• The Journal of the Acoustical Society of Korea
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• v.33 no.1
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• pp.10-20
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• 2014

To study the water-entry impact noise, on-board experiment using a small launcher firing various objects was performed in the Yellow Sea. As the launcher fires a cylindrical object from the ship vertically, generated noise is measured with a hydrophone on the starboard of Chung-hae, Marine surveyor. Three types of cylindrical objects, which have noses of flat-faced, conical, and hemisphere, were used during the experiment. The measured noise exhibits a time-dependency which can be divided into three phases: (1) initial impact phase, (2) open cavity flow phase, (3) cavity collapse and bubble oscillation phase. In most cases, the waveform of bubble oscillation phase is dominant rather than that of initial impact phase. Pinch-off time, where a cavity begins to collapse, occurs at 0.18 ~ 0.2 second and the average lasting time of bubble was 0.9 ~ 1.3 second. The energy of water-entry impact noise is focused in the frequency region lower than 100 Hz, and the generated noise is influenced by the nose shapes, object mass, and launching velocity. As a result, energy spectral density on the bubble frequency is higher in the order of flat-faced, conical, hemisphere nose, and the increase of initial energy raises the energy spectral density on the bubble frequency in the cylinder body of same shape. Finally, we compare the measurements with the simulated signals and spectrum based on the bubble explosion physics, and obtain satisfactory agreements between them.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.856-857
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• 2014

국내에서 이용되는 예측모델은 국립환경과학원식, 도로공사의 HW-NOISE, KHTN, 소음지도에 이용되는 외국의 RLS90, NMPB 등이 있다. 이러한 예측모델은 예측 방법 및 표현에 따라 예측식 2D(국립환경과학원식, HW-NOISE)와 3D로 예측(KHTN, RLS90, NMPB 등)으로 구분할 수 있다. 본 연구는 도로 주변 공동주택에서의 소음실측 및 예측식별 예측값을 통하여 예측식의 오차 및 오차의 원인을 분석하고 예측식의 적용방법에 대하여 고찰하였다.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.1
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• pp.67-73
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• 2006

10 sites in building development areas were selected and the noise level were measured by the apartment floors of apartment complex. With the fitted regression analysis, the distribution ratio($R^2$) and correction coefficient(r) was 25%(0.5) in the NIER('87) and 7.5%(0.274) in the NIER('99), respectively. The measured values of the noise level on the seventh floor of complex did not show a good agreement with the predicted noise level in the NIER('87, '99) formula. However, the developed formula demonstrated that the measured values were reasonably close to the predicted values, indicating the validity and adequacy of the predicted models with the fitted vs residual analysis in the 95% of confidence interval and 95% of predict interval. The results suggested that application of this development model obtained by the results according to the apartment floor can be improved in road traffic noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1991.04a
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• pp.53-56
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• 1991

산업구조의 급속한 발전과 공업화는 사회구조의 변화 및 대도시로의 인구집 중, 고밀도화, 교통량의 증가를 초래하여 이로부터 기인한 도시지역의 환경 오염 문제는 쾌적한 인간생활을 위협하는 단계에까지 이르렀다. 그중에서 소 음에 관한 문제도 대기 및 수질의 오염과 동시에 도시생활 환경에 많은 영 향을 미치게 되었다. 도시 소음의 주 원인은 주로 도로교통소음이며 이는 기 하급수적으로 늘어가는 자동차의 양에 의해 더욱 심해지고 있다. 따라서 현 재 우리나라에서도 주거지역 및 준주거지역 등의 지역별 소음도 규제 및 신 설되는 공동주택 단지에서의 소음레벨규제등이 있긴 하나 이들은 상당히 소 극적이며 미온적일 뿐 아니라 실제 거주하는 주민들의 반응과는 상당한 차 이를 보이고 있으며 더욱이 주민의 소음에 대한 주관적 반응을 적절히 표현 할 수 있는 지표마저 명확하지 않은 실정이다. 이러한 관점에서 본 고찰에서 는 피험자들의 주관적 반응을 실험할 때 발생하는 변수요인들을 통제 할 수 있는 실험 실시행 청감실험을 실시하기에 앞서 대상지역의 도로교통소음을 여러가지 평가척도에 의해 평가한 후 그 현장에서 이 소음에 노출된 피험자 들의 반응을 파악하여 청취자들이 인지하는 소음레벨을 적절히 평가하는 지 표를 찾고자 한다.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.1
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• pp.13-19
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• 1995

