• Korean Journal of Materials Research
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• v.19 no.7
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• pp.382-385
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• 2009

Efforts to reduce noise in industrial application fields, such as automobiles, aircrafts, and plants have been gaining considerable attention while a sound proof wall to protect people from the noise has been intensively investigated by many researchers. In this study, our research group suggested creating a new sound proof wall composed of scrap aluminum chips and perforated plates in a commercial polyester sound proof wall, which was then successfully fabricated. This wall's sound absorption characteristics were measured by an impedance tube method. The sound absorption property was evaluated by measuring the Noise Reduction Coefficient (NRC) to the standard, ASTM C 423-90a. The noise reduction coefficient of the sound proof wall composed of 3.5 vol.% and 7.5 vol.% of scrap aluminum chips relatively increased to 5% and 8% compared to the commercial polyester sound proof wall. The scrap aluminum perforated plate also relatively increased to 13% compared to the commercial polyester sound proof wall.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.145-149
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• 2001

In this study, an acoustical characteristics of sound proof panel for high speed train was performed. A sound absorption coefficient and transmission loss of sound proof panels for high speed train were tested in reverberation chambers and compared those of ordinary sound proof panel. The effect of noise barrier was simulated by using ray noise program with measured sound absorption coefficient for high speed train case and for ordinary case.

• Journal of Environmental Health Sciences
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• v.21 no.4
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• pp.56-62
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• 1995

Recently, the traffic noise around residences and schools has become a serious social problem with the increase of the amount of transportation. This study was performed to investigate the sound proof efficiency of windows for traffic noise. The results were as follows 1) The traffic noise in 19 sites among 22 sampling sites was higher value than 65 dB(A) being roadside environment standard level in the daytime when all windows were opened, while the noise in 22 sampling sites was transmitted below standard level when all windows were closed. 2) The transmission loss of sound level at single window and double windows were 10~25 dB(A) and 11~29 dB(A) respectively. 3) The transmission loss of sound level at sampled school with sound proof pannel was 7~8 dB (A), which was lower 2~7 dB(A) than the theoretical value of the influence assessment . 4) The construction cost of double windows was lower 28% even if include the cost of setting up air conditioner for the summer season and the power consuming cost for its operation than that of sound proof pannel for traffic noise. 5) The effect of transmission loss of windows was more influenced by airtight than materials of windows.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.125-130
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• 2014

High speed railroad car and high-rise apartment with development of railway technology cause different problems of noise contrary to the previous generation. It is the most efficient noise reduction countermeasure but we studied that is the way on noise propagation with sound proof wall or sound proof tunnel around railroad. But if it were railroad on bridge, additional cost which is more expensive than installing one on the ground is needed. So sound insulation material considering reducing weight of recent soundproof facilities must be selected. It is in this study that predicted and analyzed acoustical and structural effect for noise reduction by installing soundproof tunnel. If it were departmentalized into additional study, could be able to expect noise reduction effect of sound proof tunnel establishment on the bridge.

• Journal of the Korean Society for Advanced Composite Structures
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• v.7 no.1
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• pp.19-24
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• 2016

Most of the soundproof tunnels generate significant discharge noise through their inlets and outlets so that the length of the tunnel has been extended frequently than required to minimize the effect on such discharge noise. Thus, in this paper, we investigate reduction capability of discharge noise from the sound proof tunnel installed with lateral sound-absorbing panels on the partitioned truss members in the longitudinal direction of the tunnel. In conclusion, noise field analysis results shows that the sound proof tunnels with lateral sound-absorbing panels have an effect on discharge noise abatement and thereby tunnel's length reduction.

• Journal of KSNVE
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• v.8 no.6
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• pp.1043-1052
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• 1998

The noise sources in the outdoor unit of RAC are identified by the sound intensity method. The main noise sources are compressor noise and fluid noise which is caused by the fan. heat exchanger and shroud. First. the fluid noise is reduced through the design of new fan and shroud. reduction of the system resistance by rearrangement of heat exchanger. and optimization of the complex parameter between the fan and shroud. Next, in order to reduce the compressor noise, the new shape of compressor mount and sound-proof material was applied. As a result, the overall noise was reduced by 4∼5dB (A).

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.529-544
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• 2007

After rapid running is begun in domestic, problem by the train gust that was not considered at existent train running appeared. If the High-Speed railway business speed rises by 350km/h in the future, is going to become more big problem. This study conducts an experiment that measure in local about KTX train beside Gyeong-Bu High speed railroad track about aerodynamics effect that happen by passage of train and analyzed. In case KTX II runs with the 350km/h speed, forecasted effect that get in the simple vertical surfaces parallel to tracks according to distance from rail center. Compared construction size with structural analysis in case do not consider with case that consider the train gust about sound proof walls representatively. As a result, proposed wind load standard that apply at sound proof walls design.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.687-691
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• 2007

It is important to increase the sound proof performance of building for reducing the influence of aircraft noise on the bais of actual survey of existed buildings. The purpose of this study is to propose the basic data for designing sound insulation of residential house. In this study, field measurement of aircraft noise Interior and outside noise level difference were carried out for 7 days in 2 residential houses. As the result, aircraft noise levels showed to be Leq $71.8{\sim}74.5$dB(A), WECPNL $82.2{\sim}83.4$ and indoor noise level were NC-55 ${\sim}63$ over acceptable NC-30 in 2 measured houses. Noise reduction effect showed to be $15.8{\sim}23.1$dB(A) in measured houses, and houses with double window were preferable to those with single window in sound proof performance. The outside sound pressure level for residential house was a little different according to the type of source. In measuring by using aircraft noise it was effected by angle and distance from measuring point, to aircraft, window area, and sound absorption of room, and so on.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2546-2551
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• 2007

Weather Strip(W/S) is a rubber part to proof water, sound and dust for opening and shutting devices including vehicle doors. And it requires high dimension precision and durability to proof water, noise, vibration and etc. But ironically it itself makes some wind noise because of some protuberance with glasses. The air flow analysis of door part of vehicle makes it possible to calculate and find out the cause of wind noise. In previous analysis, we focus on the numerical air flow analysis of the automobile side part. We do 2D-C.F.D first and 3D second. Through simulations, we can calculate the amount of sound pressure level at the glass run and find out the effects of glass run to make wind noise. Finally we can improve shape of glass run to reduce wind noise although it is small amounts of sound pressure reduction compared with total vehicle noise level.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.100-102
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• 2009

Effect of temperature, pH and soil depth on germination of Dianthus chinensis, Dianthus barbatus, and Perennial pennant were investigated in growth chamber and soil condition at the ratio of 7:3 (natural soil and organic soil) in laboratory condition. the optimum temperature for seed germination was recorded for $20^{\circ}C-\;25^{\circ}C$. Maximum germination was observed for Dianthus barbatus (76%) where as in soil condition Perennial pennant (51%) showed maximum germination at 1 cm soil depth. Similarly, optimum pH for seed germination was at pH 6 in all the species. So in lower pH (at pH4) seed germination was inhibited. Germination of these selected species at different environmental condition help to construct the ecological sound proof wall to mitigate the noise especially in urban areas.