@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}
}
@article {18457,
	title = {Plane-Wave Decomposition of Acoustical Scenes Via Spherical and Cylindrical Microphone Arrays},
	journal = {IEEE Transactions on Audio, Speech, and Language Processing},
	volume = {18},
	year = {2010},
	month = {2010/01//},
	pages = {2 - 16},
	abstract = {Spherical and cylindrical microphone arrays offer a number of attractive properties such as direction-independent acoustic behavior and ability to reconstruct the sound field in the vicinity of the array. Beamforming and scene analysis for such arrays is typically done using sound field representation in terms of orthogonal basis functions (spherical/cylindrical harmonics). In this paper, an alternative sound field representation in terms of plane waves is described, and a method for estimating it directly from measurements at microphones is proposed. It is shown that representing a field as a collection of plane waves arriving from various directions simplifies source localization, beamforming, and spatial audio playback. A comparison of the new method with the well-known spherical harmonics based beamforming algorithm is done, and it is shown that both algorithms can be expressed in the same framework but with weights computed differently. It is also shown that the proposed method can be extended to cylindrical arrays. A number of features important for the design and operation of spherical microphone arrays in real applications are revealed. Results indicate that it is possible to reconstruct the sound scene up to order p with p2 microphones spherical array.},
	keywords = {Acoustic fields, acoustic position measurement, acoustic signal processing, acoustic waves, acoustical scene analysis, array signal processing, circular arrays, cylindrical microphone arrays, direction-independent acoustic behavior, microphone arrays, orthogonal basis functions, plane-wave decomposition, Position measurement, signal reconstruction, sound field reconstruction, sound field representation, source localization, spatial audio playback, spherical harmonics based beamforming algorithm, spherical microphone arrays},
	isbn = {1558-7916},
	doi = {10.1109/TASL.2009.2022000},
	author = {Zotkin,Dmitry N and Duraiswami, Ramani and Gumerov, Nail A.}
}
@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 {18477,
	title = {Imaging concert hall acoustics using visual and audio cameras},
	booktitle = {IEEE International Conference on Acoustics, Speech and Signal Processing, 2008. ICASSP 2008},
	year = {2008},
	month = {2008///},
	pages = {5284 - 5287},
	publisher = {IEEE},
	organization = {IEEE},
	abstract = {Using a developed real time audio camera, that uses the output of a spherical microphone array beamformer steered in all directions to create central projection to create acoustic intensity images, we present a technique to measure the acoustics of rooms and halls. A panoramic mosaiced visual image of the space is also create. Since both the visual and the audio camera images are central projection, registration of the acquired audio and video images can be performed using standard computer vision techniques. We describe the technique, and apply it to the examine the relation between acoustical features and architectural details of the Dekelbaum concert hall at the Clarice Smith Performing Arts Center in College Park, MD.},
	keywords = {Acoustic imaging, acoustic intensity images, acoustic measurement, Acoustic measurements, Acoustic scattering, acoustic signal processing, acoustical camera, acoustical scene analysis, acquired audio registration, audio cameras, audio signal processing, CAMERAS, central projection, Computer vision, Educational institutions, HUMANS, image registration, Image segmentation, imaging concert hall acoustics, Layout, microphone arrays, panoramic mosaiced visual image, Raman scattering, reverberation, room acoustics, spherical microphone array beamformer, spherical microphone arrays, video image registration, visual cameras},
	isbn = {978-1-4244-1483-3},
	doi = {10.1109/ICASSP.2008.4518852},
	author = {O{\textquoteright}Donovan,A. and Duraiswami, Ramani and Zotkin,Dmitry N}
}
@conference {18483,
	title = {Sound field decomposition using spherical microphone arrays},
	booktitle = {IEEE International Conference on Acoustics, Speech and Signal Processing, 2008. ICASSP 2008},
	year = {2008},
	month = {2008///},
	pages = {277 - 280},
	publisher = {IEEE},
	organization = {IEEE},
	abstract = {Spherical microphone arrays offer a number of attractive properties such as direction-independent acoustic behavior and ability to reconstruct the sound field in the vicinity of the array. Such ability is necessary in applications such as ambisonics and recreating auditory environment over headphones. We compare the performance of two scene reconstruction algorithms - one based on least-squares fitting the observed potentials and another based on computing the far-field signature function directly from the microphone measurements. A number of features important for the design and operation of spherical microphone arrays in real applications are revealed. Results indicate that it is possible to reconstruct the sound scene up to order p with p2 microphones.},
	keywords = {Acoustic applications, Acoustic arrays, Acoustic fields, acoustic position measurement, Acoustic propagation, acoustic signal processing, acoustic waves, array signal processing, Equations, far-field signature function, Layout, least-squares fitting, microphone arrays, scene reconstruction algorithms, Signal processing algorithms, sound field decomposition, spherical microphone arrays, Surface acoustic waves},
	isbn = {978-1-4244-1483-3},
	doi = {10.1109/ICASSP.2008.4517600},
	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 {18480,
	title = {Frequency Independent Flexible Spherical Beamforming Via Rbf Fitting},
	booktitle = {2006 IEEE International Conference on Acoustics, Speech and Signal Processing, 2006. ICASSP 2006 Proceedings},
	volume = {5},
	year = {2006},
	month = {2006/05//},
	pages = {V-V - V-V},
	publisher = {IEEE},
	organization = {IEEE},
