• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.287-290
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• 2000

In periodic structures where two or more materials of different density and sound speeds are arranged, there exist stop bands, in which waves cannot propagate. In this paper noise and vibration reduction by using band gap phenomena is discussed. The general theoretical background is presented and experimental results for acoustic wave attenuation in 2D cylinder arrays are described.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.217-220
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• 2004

본 논문에서는 다중 wedge와 방음벽에 의한 음파의 회절을 예측하는 공식을 다루었으며 BEM이나 다른 측정결과와 비교하여 정확성을 확인하였다. 여러 가지 경우의 회절경로가 있을 때 가장 적은 수의 회절경로를 따라 전파하는 음파가 가장 중요한 성분이며 회절수가 커질수록 크기는 줄어든다.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.317-320
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• 2004

본 논문에서는 2004 년도 춘계학회에 발표한 다중 wedge와 방음벽에 의한 음파의 회절 계산방법[1]을 여러가지 형태의 방음벽에 적용하였으며 BEM과 비교하여 정확성을 확인하였다. 상단 일부가 꺾인 방음벽에 대해 꺾는 각도, 길이변화에 따른 삽입손실을 계산하였으며 여러가지 높이의 수음점에 대해 회절을 계산하였다.

• The Journal of the Acoustical Society of Korea
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• v.23 no.2E
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• pp.44-50
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• 2004

A theoretical formula that is based on the geometrical theory of diffraction (GTD) is proposed for computing sound diffraction by multiple wedges, barriers, and polygonal-like shapes. The formula can treat both convex and concave edges, where edges mayor may not be inter-connected. Comparisons of theoretical predictions with other results done by the BEM or experiments for scaled model confirm the accuracy of the present formula. Numerical examples such as double wedges and doubly inclined barrier show that when there exist several diffraction paths for given source and receiver positions, the insertion loss is dominated by the diffraction associated with the shortest propagation path.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.461-461
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• 2010

The history of architectural acoustics is a part of history of human being getting together for both politics and entertainments, is also a part of the history of nobility pursuing hearing enjoyments, is still a part history of scientists deeply understanding the concept of "just for people", and as well as is a part history ceaselessly driven by the musicians to find their real hearts through music. The history of architectural acoustics explains not only the acoustic knowledge developments in architectural design, but also the unity on contradictory of both the science and the arts, both the technology and the culture, both the sense and sense organ. The history of architectural acoustics prints the interactions between the mankind and the nature, between the mankind and themselves, between the mankind and their souls, in which course people understand their feelings more deeply and deeply. This paper discusses the brief history of architectural acoustic in China from the ancient drama stages to grand theaters in 20 century, even up to nowadays, including some most important buildings and events as well.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.367-370
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• 2001

Various shapes of the noise barrier frame and construction of the sound absorbing panels are studied. It is found that insertion of the sound absorbing panel into barrier frame results in the decrease of the sound absorption coefficient, while the empty frame shows a peak around 250Hz. Using double sound absorbing panels with air gap can increase sound absorption coefficient up to NRC 0.85.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.461-468
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• 2002

Prediction method of floor impact noise for light and heavy weight impact is described. Sound pressure level is predicted based on the impedance method. For floating floor system, noise reduction is studied assuming 1-D mass-spring system. It is found that comparisons of predictions and measurements show good agreements. However, certain correction factor is needed to predict noise reduction of floating floor system.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.1
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• pp.24-33
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• 2004

Recently, ship acoustics takes more important role in acoustic stealth and classification of underwater targets. In this paper, a theoretical concept is proposed for M＆S-based test and evaluation of ship acoustics. The concept is based on two different approaches: on Top-Down method which emphasizes the survivability of the ship and on Bottom-Up method which considers acoustic characteristics of the ship-equipments. In order to improve the effectiveness of M＆S-based T＆E for ship acoustics, it is recommended in this paper to compromise the two approaches as adequate.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.1
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• pp.1-8
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• 2016

Single crystalline silicon wafers having (100), (110), and (111) directions are employed as specimens for obtaining slowness profiles. Leaky Lamb waves (LLW) from immersed wafers were detected by varying the incident angles of the specimens and rotating the specimens. From an analysis of LLW signals for different propagation directions and phase velocities of each specimen, slowness profiles were obtained, which showed a unique symmetry with different symmetric axes. Slowness profiles were compared with elastic moduli of each wafer. They showed the same symmetries as crystal structures. In addition, slowness profiles showed expected patterns and values that can be inferred from elastic moduli. This implies that slowness profiles can be used to examine crystal structures of anisotropic solids.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.10
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• pp.148-158
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• 2015

It is difficult to test a detection system in underwater acoustics channel environments. The system can be evaluated by using simulation analysis tool. In this paper, a simulation tool is proposed to analyze the effectiveness of underwater acoustics detection based on database for real environments. First, the underwater environment is built based on HYCOM underwater environment database. Then, a multipath characteristic is considered through calculating underwater acoustics propagation path/pressure based on the ray theory. Also, hydrophone thermal noise and underwater ambient noise are considered to reflect underwater noise characteristics.