The objective of this study is do obtain the relationship between the acoustic mode and cavity tone induced in a perforated tube exhaust muffler. First, the modal frequency for the axisymmetric radial mode and the mode shape have been computed using the impedance model for the perforated tube. Then, experiment has been perfonned for the onset frequencies of the cavity tone for various design parameters and through-flow. The theoretically obtained modal frequencies are well consistent with the measured onset frequencies of the cavity tone, showing that the cavity tone is induced by the axisymmetric radial mode. And it is found that the modal frequency of a perforated tube muffler is much lower than that of a simple expansion chamber.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.7
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• pp.685-692
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• 2009

Vehicle interior noise is the results of numerous sources of excitation. One source involving tire pavement interaction is the tire cavity resonance and the forcing it provides to the vehicle spindle. Using a simplified model for the tire acoustic cavity system only, we formulated finite element equation to predict the fundamental acoustic cavity resonant characteristics inside tire-wheel assembly of undeformed and deformed tire. Combining the finite element analysis with experimental verification, we explained the acoustic characteristics theoretically. Especially, we have shown that the difference between the first two resonant frequencies increases as the deformation of deformed tire increases.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.551-556
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• 2009

Vehicle interior noise is the results of numerous sources of excitation. One source involving tire pavement interaction is the tire cavity resonance and the forcing it provides to the vehicle spindle. Using a simplified model for the tire acoustic cavity system only, we formulated finite element equation to predict the fundamental acoustic cavity resonant characteristics inside tire-wheel assembly of undeformed and deformed tire. Combining the finite element analysis with experimental verification, we explained the acoustic characteristics theoretically. Especially, we have shown that the difference between the first two resonant frequencies increases as the deformation of tire due to vertical load increases.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.11
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• pp.1137-1146
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• 2004

In an apartment house In Korea, the balcony is one of the important spaces as a buffer zone for controlling the outdoor environments such as noise, heating & cooling load, humidity etc. Because most areas of building facade in apartment building occupy the area of balcony window the sound Insulation design of It Is very Important to provide the quiet indoor environment. The aim of this research is to evaluate the sound insulation of balcony windows in apartment building by new and revised Korean Industrial Standards. We measured and studied the sound insulations of 18 balcony windows by the type of measuring methods, noise sources, correction of reverberation time in balcony and so on. The results show that the single-number quantities for sound insulation of windows are ranged from 24 dB to 30 dB.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.844-847
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• 2008

As customer's demands are varying, the type of floor plan of apartment is changed into expanded type with balcony unified to living room from general type with balcony separated from living room and so is changing the layout of L(living room), D(dining room) and K(kitchen). This study aims to examine how the type of floor plan of living room affects the floor impact sound insulation performance and to propose fundamental idea to floor plan layout of apartment in terms of floor impact sound reduction.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.2
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• pp.179-184
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• 2010

In this study, the satisfaction rating to the floor impact sound was investigated for the residents in the apartment Building where the business scheme had been approved after 2005. The results are compared with existing research. The questionnaire survey was conducted to the 597 residents in 14 apartments complex which were applied with standard floor structure and approval floor structure. Most of respondents(71.1 %) answered that the performance of floor impact sound insulation, in case of standard floor structure, was improved compared to the apartments where they used to live. Comparing with the questionnaire survey result of existing research, the answered ratio of 'less annoyed' and 'less loud' is somewhat increased.