	abstract = {We describe a new method for sound analysis using a spherical microphone array without the use of quadrature over the sphere. Quadrature based solutions are very sensitive to the placement of microphones on the sphere, needing measurements to be made at exactly the quadrature positions. We propose to use fitting with band-limited radial basis functions (RBFs) rather than quadrature. Our approach results in frequency independent beamformer weights for flexibly placed microphone locations. Results are demonstrated using both synthetic and real spherical array data},
	keywords = {acoustic signal processing, array signal processing, band-limited radial basis functions, Computer science, Educational institutions, Eigenvalues and eigenfunctions, Equations, Frequency, frequency independent beamformer weights, frequency independent flexible spherical beamforming, microphone arrays, Nails, Position measurement, RBF fitting, Robustness, sound analysis, spherical array data, spherical microphone array},
	isbn = {1-4244-0469-X},
	doi = {10.1109/ICASSP.2006.1661208},
	author = {Yerukhimovich,A. and Duraiswami, Ramani and Gumerov, Nail A. and Zotkin,Dmitry N}
}
@conference {14522,
	title = {Plane-wave decomposition analysis for spherical microphone arrays},
	booktitle = {IEEE Workshop on Applications of Signal Processing to Audio and Acoustics, 2005},
	year = {2005},
	month = {2005/10//},
	pages = {150 - 153},
	publisher = {IEEE},
	organization = {IEEE},
	abstract = {Spherical microphone arrays have attracted attention for analyzing the sound field in a region and beamforming. The analysis of the recorded sound has been performed in terms of spherical wave-functions, and recently the use of plane-wave expansions has been suggested. We show that the plane-wave basis is intimately related to the spherical wave-functions. Reproduction in terms of both representations satisfies certain band-limit criteria. We provide an error bound that shows that to reproduce the spatial characteristics of a sound of a certain frequency we need to be able to accurately represent sounds of up to a particular order, which establishes a Nyquist-like criterion. The order of the sound field in turn is related to the number of microphones in the array necessary to achieve accurate quadrature on the sphere. These results are illustrated with simulations.},
	keywords = {Acoustic propagation, Acoustic scattering, acoustic signal processing, acoustic waves, array signal processing, band-limit criteria, beamforming, Educational institutions, Fourier transforms, Frequency, Laboratories, microphone arrays, Nails, Nyquist criterion, Nyquist-like criterion, Partial differential equations, plane-wave decomposition analysis, sound field analysis, spherical microphone arrays, spherical wave-functions},
	isbn = {0-7803-9154-3},
	doi = {10.1109/ASPAA.2005.1540191},
	author = {Duraiswami, Ramani and Zhiyun Li and Zotkin,Dmitry N and Grassi,E. and Gumerov, Nail A.}
}
@article {18462,
	title = {Processing of reverberant speech for time-delay estimation},
	journal = {IEEE Transactions on Speech and Audio Processing},
	volume = {13},
	year = {2005},
	month = {2005/11//},
	pages = {1110 - 1118},
	abstract = {In this paper, we present a method of extracting the time-delay between speech signals collected at two microphone locations. Time-delay estimation from microphone outputs is the first step for many sound localization algorithms, and also for enhancement of speech. For time-delay estimation, speech signals are normally processed using short-time spectral information (either magnitude or phase or both). The spectral features are affected by degradations in speech caused by noise and reverberation. Features corresponding to the excitation source of the speech production mechanism are robust to such degradations. We show that these source features can be extracted reliably from the speech signal. The time-delay estimate can be obtained using the features extracted even from short segments (50-100 ms) of speech from a pair of microphones. The proposed method for time-delay estimation is found to perform better than the generalized cross-correlation (GCC) approach. A method for enhancement of speech is also proposed using the knowledge of the time-delay and the information of the excitation source.},
	keywords = {Acoustic noise, acoustic signal processing, array signal processing, data mining, Degradation, delay estimation, Feature extraction, Hilbert envelope, localization algorithm, microphone arrays, microphone location, Microphones, Phase estimation, reverberation, short-time spectral information, Signal processing, source features, source information excitation, speech enhancement, Speech processing, speech production mechanism, speech signal, time-delay, time-delay estimation},
	isbn = {1063-6676},
	doi = {10.1109/TSA.2005.853005},
	author = {Yegnanarayana,B. and Prasanna,S. R.M and Duraiswami, Ramani and Zotkin,Dmitry N}
}
@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 {18461,
	title = {Efficient evaluation of reverberant sound fields},
	booktitle = {Applications of Signal Processing to Audio and Acoustics, 2001 IEEE Workshop on the},
	year = {2001},
	month = {2001///},
	pages = {203 - 206},
	publisher = {IEEE},
	organization = {IEEE},
	abstract = {An image method due to Allen and Berkley (1979) is often used to simulate the effect of reverberation in rooms. This method is relatively expensive computationally. We present a fast method for conducting such simulations using multipole expansions. For M real and image sources and N evaluation points, while the image method requires O(MN) operations, our method achieves the calculations in O(M + N) operations, resulting in a substantial speedup. Applications of our technique are also expected in simulation of virtual audio},
	keywords = {AB algorithm, acoustic signal processing, architectural acoustics, audio signal processing, Computational modeling, Computer interfaces, Computer simulation, Educational institutions, image method, image sources, Impedance, Laboratories, microphone arrays, multipole expansions, Nails, performance evaluation, reverberant sound fields, reverberation, room reverberation, simulation, Simulations, speedup, virtual audio},
	isbn = {0-7803-7126-7},
	doi = {10.1109/ASPAA.2001.969578},
	author = {Duraiswami, Ramani and Gumerov, Nail A. and Zotkin,Dmitry N and Davis, Larry S.}
}
@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}
}
