@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 {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 {14028,
	title = {Extracting the frequencies of the pinna spectral notches in measured head related impulse responses},
	journal = {The Journal of the Acoustical Society of America},
	volume = {118},
	year = {2005},
	month = {2005///},
	pages = {364 - 374},
	abstract = {The head related impulse response (HRIR) characterizes the auditory cues created by scattering of sound off a person{\textquoteright}s anatomy. The experimentally measured HRIR depends on several factors such as reflections from body parts (torso, shoulder, and knees), head diffraction, and reflection/diffraction effects due to the pinna. Structural models (Algazi et al., 2002; Brown and Duda, 1998) seek to establish direct relationships between the features in the HRIR and the anatomy. While there is evidence that particular features in the HRIR can be explained by anthropometry, the creation of such models from experimental data is hampered by the fact that the extraction of the features in the HRIR is not automatic. One of the prominent features observed in the HRIR, and one that has been shown to be important for elevation perception, are the deep spectral notches attributed to the pinna. In this paper we propose a method to robustly extract the frequencies of the pinna spectral notches from the measured HRIR, distinguishing them from other confounding features. The method also extracts the resonances described by Shaw (1997). The techniques are applied to the publicly available CIPIC HRIR database (Algazi et al., 2001c). The extracted notch frequencies are related to the physical dimensions and shape of the pinna.},
	keywords = {acoustic wave reflection, acoustic wave scattering, anthropometry, Ear, hearing, physiological models},
	doi = {10.1121/1.1923368},
	url = {http://link.aip.org/link/?JAS/118/364/1},
	author = {Raykar,Vikas C. and Duraiswami, Ramani and Yegnanarayana,B.}
}
@conference {14026,
	title = {The manifolds of spatial hearing},
	booktitle = {Acoustics, Speech, and Signal Processing, 2005. Proceedings. (ICASSP {\textquoteright}05). IEEE International Conference on},
	volume = {3},
	year = {2005},
	month = {2005/03//},
	pages = {iii/285 - iii/288 Vol. 3 - iii/285 - iii/288 Vol. 3},
	abstract = {We present exploratory studies on learning the non-linear manifold structure, in head related impulse responses (HRIRs). We use the recently popular locally linear embedding technique. The lower dimensional manifold encodes the perceptual information in the HRIRs, namely the direction of the sound source. Based on this, we propose a new method for HRIR interpolation. We also propose that the distance between two HRIRs of an individual be taken as the geodesic distance on the learned manifold.},
	keywords = {acoustics;, dimensional, direction, distance;, EMBEDDING, encoding;, geodesic, Head, hearing, hearing;, HRIR, impulse, information, interpolation;, learned, linear, localization;, locally, low, manifold, manifold;, manifolds;, nonlinear, perceptual, related, response;, responses;, sound, source, spatial, structure;, technique;, transient},
	doi = {10.1109/ICASSP.2005.1415702},
	author = {Duraiswami, Ramani and Raykar,V.C.}
}
