AES Budapest 2012
Paper Session P19
P19 - Spatial Audio: Part 2
Saturday, April 28, 14:30 — 17:30 (Room: Lehar)
P19-1 Sound Field Reproduction Method in Spatio-Temporal Frequency Domain Considering Directivity of Loudspeakers—Shoichi Koyama, Ken'ichi Furuya, Yusuke Hiwasaki, Yoichi Haneda, NTT Cyber Space Laboratories, NTT Corporation - Musashino-shi, Tokyo, Japan
A method for transforming received signals of a microphone array into driving signals of a loudspeaker array for sound field reproduction is needed to achieve real-time sound field transmission systems from the far-end to the near-end. We recently proposed a transform method using planar or linear microphone and loudspeaker arrays in the spatio-temporal frequency domain, which is more efficient than conventional methods based on a least squares algorithm. In this method, the directivity of loudspeakers in the array is assumed to be omnidirectional to derive the transform filter. However the directivity of common loudspeakers is not always omnidirectional, especially at high frequencies. We therefore propose a transform method that takes into consideration the directivity of loudspeakers in the array, which is derived using analytical and numerical approaches. Numerical simulation results indicated that the accurately reproduced region of the proposed method was larger than that of the method with an omnidirectional assumption.
Convention Paper 8664 (Purchase now)
P19-2 Practical Applications of Chameleon Subwoofer Arrays—Adam J. Hill, Malcolm O. J. Hawksford, University of Essex - Colchester, Essex, UK
Spatiotemporal variations of the low-frequency response in a closed-space are predominantly caused by room-modes. Chameleon subwoofer arrays (CSA) were developed to minimize this variance over a listening area using multiple independently-controllable source components and calibrated with one-time measurements. Although CSAs are ideally implemented using hybrid (multiple source component) subwoofers, they can alternatively be realized using conventional subwoofers. This capability is exploited in this work where various CSA configurations are tested using commercially-available subwoofers in a small-sized listening room. Spectral and temporal evaluation is performed using tone-burst and maximum length sequence (MLS) measurements. The systems are implemented with practicality in mind, keeping the number of subwoofers and calibration measurements to a minimum while maintaining correction benefits.
Convention Paper 8665 (Purchase now)
P19-3 Localization in Binaural Reproduction with Insert Headphones—Marko Hiipakka, Marko Takanen, Symeon Delikaris-Manias, Archontis Politis, Ville Pulkki, Aalto University - Espoo, Finland
Circumaural headphones are commonly used in binaural reproduction and it is well known that individual equalization of the headphones improves the quality of the reproduction. The suitability of insert headphones to binaural reproduction has not been studied partly due the lack of a commonly accepted individual equalization method for insert headphones. Recently, a method to estimate the frequency response evoked by insert headphones has been presented. In this paper the localization accuracy of test subjects is evaluated in binaural listening with insert headphones and high-quality circumaural headphones. The results show that the accuracy with inserts is similar to that with circumaural headphones when the recently proposed method is applied for equalization, which motivates their use in binaural reproduction.
Convention Paper 8666 (Purchase now)
P19-4 A Comparative Evaluation between Numerical Techniques for Implementing the Acoustic Diffusion Equation Model—Juan M. Navarro, Juan E. Noriega, San Antonio's Catholic University of Murcia - Guadalupe, Spain; Jose Escolano, University of Jaén - Linares, Spain; Jose J. Lopez, Universidad Politécnica de Valencia - Valencia, Spain
The acoustic diffusion equation model is an energy-based model that is being successfully applied in room acoustics for predicting the late part of the decay, in the past few years. Early researches usually used a finite element method to solve the diffusion equation model. Recently, an alternative implementation, using finite difference methods has been proposed. A comparison between both numerical techniques could be helpful to clarify the pros and cons of each method. In this paper this evaluation is made by several simulations in a cubic shaped room. Both prediction accuracy and computational performance are compared using different absorption distributions. It is suggested that the finite difference implementation is less computationally intensive than the finite element method. Moreover, the obtained values in the simulations are accurate, at least as well as other geometrical models.
Convention Paper 8667 (Purchase now)
P19-5 A Bayesian Framework for Sound Source Localization—José Escolano, University of Jaén - Linares, Spain; Maximo Cobos, University of Valencia - Burjassot, Valencia, Spain; Jose M. Pérez-Lorenzo, University of Jaén - Linares, Spain; José J. López, Universidad Politécnica de Valencia - Valencia, Spain; Ning Xiang, Rensselaer Polytechnic Institute - Troy, NY, USA
The localization of sound sources, and particularly speech, has a numerous number of applications to the industry. This has motivated a continuous effort in developing robust direction-of-arrival detection algorithms. Time difference of arrival-based methods, and particularly, generalized cross-correlation approaches have been widely investigated in acoustic signal processing. Once a probability function distribution is obtained, indicating those directions of arrival with highest probability, the vast majority of methods have to assume a certain number of sound sources in order to process the information conveniently. In this paper a model selection based on a Bayesian framework is proposed in order to determine, in an unsupervised way, how many sound sources are estimated. Real measurements using two microphones are used to corroborate the proposed model.
Convention Paper 8668 (Purchase now)
P19-6 A Comparison of Modal versus Delay-and-Sum Beamforming in the Context of Data-Based Binaural Synthesis—Sascha Spors, Hagen Wierstorf, Matthias Geier, Deutsche Telekom Laboratories, Technische Universität Berlin - Berlin, Germany
Several approaches to data-based binaural synthesis have been published that capture a sound field by means of a spherical microphone array. The captured sound field is decomposed into plane waves that are then auralized using head-related transfer functions (HRTFs). The decomposition into plane waves is often based upon modal beamforming techniques that represent the captured sound field with respect to surface spherical harmonics. An efficient and numerically stable approximation to modal beamforming is the delay-and-sum technique. This paper compares these two beamforming techniques in the context of data-based binaural synthesis. Their frequency- and time-domain properties are investigated, as well as the perceptual properties of the resulting binaural synthesis according to a binaural model.
Convention Paper 8669 (Purchase now)
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