• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.2
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• pp.199-207
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• 2008

A hybrid technique that combines the advantages of binaural reproduction and sound field reproduction technique is proposed. The concept of HRTF-field, which is defined as the set of HRTFs corresponding to the various head dislocations, enables us to realize virtual source imaging over a wide area. Conventional binaural($2{\times}2$) reproduction system is redefined as a MIMO system composed of multiple control sources and multiple head locations, and HRTF variations corresponding to various head movement are quantified. Through the direct control of HRTF-field, reproduction error induced by head dislocation can be minimized in least-square-error sense, and consequential disturbances on the virtual source image can be reduced within a selected area. Simple lateralization examples are investigated, and the reproduction error of the proposed technique is compared to that of higher-order Ambisonics.

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.506-512
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• 2006

시각적인 정보전달이 어려운 상황에서의 대상인식, 혹은 시각장애인의 대상인식에 있어서 소리는 어느 정도의 역할을 할 수 있을까? 이 연구는 소리를 통해 대상의 형태정보를 전달하기 위해 진행되었다. 하나의 음(musical tone)을 음높이와 음색, 지속시간을 조정한 후, 머리전달함수(Head-Related Transfer Function: HRTF)를 이용하여 수평선, 수직선, 대각선, 곡선의 형태로 운동하는 3-D 사운드 형태소로 만들었다. 그리고 이들의 연속적인 조합을 통해 단순한 도형에서부터 복잡한 도형, 이들 2차원상의 도형을 단면으로 하는 3차원상의 도형들까지 그려내는 소리자극을 구성하였다. 성인 대학생을 대상으로 한 실험에서, 이렇게 만들어진 청각이미지(auditory image)를 듣고 표상된 형태를 여러 개의 시각적인 이미지들(visual images) 중에서 선택하는 과제를 실시하였는데, 실험 결과는 평균 78%의 정확율을 보였다. 이는 소리를 이용한 형태정보 전달의 가능성이 있음을 시사하는 것이며, 이러한 시도는 청각 인터페이스의 응용범위를 확장하는데 도움이 될 것이다.

• Journal of Advanced Navigation Technology
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• v.14 no.4
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• pp.571-577
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• 2010

Driving aircraft requires extremely complicated and detailed information processing. Pilots perform their tasks by selecting the information relevant to them. In this processing, spatial information presented simultaneously through crossmodal link is advantageous over the one provided in singular sensory mode. In this paper, probability to apply providing visual spatial information along with auditory information to enemy tracking system in aircraft navigation is empirically investigated. The result shows that auditory spatial information, which is virtually created through HRTF is advantageous to visual spatial information alone in attention processing. The findings suggest auditory spatial information along with visual one can be presented through crossmodal link by utilizing stereophonic sound such as HRTF. which is available in the existing simple stereo system.

• Journal of Broadcast Engineering
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• v.16 no.5
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• pp.846-860
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• 2011

The binaural auditory system of human has ability to differentiate the direction and the distance of the sound sources by using the information which are inter-aural intensity difference(IID), inter-aural time difference(ITD) and/or the spectral shape difference(SSD). These information is generated from the acoustical transfer of a sound source to pinna, the outer ears. We can create a virtual sound system using the information which is called Head related transfer function(HRTF). However the performance of 3D sound is not always satisfactory because of non-individual characteristics of the HRTF. In this paper, we propose the algorithm that uses human's auditory characteristics for accurate perception. To achieve this, excitation energy of HRTF, global masking threshold and loudness are applied to the proposed algorithm. Informal listening test shows that the proposed method improves the sound localization characteristics much better than conventional methods.

