• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.6
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• pp.1201-1206
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• 2009

According to a lot of investigations, distance perception is influenced by many important cues such as sound pressure level, reflections from the room surface, binaural difference (ITD and ILD), a kind of sound source, and head related transfer functions (HRTF). Two psychoacoustical experiments on auditory distance perception were conducted to examine the effectiveness of the sound pressure level loudness as one of the physical cues in the auditory distance perception under a constant loudspeaker's output level and a constant sound level at the subject's position in the absence of reflections in an anechoic room. Our experimental results showed that the perceived distance of sound image is closer than actual sound source distance with the constant loudspeaker's output level and the constant sound level. Futhermore, the perceived distance of a sound image with constant sound level increased when the actual distance increases up to approximately 2 m while the perceived distance saturated when the sound source distance exceed 2 m. On the other hand, when the condition of loudspeaker's output level was kept constantly, the perceived distance of sound image increased up to around 3m, longer than the conditions of constant sound level at the subject's position. We found that the change in the loudness as a function of distance plays an important role in the auditory distance perception in the absence of reflections..

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.807-810
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• 2000

입체음향 시스템에서 모노음에 방향감을 제어하기 위한 방법으로 FIR 필터 형태의 머리전달함수( HRTF : Head-Related Transfer Function)를 사용한다. 그러나 이때 사용되는 FIR형태의 머리전달함수는 높은 차수를 가지고 있어 실시간 음상정위 처리가 어려운 문제점을 가지고 있다. 본 논문에서는 FIR 형태의 머리전달함수를 ARMA 시스템 인지기법을 이용하여 저차의 IIR필터 형태로 모델링하여 실시간 데이터 처리가 가능하도록 하였다. 본 논문에서 제안하는 ARMA 시스템 인지기법을 이용하게 되면 주어진 고차의 FIR형태의 머리전달함수를 다양한 안정성을 갖는 IIR모델들을 얻을 수 있으며, 이들 중 적절한 스펙트럼오차를 갖는 저차의 IIR모델을 선택 할 수 있다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.269-272
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• 1998

본 논문에서는 스테레오 스피커를 통해 입체 음향을 재생할 때 발생하는 크로스 토크(corss talk)를 제거하기 위한 트랜스오럴 필터를 실시간으로 구현하였다. 실시간 처리를 위하여 일반적인 트랜스오럴 필터를 재구성하였으며, 범용 DSP(Digital Signal Processor) 칩인 TMS320C40을 사용하였다. 메인 프로그램은 C-언어를 이용하여 작성하였으며, 빠른 연산을 필요로 하는 컨벌루션 함수는 어셈블러 언어를 이용하여 최적화 하였다. 구현된 트랜스오럴 필터의 평가를 위해서 더미 헤드를 이용하여 녹음된 binaural 신호와 DSP를 이용하여 실시간으로 합성된 binaural 신호를 스테레오 스피커를 통해 재생하여 청취 실험하였다. 청취 실험한 결과 머리 밖에서 음상 정위가 이루어지고 공간감과 거리감은 헤드폰으로 청취할 때 보다 우수하게 나타났다.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1998.04a
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• pp.212-216
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• 1998

청취자가 음원의 위치와 방향을 감지할 수 있도록 원하는 지점에 음상을 정위시키는 일과 특정 공간내에서 방사되는 음원의 반사와 확산효과를 모델링하여 가상 공간 음향을 실현하는 일을 효과적으로 접목시키기 위한 3가지 유형의 입체음향 생성방법을 제시한다. 그리고 각 방법의 유효성 및 적합성을 검토하기 위해 실시한 심리음향 평가방법과 그에 대한 결과를 토대로 생성발법들간의 성능을 비교 평가한다.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1999.11a
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• pp.101-104
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• 1999

