• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.372-376
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• 2014

This study is on acoustic radiation efficiency of a tiffened cylindrical model in water-multi-excitation with phase difference using commercial numerical program ABAQUS and SYSNOISE. When the stiffened cylindrical model is under multi-excitation with phase difference, the surface vibration field is variated with phase difference of excitation. By this different surface vibration field, the acoustic radiation efficiency is also variated with phase difference of excitation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.751-754
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• 2004

This paper presents a design of the directional radiation pattern by using the structural-acoustic interaction. For this purpose, prediction of the pressure distribution of the field points and radiation pattern of the structural-acoustic coupling system is shown. In order to get a strong coupling, coupled system that has a finite space and a semi-infinite space separated by two flexible walls and an opening is selected. A volume interaction can be occurred in structure boundary and a pressure interaction can be happened in the opening boundary. The coupled system is maximized the radiation power on the main axis and minimized the side lobe level.

• Journal of KSNVE
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• v.10 no.3
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• pp.444-450
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• 2000

Wheel-rail noise is normally classified into three catagories : rolling impact and squeal noise. In this paper rolling noise caused by the irregularity between a wheel and a rail is analysed as follows: The irregularity between the wheel and the rail is assumed as linear superposition of sinusoidal profiles. Wheel-rail contact stiffness is linearized by using Hertzian contact theory and then contact force between the wheel and the rail is calculated. vibration of the rail and the wheel is calculated theoretically by receptance method or FEM depending on the geometry of the wheel or the rail for the frequency range of 100-500 Hz important for noise generation. The radiation noise caused by those vibration response is computed by BEM To verify this analysis tools rolling noise is calculated by proposed analysis steps using typical roughness data and these results are compared with experimental rolling noise data. This analysis tools show reasonable results and finally used for the prediction of the Korean high speed train rolling noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.594-595
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• 2010

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.450-451
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• 2013

• Journal of KSNVE
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• v.8 no.1
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• pp.112-121
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• 1998

In this report, Experimental analysis for main factors and analyzing methods of electro-magnetic noise and no loading noise was conducted because of noise of AC generator, which is peripheral equipment by reduction of engine noise that would be the main cause of vehicle radiation noise. In addition, This is intended to suggest the noise reduction development basis of AC generator for actual fan and electro-magnetic noise by making-analyzing-testing it's sample.

• Journal of information and communication convergence engineering
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• v.9 no.5
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• pp.510-514
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• 2011

To detect the insulator in the fault state on the electric poles, we first measured radiation sounds from normal state insulators and error state insulators in the anechoic chamber. We processed the signals in frequency domain to find the features with filter bank, narrow band and wide band analysis. So we could found two apparent results from their frequency spectrums - one was 120Hz harmonic components, the other was high average noise level than normal state ones. Then we also introduced a technique for the direction detection of the fault state insulator using the cross correlation from the three dimensional array microphones. To eliminate the noise signal from unexpected directions, we suggested the zero padding technique in cross correlation function. From these, we could conclude that acoustic fault detection techniques are useful of the detection of insulators' faults and the estimation of the direction of the fault state insulators.

• Journal of the Korean Society of Radiology
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• v.15 no.7
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• pp.1065-1072
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• 2021

In Computed Tomography, abdominal examination showed the highest proportion of use, and effort of reducing the radiation dose is required. Recently introduced Iterative Reconstruction(IR) is repetitive reconstruction technique of Computed Tomography. SIEMENS' IR, ADMIRE and GE's IR, ASIR-V, were used in this examination. Noise, % Contrast, and High contrast resolution were measured by using ACR phantom for image quality evaluation. In addition, CTDI_vol and DLP displayed in the CT device were used for dose evaluation. When FBP and IR were compared, stage 2 to stage 5 of ADMIRE and 10, 30, 50, 70, and 90% of ASIR-V were applied, noise could be reduced from a minimum of 0.46 to a maximum of 2.38 in ADMIRE compared to FBP, and noise from a minimum of 0.51 to a maximum of 2.5 in ASIR-V compared to FBP. Also, % Contrast and High contrast resolution of FBP and IR were no statistical difference. When IR was used for abdominal CT examination, the radiation dose of ADMIRE is reduced by 25.39% compared to the radiation dose of FBP. Also, the radiation dose of ASIR-V is reduced by 16.61% compared to the radiation dose of FBP. In conclusion, it is believed that if IR is applied during abdominal CT examination, the radiation dose can be reduced without deteriorating the image quality.

• Journal of KSNVE
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• v.8 no.5
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• pp.887-899
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• 1998

It has been resulted that Lagrange multiplier method with statistical approach was superior to traditional harmonic balance method in identifying the nonlinear loudspeaker parameters when output signals were contaminated with Gaussian random noise. We have known that the displacement-dependent characteristic values of nonlinear parameters identified by traditional harmonic balance method were estimated less than original values by the increase of output noise and the stiffness coefficients were very sensitive to output noise. Also, by the sensitivity analysis we have verified that the harmonic distortions in acoustic radiation was mainly due to nonlinearity of force factor caused by uneven magnetic fields and that reducing the nonlinearity of damping coefficients were very effective for improving second harmonic distrotion of acoustic radiation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.2
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• pp.151-154
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• 2020

Radiation noise due to EMI noise generated by the driving circuits of LED lighting devices in a medical imaging room was reduced by decreasing the noise source in the driving circuits and changing the number of corrections in EMI filters. Noise attenuation and filter changes enabled driving circuits that reduced the electromagnetic waves. Such circuits were efficiently designed by using capacitors and inverters in a given space. Therefore, the malfunction of radiation devices can be minimized by using EMI-reduction filter circuits, and reliable operation of medical devices can be expected by blocking electromagnetic waves.