• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.353-358
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• 2002

Human's vision is mostly confined to the area in the front and we, humans heavily depend on the sense of hearing to gather information in areas out of our sight. Thus, the virtual reality system consisting of the 3D sound effect gives the user a much better sense of reality than the system without the sound effect. Virtual 3D sound technology has mainly been researched with binaural system. The conventional binaural sound systems reproduce the desired sound at two arbitrary points using two channels in 3-D space. Head movement of listener might be change the nominal acoustic transfer function and deteriorate the performance of 3D sound system based on loudspeakers that needs a crosstalk canceller. In this paper, low kinds of sensitivity functions of sphere HRTF are derived to investigate the effect of head movement on HRTF in 3D sound system. Changes of HRTF caused by rotational and translational motion of head are obtained as we calculate the derivatives of HRTF with respect to angle and distance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.28-32
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• 2007

While various methods for sound source localization have been developed, most of them utilize on the time difference of arrival (TDOA) between microphones or the measured head related transfer functions (HRTF). In case of a real robot implementation, the former has a merit of light computation load to estimate the sound direction but can not consider the effect of platform on TDOAs, while the latter can, because characteristics of robot platform are included in HRTF. However, the latter needs large resources for the HRTF database of a specific robot platform. We propose the compensation method which has the light computation load while the effect of platform on TDOA can be taken into account. The proposed method is used with spherical head related transfer function (SHRTF) on the assumption that robot platform, for example a robot head, installed microphones can be modeled to a sphere. We verify that the proposed method decreases the estimation error caused by the robot platform through the simulation and experiment in real environment.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.153-156
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• 1999

이 연구에서는 구조적 HRTF(Head-Related Transfer Function) 모델의 구성 이론에 관하여 기술하였다. 이 모델은 강체 구(rigid sphere)에 대한 음파의 전파와 회절 현상에 대한 이를 식을 근거로 구성하였다. 이 모델은, 구성이 단순하고, 모델 구성에 필요한 계수의 수를 극소화 할 수 있기 때문에 실시간 구현에 적합하다. 그리고, 각개인의 머리전달특성에 따른 개인차를 반영하여 모델을 수정할 수 있는 장점이 있다.

• ETRI Journal
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• v.27 no.2
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• pp.153-165
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• 2005

The main purpose of a spatial audio system is to give a listener the same impression as if he/she were present in a recorded environment. A dummy head microphone is generally used for such purposes. Because of its human-like shape, we can obtain good spatial sound images. However, its shape is a restriction on its public use and it is difficult to convert a 2-channel recording into multi-channel signals for an efficient rendering over a multi-speaker arrangement. In order to solve the problems mentioned above, a spatial audio system is proposed that uses multiple microphones on a rigid sphere. The system has five microphones placed on special points of the rigid sphere, and it generates audio signals for headphone, stereo, stereo dipole, 4-channel, and 5-channel reproduction environments. Subjective localization experiments show that front/back confusion, which is a common limitation of spatial audio systems using the dummy head microphone, can be reduced dramatically in 4-channel and 5-channel reproduction environments and can be reduced slightly in a headphone reproduction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.455-461
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• 2000

A multichannel signal processing algorithm for generating real time virtual sound field was proposed. Evaluation of the system performance was done by an objective function that minimizes the difference between the real and generated signals at each control point. Since impulse responses at the surface of a rigid sphere show characteristics similar to those of real HRTF, a rigid sphere model was adequate to simulate the multichannel sound system. A two-channel system and two four-channel systems were studied with various combinations of source locations and speaker positions. The results show that a two-channel system has its best configuration when the angle spanned by the loudspeakers is less than $60^{\circ}$. In the case of four-channel systems, the overall performance was highly improved with one pair of speakers fixed at an optimal position. Left/right symmetry was a reasonable choice, but the additional front/back symmetry degraded the performance of system.