• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.1083-1087
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• 2001

The purpose of this study is to obtain the basic data of existing light-weight Drywall through the evaluation and analysis of the light-weight drywall in reverberation chamber and to improve sound insulation performance of drywalls. Sound transmission loss of the total 11 types were analyzed in each frequency a-third octave band and evaluated sound insulation performance for each frequency. From data by analysis and calculation, STC value plotted on STC contour. We found that the improved light-weight drywall specimens ⓑ, ⓒ and ⓖ were satisfied with the domestic standard of sound transmission loss.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.93-96
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• 2004

In the case of the front door of the apartment, which functions as an entrance, the study about noise has been less active than corridor type plane in the past, since stair room type plane was generalized. Hence, this study shows the survey about residents' thoughts of noise transmission through the front door, and after researching sound insulation of the present apartments, we figured out what the problem is. Moreover, we did an efficiency test as developing the front door, which increases sound insulation. As a result, it turned out that residents think that the noise transmission through the front door is as serious as floor impact noise, and also, the efficiency of the front door is as poor as STC 22-30. Therefore, in the developed front door, we should improve the efficiency to the level of STCSS. It will be a good way preparing for a demand of residents.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2002.05a
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• pp.209-212
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• 2002

This article introduce Comfort Class V released by Dnv The Class has an objective of classifying ships by noise and vibration levees. It is apparent that noise criteria listed in the Class can not be satisfied without special efforts to enhance sound insulation performance in cabins. Accordingly, panel makers should develope panels which have very high sound insulation performance enough to satisfy the criteria. Also, due to large difference of sound insulation performance between cabin and laboratory, it is necessary that ship yards should improve the method for installing cabins.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.421-424
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• 2000

This paper investigates the characteristics of analytical models in prediction of sound transmission loss for the multi-layered panels with high density mineral wools. The results show that the sandwich model is more adequate to account for sound insulation performance of those panels than the poro-elastic model. In order to improve STC(Sound Transmission Class), the effect of fiber directions of mineral wools is examined, analytically and experimentally. From the comparison of the measurements with the predictions, it is evident that the vertical fiber directions of mineral wools enhance STC value up to 6 dB, compared to that of the horizontal fiber directions.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.6
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• pp.362-371
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• 2022

As considerable interests in noise emission from the ships have been increased, International Maritime Organization (IMO) standardized the Underwater Radiated Noise (URN) measurement process of commercial ships in deep seas by enacting the related ISO standard ISO 17208-1 and classification societies responded with the enactment or revision of corresponding notations. According to this trend, a new hybrid underwater sound propagation model based on underwater sound propagation theories was developed and its accuracy on analysis was verified through the result comparison with the results of other generally used models. Using the verified model, each URN propagation characteristics adjusted by the correction methods proposed in the ISO standard and class notations were analyzed and compared in two assumed URN measurement cases. The results showed that the effects of transmission loss corrections in the circumstances with less bottom reflections generally similar but they had rather large differences in the model analysis results with bottom-reflection-dominant conditions. It was concluded that the deep consideration of effective bottom-reflection-correction method should be made in future revisions of ISO standard and class notations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.3C
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• pp.234-239
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• 2008

For the efficient coding and transmission, the speech signal can be classified into three distinctive classes: voiced, unvoiced, and transition classes. At low bit rate coding below 4 kbit/s, conventional sinusoidal transform coders synthesize speech of high quality for the purely voiced and unvoiced classes, whereas not for the transition class. The transition class including plosive sound and abrupt voiced-onset has the lack of periodicity, thus it is often classified and synthesized as the unvoiced class. In this paper, the efficient algorithm for the transition class detection is proposed, which demonstrates superior detection performance not only for clean speech but for noisy speech. For the detected transition frame, phase information is transmitted instead of magnitude information for speech synthesis. From the listening test, it was shown that the proposed algorithm produces better speech quality than the conventional one.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.374.1-374
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• 2002

The eventual purpose of this research is to make optimum standards for acoustic-environment by using not only physical characteristics but also subjective appraisals. First, basic Physical data were measured which were necessary to establish standards for acoustic environment in campus buildings, TSP has used to measure sound levels, reverberation times, clearness indexes, and speech-transmission-index. (omitted)

• The Journal of the Acoustical Society of Korea
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• v.36 no.5
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• pp.329-337
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• 2017

In USA and UK, the standards of both reverberation time and background noise level have been established for the appropriate aural environment in classrooms. In order to realize this, guidelines for architectural planning and interior finishing have been also suggested. However, in Korea, there has hardly been any guidelines for satisfying background noise criteria and investigation about sound insulation performance of current walls of classrooms. The present study investigates the structure of outer wall and walls between classrooms of two middle schools in order to analyze the sound insulation performance against both exterior and interior noises. Acoustic parameters including transmission loss, standardized sound level difference, and signal to noise ratio have been measured and analyzed for sound insulation performance of walls and flanking noises. As a result, concerning the walls in between classrooms, it was found that walls of dry construction have greater sound insulation performance rather than the walls of wet construction especially in mid and high frequency bands. Also, It was revealed that thermopane, insulated pair glass, of outer walls, has greater sound insulation performance than the double window consisted of two single pane glass. Regarding flanking noises, the standards were exceeded when all windows, or windows and doors front onto corridor were opened. It denotes that students could be disturbed with the sound transmission by the interior noises.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.326-331
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• 2011

Aluminum extruded panel used in a high speed train shows high stiffness, however, its sound insulation performance is remarkably decreased by local resonance phenomena. In this paper, improvement strategy of the sound insulation performance is proposed for the floor extruded panel used in HEMU-400x, 400km/h class next generation high speed train under development, and the improvement effect is verified by experiment. Aluminum extruded panel specimen for the floor is manufactured and urethane foam is installed in the core of the panel. Based on ASTM E2249-02, intensity transmission loss is measured and the improvement effect in local resonance frequency band is verified. Finally, improvement effect of the sound insulation performance is estimated on the layered floor structure including the foamed aluminum panel.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.116-118
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• 2014

A shape optimization problem is formulated to optimally design aluminum sandwich panel, which is used for high speed railway vehicle. An aluminum volume used in the panel is selected as a design objective with constraints on the stiffness and the transmission loss value. The formulated shape optimization problem is solved for a well -selected initial shape. The stiffness and transmission loss value of the obtained optimal shape are compared with those of the previously-reported panel.