solution we study the influence of a nearby scattering rigid surface, on a spherical model for the HRTF},
	keywords = {Acoustic scattering, acoustic signal processing, acoustic wave reflection, acoustic wave scattering, architectural acoustics, audio signal processing, Biological system modeling, boundary effect modeling, Computer interfaces, Ear, Educational institutions, Frequency, Head related transfer function, HRTF, HUMANS, infinite plane, Laboratories, Nails, Raman scattering, rigid surface, room environment, sound pressure level, sound scattering, spatial audio, sphere, spherical model, Transfer functions, wall influence},
	isbn = {0-7803-7041-4},
	doi = {10.1109/ICASSP.2001.940373},
	author = {Gumerov, Nail A. and Duraiswami, Ramani}
}
