• Journal of KSNVE
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• v.2 no.2
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• pp.92-95
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• 1992

자동차에 사용되는 경음기는 자동차들 사이뿐만 아니라 특히 보행자에게 경적음을 발생하여 사고를 사전에 방지하기 위하여 사용되는 자동차의 필수 부품 이다. 일반적으로 경음기는 2가지 특성에 의해 특정지워 질 수 있는데 이는 음압과 주파수(음색) 특성이다. 이들 모두는 규격에 의하여 제한되는 요소들로서, 전자의 경우 너무 소리가 적게되면 경음기로서의 기능을 상실하게 되며 지나치게 크게 되면 상대방 및 주위에 지나치게 크게 피해를 주게 되는 요소이다. 후자의 경우 동일한 크기의 음압이라도 그것을 구성하는 특성에 따라 인간에게 주어지는 소음에 의한 심리적 영향이 달라지게 되므로 불쾌음의 발생을 지양해야 한다. 이 글에서는 같은 음의 세기라도 상대적으로 부드러운 음색을 갖는 셸(shell)형 경음기의 특성 및 개발 결과에 대하여 언급하고자 한다.

• Journal of KSNVE
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• v.10 no.2
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• pp.345-352
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• 2000

Recently, it becomes to be very important to reduce the cabin noise of passenger ship, according to the trend of speedy and luxury ship. The noise reduction and control techniques should be considered as important factors from the viewpoint of the sound problem of cabin. Therefore, ship designer has to improve the sound quality as well as to redece the sound pressure level in cabins. In this paper, for the new approach of these problems, we tried to find the trends of noise and sound quality of high-speed coastal passenger ships. Loudness, roughness, fluctuation strength, and sharpness are selected as the parameters for the evaluation of sound quality. The parameters are calculated by using the sound measured in cabin while the ship is running. Furthermore we tried to find the trend of each parameter in cabins and compare with that of sound pressure level. As results, we find that the loudness is linearly proportional to sound pressure level. But, the other parameters show different trends which may be caused by ship motion on the wave and fluctuation of propelling power.

• 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..

• Journal of the Korean Society of Clothing and Textiles
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• v.25 no.9
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• pp.1593-1602
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• 2001

본 연구는 스포츠 아우터웨어용 나일론 직물의 소리에 대한 주관적 감각과 이에 관련된 객관적 측정치를 규명하기 위하여, 서로 다른 8종의 나일론 직물의 소리의 스펙트럼 파형을 고찰하였으며, 소리 파라미터로 총음압(level pressure of total sound, LPT),세 가지 AR (autoregressive)계수, Zwicker의 심리음향학적 모델에 따른 크기(Z)와 날카로움(Z)를 계산하였고, Kawabata Evaluation System(KES)으로 직물의 물리적 성질을 측정하였다. 주관적 감각 평가를 위하여 피험자에게 녹음된 각 직물소리를 들려주어 7개 소리 감각 (부드러움, 시끄러움, 날카로움, 맑음, 거 침, 높음, 유쾌함)을 의미분별척도로 답하게 한 후, 단계적 선형 회귀식을 이용하여 직물 소리의 주관적 감각에 대한 예측 모델을 제시하였다. 울트라스웨이드를 제외한 태피터 나일론 직물들은 스펙트럼 파형 에서 다른 조성 섬유의 직물들보다 음압 값이 높고, 총음압이 60dB 안팎의 값을 보여, 착용자에게 불쾌감을 줄 것으로 예상되었으며, 주관적 감각 평가에서도 소리의 부드러움과 맑음, 유쾌함에서 음의 점수를, 시끄러움과 날카로움, 거침, 높음에서 양의 점수를 얻었다. 주관적 감각의 예측모델에서 총음압은 시끄러움과 거침에 정적 영향을, 유쾌함에 부적 영향을 미쳐서 나일론 직물 소리의 총음압이 50dB 이하일 때 주관적으로 유쾌하게 느껴지는 것으로 나타났다.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2001.05a
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• pp.54-59
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• 2001

본 연구는 청각적 감성을 만족시키는 의류소재의 개발을 위해, 직물 마찰음에 대한 인간의 감서을 생리반응측정과 심리적·주관적 평가를 통해 파악하고, 직물 마찰음이 갖는 음향특성과의 관련성을 고찰하였다. 이를 위해 직물 마찰음의 음향특성을 분석하고, 직물 마찰음에 대한 감각·감성 표현어(부드러움, 시끄러움, 유쾌함, 날카로움, 맑음, 거침, 높음)를 이용하여 주관적 평가를 실시하였으며, 생리적 반응으로서의 뇌파 및 혈류량, 심박변화율, 피부전도수준 등을 측정하였다. 주관적 감각·감성은 대부분 직물 소리의 크기와 관련이 깊은 것으로 나타나, loudness(Z)와 총음압 LPT가 증가할수록 시끄럽고 거칠며 딱딱하고 불쾌하며 탁하다고 지각하였다. 생리적 반응과 관련하여서는, 부드럽고 조용하며 맑다고 지각할수록 slow alpha파가 증가하였고, 유쾌하고 매끄럽다고 평가할수록 혈류량은 증가하였다. 또한, 높다고 지각하는 소리에 대한 LF/HF는 증가하였다. 마찰음의 음향특성이 생리적 반응에 미치는 영향으로서, LPT가 혈류량의 감소에, Loudness(Z)가 피부전도수준의 증가에 각각 영향을 미치며, sharpness(Z)가 높고 ΔL이 작을수록 LF/HF는 증가하는 것으로 나타났다.

