• Proceedings of the KSR Conference
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• 2011.10a
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• pp.663-669
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• 2011

Since railway vehicle's improvements on speed and weight has caused interior noise, the passenger's convenience fell dramatically. Therefore many on-going researches are dedicated to reduce interior noise. In this study the analytical prediction of interior noise reduction has done through filling up the empty space using form and to modify the floor structure, which contributes highly with interior noises. Using Statistical Energy Analysis(SEA), the interior noise of the vehicles without the form filling on the floor structure and the vehicles with form filling and also a modified structure has been predicted. The selected percentage of form filling was 0, 50, 100% and through this research the analysis of noise reduction by form filling has been made. When floor structure has been filled with form, approximately 2 dB of noise reduction was observed and the difference of noise reduction level with 50 and 100% form filling was predicted to be very little. Through this study, the expectation of interior noise reduction in high speed trains is considered high.

• Journal of Environmental Science International
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• v.24 no.5
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• pp.647-655
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• 2015

In this study, to targeting Songpa of Seoul, were analyzed the effect on the noise mitigation in roadside buffer green spaces. Noise of Songpa Street buffer green space was determined to be higher during the day than at night. In addition, it was most of 60 db or more. However, the noise reduction function of the buffer green was not greatly affected by time. In the case of noise reduction rate, during the day time it was the order of the mounding type (18.14%)> plain type (5.73%)> slope type (4.08%), And, in the case of night time, it was the order of the mounding type (11.29%)> slope type (10.22%)> plain type (4.42%). Noise reduction rate, all of the daytime, was the highest in the mounding type. As a result of the factors on the amount of reduction of noise, More physical structure is mounding type, green structure is the stratification of green space, and the number of individuals is large, the higher the tree planting density, it is determined that the noise reduction effect is high. Also, factors affecting the noise reduction effect of the day and night were different.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.1143-1151
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• 2013

Reasonable methods are needed to predict the noise level of new/existing roads and to select means of noise reduction. In this study, the noise reduction effects of both soundproof walls and quiet pavements were predicted. The noise reduction effects of quiet pavements were predicted by measurement data obtained using the CPX method in test pavements. The noise reduction effect was predicted by KHTN program when applied to soundproof walls and quiet pavement. As a result, the predicted noise level was similar to the measured one. The design method was suggested by an economic analysis using noise benefit of predicted noise reduction. The research suggests that the optimum alternative has to be determined using noise prediction method and life-cycle cost analysis.

• Journal of KSNVE
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• v.9 no.1
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• pp.189-195
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• 1999

The noise radiated by the rotary compressor for a room air-conditioner was investigated experimentally. Noise characteristics and structural eigen modes of the compressor were identified through sound tests and modal tests each other. From these tests. we found that the accumulator has a big contribution to the noise radiation. So, various structural modifications for the accumulator were performed and these modification methods were found efficient to the noise reduction from verification tests.

• Proceedings of the KSR Conference
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• 1999.05a
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• pp.218-225
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• 1999

Speed-up and mass reduction of EMU(Electrical multiple unit) causes increase of interior noise. One of the best ways to reduce the interior noise is to identify noise sources. In this study, we evaluated interior noise by contribution analysis. This method is to predict the interior noise contribution of carbody by using transfer function between acceleration and sound pressure. The plan of the interior noise reduction based on the test results was also presented.

• MALSORI
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• no.64
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• pp.105-119
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• 2007

Noise reduction technologies are indispensable to achieve acceptable speech quality in VoIP systems. This paper proposes a Wiener filter optimized to the estimated SNR of noisy speech for the noise reduction in VoIP environments. The proposed noise canceller is applied as a pre-processor before speech encoding. The performance of the proposed method is evaluated by the PESQ in various noisy conditions. In this paper, the proposed algorithm is applied to G.711, G.723.1, and G.729A which are all VoIP speech codecs. The PESQ results show that the performance of our proposed noise reduction scheme outperforms those of the noise suppression in the IS-127 EVRC and the ETSI standard for the advanced distributed speech recognition front-end.

• MALSORI
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• no.48
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• pp.155-173
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• 2003

This paper proposes a noise reduction-based speech detection method under telephone channel environments. We adopt the AURORA front-end noise reduction algorithm based on the two-stage mel-warped Wiener filter approach as a preprocessor for the frequency domain speech detector. The speech detector utilizes mel filter-bank based useful band energies as its feature parameters. The preprocessor firstly removes the adverse noise components on the incoming noisy speech signals and the speech detector at the next stage detects proper speech regions for the noise-reduced speech signals. Experimental results show that the proposed noise reduction-based speech detection method is very effective in improving not only the performance of the speech detector but also that of the subsequent speech recognizer.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.1
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• pp.71-76
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• 2009

In a running blower, there are various exciting forces which can generate noise. The noise of an running industrial fan or blower depends on the structure of a fan, the machining accuracy of each element, and assembled conditions. Many studies have been carried out to reduce the noise of it. In this study, 3-hole buffs are used in pipe of blower to study the influence the number and position of buffs on the noise reduction at inlet and outlet in pipe. Commercial engineering software ANSYS and SYSNOISE were employed to analyze the characteristics and reduction ratio of pressure. It is concluded that optimal position and number of buffs in pipe of blower to show the least reduction ratio of pressure.

• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.494-499
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• 2005

This paper introduces a study for the noise reduction of a range hood for household. Generally, range hoods have a built-in sirocco fan from which harsh noises are generated. Though the harsh noises have low noise level, these kinds of noises make most of the users nervous. For the purpose of noise reduction, in this study, a perforated plate system is installed in the fan housing of range hood. From the experimental results, it is confirmed that the noise level emitted from the range hood was decreased more than 10dB(A) in all 1/3 octave bands due to the effect of noise reduction by perforated plate systems.

• Journal of the Korean Society of Visualization
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• v.21 no.3
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• pp.39-48
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• 2023

In this study, we investigate the effects of slots installed on the tip of a rotor blade on aerodynamic characteristics. The slots weaken the strength and spatial coherence of the tip vortex at early vortex age and accelerate the dissipation of the generated tip vortex. Accordingly, the turbulence intensity of the rotor wake is reduced at both near and far wake, which leads to a reduction in broadband noise. Tonal noise is also reduced by mitigation of tip vortices, but tonal noise reduction is limited to a narrower range of azimuths than broadband noise due to the extinction of tip vortices. In addition, slots reduce both mean thrust and thrust fluctuations. Reduction in thrust fluctuations leads to a reduction in blade loading noise, resulting in a reduction in tonal noise.