• Journal of The Korean Astronomical Society
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• v.50 no.1
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• pp.7-20
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• 2017

We carry out the study of $850{\mu}m$ sources in a part of the XMM-LSS field. The $850{\mu}m$ imaging data were obtained by the SCUBA-2 on the James Clerk Maxwell Telescope (JCMT) for three days in July 2015 with an integration time of 6.1 hours, covering a circular area with a radius of 15'. We choose the central area up to a radius of 9'.15 for the study, where the noise distribution is relatively uniform. The root mean square (rms) noise at the center is 2.7 mJy. We identify 17 sources with S/N > 3.5. Differential number count is estimated in flux range between 3.5 and 9.0 mJy after applying various corrections derived by imaging simulations, which is consistent with previous studies. For detailed study on the individual sources, we select three sources with more reliable measurements (S/N > 4.5), and construct their spectral energy distributions (SEDs) from optical to far-infrared band. Redshift distribution of the sources ranges from 0.36 to 3.28, and their physical parameters are extracted using MAGPHYS model, which yield infrared luminosity $L_{IR}=10^{11.3}-10^{13.4}L_{\odot}$, star formation rate $SFR=10^{1.3}-10^{3.2}M_{\odot}yr^{-1}$ and dust temperature $T_D=30-53K$. We investigate the correlation between $L_{IR}$ and $T_D$, which appears to be consistent with previous studies.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.2
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• pp.197-205
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• 2017

We investigate the slat noise generation mechanism by using large-eddy simulation (LES) and simple source modeling based on linearized Euler equations. An incompressible LES of an MD 30P30N three-element airfoil in the high-lift configuration is conducted at $Re_c=1.7{\times}10^6$. Using the total derivative of the hydrodynamic pressure (DP/Dt) acquired from the incompressible LES, representative noise sources in the slat cove region are characterized in terms of simple sources such as frequency-specific monopoles and dipoles. Acoustic radiation around the 30P30N multi-element airfoil is effectively computed using the Brinkman penalization method incorporated with the linearized Euler equation. The directivity pattern of $p^{\prime}_{rms}$ at $r=20c_{slat}$ in the multiple sources is closely compared to that obtained by the application of the LES/Ffowcs-Williams and Hawking's methods to the entire flow field. The power spectrum of p' at ${\theta}=290^{\circ}$ is in good agreement with the data reported in BANC-III, especially the broadband part of the spectrum with a decaying slope ${\propto}f^{-3}$.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.11
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• pp.1037-1042
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• 2007

KTX trains show a high interior noise level in tunnel with concreted track at 300 km/h. Generally, the concreted track has higher sound emissions compared with ballasted track due to the reduced absorption and the major sources of interior noise for KTX are known as the aerodynamic noise and rolling noise. Therefore, It is necessary to find out noise source and noise components to affect interior noise in tunnel with concreted track. In this study, we measure the noise and vibration inside KTX in tunnel in order to find the cause of the interior noise of KTX. The analysis results show that the interior noise of KTX in tunnel with concreted track is increased sharply by a low frequency below 80 Hz. We know that the low frequency noise inside KTX in tunnel with concreted track is generated at the natural frequency of carbody by aerodynamic noise outside gangway and rolling noise. In order to reduce the noise level at 80 Hz, modification of mud-flap length between carbodys is suggested and the effect of noise reduction is examined in tunnel with concreted track.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1793-1801
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• 2016

Speech enhancement is a challenging problem due to the diversity of noise sources and their effects in different applications. The goal of speech enhancement is to improve the quality and intelligibility of speech by reducing noise. Many research works in speech enhancement have been accomplished in English and other European Languages. There has been limited or no such works or efforts in the past in the context of Tamil speech enhancement in the literature. The aim of the proposed method is to reduce the background noise present in the Tamil speech signal by using wavelets. New modified thresholding function is introduced. The proposed method is evaluated on several speakers and under various noise conditions including White Gaussian noise, Babble noise and Car noise. The Signal to Noise Ratio (SNR), Mean Square Error (MSE) and Mean Opinion Score (MOS) results show that the proposed thresholding function improves the speech enhancement compared to the conventional hard and soft thresholding methods.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.11
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• pp.838-844
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• 2003

The noise and vibration reduction schemes of an industrial robot are studied. Experimental procedures are employed to examine the sources of robot noise. A parametric study is undertaken to observe the effects of each part such as gear, shaft and housing on the sound pressure level. After the part which mainly effects on the noise is proved, we propose countermeasures for reducing the noise and vibration of the robot system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.636-640
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• 2006

In this study, metrics for evaluation of heavy-weight impact noise were investigated. Heavy-weight impact noises generated by impact ball were recorded in real apartments using binaural microphone. Those sounds were classified into three groups according to frequency characteristics in order to control aspects which affect subjective responses to heavy-weight impact noise. Sound sources for auditory experiment were selected based on the classification result. Then auditory experiments were conducted to investigate the relationship between level indices and subjective responses. The results showed that $L_{Aeq},\;L_{Amax}$ and $LL_z$ as well as $L_{iFmax,AW}$ were highly correlated with subjective response. Therefore, $L_{Aeq}$ and $L_{Amax}$ can be used as metrics for evaluation of heavy-weight impact noise. In further studies, it is needed to verify classification of heavy-weight impact noise generated by bang machine and impact ball.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.1-4
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• 2008

Prediction models currently being used for road traffic noise in apartment are equation of NIER, HW-NOISE of Korea Expressway Corporation, FHWA of United States, CRTN of United Kingdom, NMPB of France, ASJ RTN-Model 2003 of Japan and ISO 9613-1, 2 as a international standard. ISO 9613 species an engineering method for calculating the attenuation of sound during propagation outdoors in order to predict the levels of environmental noise at a distance from a variety of sources. This study, prior to investigation of every prediction methods listed above, aims to examine the model internationally standardized and to establish a reference for the prediction of road traffic noise in apartment.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.2
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• pp.324-330
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• 2013

The dispersion of acoustic noise during the turn-on and turn-off switching of HEV(hybrid electric vehicle) relay was experimentally analyzed to identify the reason for the dispersion of noise level. An effective method was proposed to reduce the dispersion of noise level. First, a method to wrap the side of moving core with a tape was adopted to reduce the transverse vibration. It enabled the moving core to make a consistent motion and reduce the dispersion of noise level from switching operation of relay. Second, the dispersion of noise level from vibration transmission of parts such as the outer frame and yoke caulking part of relay were tested to find out main sources. From this result, it was identified that the yoke caulking part made inconsistent transient vibration and noise dispersion.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.339.1-339
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• 2002

Noise of the VVVF inverter and DC/DC converter, which are the most dominant noise sources of maglev train at low speed, is studied. The coils inside inverter and converter are excited by the electro-magnetic forces, which results in core vibration and generations of the noise. It is found that the spectra of the noise show many harmonics, where there exist several different fundamental frequencies. (omitted)

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1026-1032
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• 2010

In this paper, To estimate the train exterior noise and environment noise which are occur when High-Speed EMU is driving with the speed of 370km/h, Estimated sound source about noise that is appeared during operation based upon noise SPL values. Based on aero-dynamic noise source and wheel-rail noise source, these were already used to the existed research, we have estimated each sound power about measured noise, and computed the sound source to apply on the High-Speed EMU, and also calculated the sound power in case of the maximum operation speed of 370km/h.