완벽한 가상 현실을 재현하려면 사람의 오감을 실제 세계 수준으로 정교하게 재현해야 한다. 현재 시각 효과는 상당히 발전해 있으나, 청각적, 음향적 부분은 아직도 발전 정도가 상대적으로 낮다. 가상 현실을 위한 음향은 크게 HRTF등을 이용한 음상 정위와, 음장 재현으로 나눌 수 있다. 본 논문에서는 가상 현실 체험자의 이동에 따라 효과적으로 음장을 재현하는 방법에 대해 논하고자 한다. 본 논문에서 제안하는 시스템은 크게 전처리 부분과 실시간 처리 부분으로 구성되어 있으며 전처리 과정에서 음장을 계산하여 실시간 처리 부분에서 체험자의 위치를 추적하여 음장을 재현한다.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.43-46
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• 2013

Active use of images in the same place as the religion according to the height of the screen is determined by the height of the main speakers. This causes the 'sound image mismatch' and 'bass boost' sound like a failure occurs. Front seats are good seats in visual acoustics is a bad place. To minimize these obstacles acoustical speakers to actively apply the front fill needed. Higher sound pressure difference between the main speaker and the distance must be determined in accordance with the appropriate capacity. Actively using the front speakers to the sound image field by implementing the agreement to increase the concentration of sound. The relatively high inflow enhance alto lacking the front seat can be implemented evenly in the frequency response. Column in front of the main seat of the main speakers to supplement the deficiencies can be implemented more comfortable acoustic environment. Front fill speaker needs to be actively introduced, thereby presenting a detailed estimate, is needed.

• 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.30 no.5
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• pp.255-264
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• 2011

The Head Related Transfer Function (HRTF) means a process related to acoustic transmission from 3d space to the listener's ear. In other words, it contains the information that human can perceive locations of sound sources. So, we make virtual 3d sound using HRTF, despite it doesn't actually exist. But, it can deteriorate some three-dimensional effect by the confusion between front and back directions due to the non-individual HRTF depending on each listener. In this paper, we proposed the new algorithm to reduce the confusion of sound image localization using human's acoustic characteristics. The frequency spectrum and global masking threshold of 3d sounds using HRTF are used to calculate the psychoacoustical differences among each directions. And perceptible cues in each critical band are boosted to create effective 3d sound. As a result, we can make the improved 3d sound, and the performances are much better than conventional methods.

• Journal of the Institute of Convergence Signal Processing
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• v.12 no.1
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• pp.1-6
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• 2011

In this study, we investigated the effect of the simplification for high frequency region in Head-Related Transfer Function(HRTF) on the sound localization. For this purpose, HRTF was measured and analyzed. The result in the HRTF frequency characteristic of the back sound source showed that the decrease revel of high frequency was smaller than that of low frequency region, which means the possibility of simplification in the high frequency region. Simplification was performed by flattening of the high frequency amplitude characteristics with the insertion of the low-pass filter, whose cutoff frequency is given by boundary frequency. Auditory experiments were performed to evaluate the simplified HRTF. The result showed that direction perception was not influenced by the simplification of the frequency characteristics of HRTF for the error of sound localization. The rate of confusion for the front and back was not affected by the simplification of the frequency characteristics over 8kHz of HRTF. Finally, we made it clear that the sound localization was not affected by the simplification of frequency characteristics of HRTF over 8kHz.

• The Journal of the Acoustical Society of Korea
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• v.28 no.6
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• pp.557-565
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• 2009

To perceive the direction and the distance of a sound, we always use a couple of information. Head Related Transfer Function (HRTF) contains the information that sound arrives from a sound source to the ears of the listener, like differences of level, phase and frequency spectrum. For a reproduction system using 2 channels, we apply HRTF to many algorithms which make 3d sound. But it causes a problem to localize a sound source around a certain places which is called the cone-of-confusion. In this paper, we proposed the new algorithm to reduce the confusion of sound image localization. The difference of frequency spectrum and psychoacoustics theory are used to boost the spectral cue among each directions. To confirm the performance of the algorithm, informal listening tests are carried out. As a result, we can make the improved 3d sound in 2 channel system based on a headphone. Also sound quality of improved 3d sound is much better than conventional methods.