• Journal of the Korean Institute of Gas
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• v.13 no.1
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• pp.9-13
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• 2009

A cause of noise and vibration which come from a Combustion of gas heater are a combustion roar and Combustion oscillation. A character of a combustion roar is that sound pressure is distribute with broad band frequency. otherwise, The presence of combustion oscillation caused by positive Feed Back in Combustion Chamber break out a noise and vibration. Accordingly, The method that be solved a noise and vibration is to make each natural frequency different frequency. first, in order to solve problem, we control ratio of fuel and air. that is, Keep away resonance. second, in order to changing natural frequency of Combustion Chamber, We changed the shape of Economizer.

• The Journal of the Acoustical Society of Korea
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• v.32 no.5
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• pp.402-407
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• 2013

In this paper, an analysis of sound propagation between two rooms with different mediums is discussed. Statistical energy analysis (SEA) is used to consider energy equilibrium among subsystems associated with the sound pressure levels in two rooms and the vibration level of the wall between rooms. Effect of the sound radiation from the structure-borne noise of the wall on sound pressure level of the receiving room is investigated. For a numerical example, sound propagation between engine room and water tank joined by a steel plate whose size is $8.4{\times}4$ m, is considered. It is found that when the critical frequency of the plate is above the frequency range of interest, the sound pressure level in the water tank is dominated by sound transmission through the plate, while sound radiation from the structure-borne noise of the plate is negligible except low frequency range below 63 Hz.

• Science of Emotion and Sensibility
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• v.4 no.2
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• pp.79-88
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• 2001

The objectives of this study were to investigate the relationship of sound parameters with subjective sensation and physiological responses, and to figure out the interrelationship between the subjective sensation and physiological responses. Sound parameters calculated were LPT, ΔL, Δf, loudness[Z], and sharpness[Z]. Subjective sensation was evaluated in 7 aspects(soft-hard, loud-quiet, pleasant-unpleasant, sharp-dull, clear-obscure, rough-smooth, high-low) by thirty participants. We acquired physiological responses when each fabric sound was presented to 10 participants. Physiological signals obtained in this study were electroencephalogram(EEG), pulse volume(PV), skin conductance level(SCL), and LF/HF of heart rate variability. The larger the values of loudness[Z] and LPT, the louder and the rougher the subjective sensation of the perceived fabric sound. Also, the larger the values of loudness[Z] and LPT, the harder, the duller, and the less pleasant. As LPT increased, PV decreased. Loudness[Z] increased in proportion to SCL and so did sharpness[Z] to LF/HF. As the sound perceived to be quieter and clearer, the relative power of slow alpha rose. As the sound perceived to be more pleasant and smoother, PV rose.

• Journal of the Korean Society of Combustion
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• v.3 no.1
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• pp.59-69
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• 1998

The results of study on the active control of naturally occurring combustion oscillations with a single dominant frequency in an atmospheric dump combustor are presented. Control was achieved by an oscillatory infection of secondary fuel at the dump plane. A high speed solenoid valve with a maximum frequency of 250Hz was used as the actuator and a sound level meter, located at the combustor exit, measured the pressure fluctuations which served as the feedback signal for the control loop. Instability characteristics were mapped over a range of mean mixing section velocities from 6.7 m/s-9.3 m/s and with three mixing conditions. Different fuel/air mixing conditions were investigated by introducing varying percentages of primary fuel at two locations, one at the entrance to the mixing section and one 6 mixing tube diameters upstream of the dump plane. Control studies were conducted at a mean velocity of 9.3 m/s, with an air temperature of $415^{\circ}C$, and from flame blowout to the stoichiometric condition.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.853-858
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• 2001

The knowledge of flame structure is essential for control of combustion instability phenomena. Some results of an experimental study on mechanism of naturally occurring combustion oscillations with a single dominant frequency are presented. Tests were conducted in a laboratory-scale dump combustor at atmospheric pressure. Sound level meter was used to track the pressure wave inside the combustor. The observed instability was a longitudinal mode with a frequency of $\sim341.8Hz$. Instability map was obtained at the condition of inlet temperature of $360^{\circ}C$, mean velocities of $8.5\sim10.8m/s$ and well premixed mixture. It showed that combustion instability was susceptible to occur in the lean conditions. In this study, unstable flame was observed from stoichiometric to 0.7 in overall equivalence ratio. At selected unstable conditions, phase-resolved OH chemiluminescence images were captured to investigate flame structure with various mean velocities. As mean velocity is increased, the flame grows and global heat release was changed. Due to these effects, combustion instability can be maintained at more lean air-fuel ratio. Also, these results give an insight to the controlling mechanism for an increasing heat release at maximum pressure.