• The Journal of the Acoustical Society of Korea
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• v.27 no.4
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• pp.207-214
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• 2008

To create 3D sound, we usually use two methods which are two channels or multichannel sound systems. Because of cost and space problems, we prefer two channel sound system to multi-channel. Using a headphone or two speakers, the most typical method to create 3D sound effects is a technology of head related transfer function (HRTF) which contains the information that sound arrives from a sound source to the ears of the listener. But it causes a problem to localize a sound source around a certain places which is called cone-of-confusion. In this paper, we proposed the new algorithm to reduce the confusion of sound image localization. HRTF grouping and psychoacoustics theory are used to boost the spectral cue with spectrum difference among each directions. Informal listening tests show that the proposed method improves the front-back sound localization characteristics much better than conventional methods.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.637-640
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• 2005

We propose a sound source localization method using the Head-Related-Transfer-Function (HRTF) to be implemented in a given platform. HRTFs contain not only the information regarding proper time delays but also phase and magnitude distortions due to diffraction and scattering by the shading object. Therefore, a set of HRTFs for any given platform provides a substantial amount of information as to the whereabouts of the source. In this study, we introduce new phase criterion in order to find the sound source location in accordance with the HRTF database empirically obtained in an anechoic chamber with the given platform. Using this criterion, we analyze the estimation performance of the proposed method in a household environment.

• Journal of the Institute of Convergence Signal Processing
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• v.4 no.4
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• pp.23-29
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• 2003

In this paper, we propose an idea for the improved 3-D sound system using conventional stereo headphones to obtain a better sound diffusion from the mono-sound recorded at an anechoic chamber. We use the HRTF(Head Related Transfer Function) for the sound localization and the wavelet filter bank with time delay for the sound diffusion. And we test the modified HRTF with the various sampling rate. We investigate the effects of the 3-D sound depending on the length of time delay at lowest frequency band. Also the correlation coefficient of the signals between the left channel and the right channel is measured to identify the sound diffusion. At last we obtain the diffusion sound using Cool Edit for reverberation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.541-546
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• 1999

The head-related transfer function (HRTF), which expresses the acoustic process from the sound source to the human ears in the free field, contains critical informations which the location of the source can be traced. It also makes it possible to realize multi-dimensional acoustic system that can approximately generate non-existing sound source. The use of non-individual, common HRTF brings performance degradation in localization ability such as front-back judgment error, elevation judgment error. In this paper, we have reduced the error on vertical plane by increasing the spectral notch level. The performance of the proposed method was Proved through subjective test that it is Possible to improve the ability to locate stationary/moving source.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1035-1044
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• 2010

Head-related transfer function (HRTF) is an acoustic transfer function from a sound source to the ear canal entrance position. HRTFs are very important information in the construction of virtual sound fields. HRTFs also vary for different individuals. In this study, characteristics of HRTF for an average Korean are investigated numerically by comparing with the HRTF for a standard Knowles Electronics Manikin for Acoustic Research (KEMAR). A boundary element (BE) model for an adult Korean is developed using the computerized tomography (CT) data in order to investigate the variation in HRTFs for different individuals. The boundary conditions of the BE model are identified by comparing the numerical results with the experimental results. The numerical model shows that accurate HRTFs can be calculated efficiently over full audible frequency range for individuals.

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.632-637
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• 2006

본 논문에서는 가상현실 환경에서 방위각, 고도, 거리 등의 위치 정보를 인지할 수 있는 3 차원 사운드를 생성하기 위한 구조적 머리전달함수(Head-Related Transfer Function, HRTF) 모델을 제안하고 이를 구현한다. 이를 위해 우선 기존에 연구된 방위각과 고도에 관한 head model 과 pinna model 을 근간으로 거리의 변화를 고려하도록 하는 HRTF 모델을 제안한다. 제안된 거리 변화에 따른 HRTF 모델은 거리 차이에 따른 음압의 변화 모델과 근거리에서 사람의 머리에 의해 생기는 shadowing 모델로 구성된다. 본 논문에서는 제안한 모델로 부터 mono 사운드를 방위각, 고도, 거리를 인지할 수 있는 stereo 사운드로 변환하여 생성하는 3 차원 사운드 생성기를 구현하였고, 일반인을 대상으로 거리에 대한 청취 실험을 통하여 제안한 모델의 성능을 측정하였다. 그리고 제안된 모델을 가상현실의 실감모델인 MP3 에 구현하여 그 효과를 입증하였다.