• 한국전자파학회지:전자파기술
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• 제12권1호
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• pp.34-41
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• 2001

Semiconductors performing digital clocking are a main source of radiated emission noise. Therefore, the most secure method of reducing emission noise is to reduce emission radiated from semiconductors; an application of an absorber to the surface of semiconductors is one of these methods, too. However, in reality, it is difficult to achieve as much effect of noise reduction as expected by using only absorber. It is confirmed by experiment in this paper that a loop area within chip has no correlation with radiated emission noise and it is clarified why the existing absorber fails to achieve a satisfactory effect of emission noise reduction. Besides, a new type of chip coating absorber has been developed which can cover up to semiconductor out lead by using ferrite coating material of ferrite/epoxy acrylate substance using only permeability loss out of electromagnetic wave reduction characteristics of materials. As a result of evaluating radiated emission noise by applying this coating absorber to semiconductor device, it could be confirmed that emission noise decreased from about 3 ㏈ up to 20㏈ depending on frequency.

• 한국소음진동공학회논문집
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• 제18권8호
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• pp.816-822
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• 2008

This study presents the design modification for SCR muffler of a commercial vehicle. Its main objective is the reduction of radiated noise at SCR muffler. For this study, the research of five steps were achieved by experimental and CAE analysis. First step is the measurement of radiated noise using impact-acoustic test. Second step is the source identification using experimental modal analysis. The cause of radiated noise source is confirmed by the resonance of end plates at SCR muffler. Third step confirms the possibility of resonance avoidance using SDM analysis applied the mass control. Fourth step is the suggestion of design modification which is the change of mode shape by CAE analysis. Last step is the verification of design modification using SYSNOISE analysis. Finally, the prototype product applied the countermeasure of resonance evasion was manufactured and the reduction of radiated noise at SCR muffler was confirmed by pass-by noise test.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 춘계학술대회 논문집
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• pp.483-484
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• 2010

Unit cabin means room, which is installed in the high value ship such as drill ship and FPSO, after pre-assembled. In order to develop the noise control design for a unit cabin, a variety of acoustic tests such as sound absorption, transmission, and radiated noise measurements were carried out by using the mock-up of living quarter. From the tests, it was found out that the combined noise level of a unit cabin could be dominated by the radiated noise from wall panel in low frequency range and the design guidelines for the noise control of unit cabin were fully established, such as the improvement of sound transmission loss between the cabin and corridor, and radiated cabin noise reduction.

• 소음진동
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• 제9권1호
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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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.488-489
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• 2014

This paper is a case study for the reduction of excavator Radiated noise. The main purpose of the study is to reduction noise for the cooling fan and hydraulic line which is main noise source of the excavator. Recent, noise regulations for the construction equipment is becoming stricter. Compare to past excavator drivers requirements for noise level demanding are becoming more and more. Therefore, this progress is an important role in determining the quality of the excavator.

• 소음진동
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• 제9권5호
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• pp.949-954
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• 1999

Speed-up and mass reduction of railway vehicle usually causes increased of the interior noise. One of the best ways to control the interior noise is to identify the noise level radiated from each of parts in the cabin. In this paper, we describe the method to estimate the interior noise nad evaluate the noise contribution to each of parts. This method is based that the sound pressure can be calculated by using the frequency response function and acceleration. According to analysis of the noise contribution, we validated that the noise radiated from the floor is the higher in the cabin. We also measured the noise distribution for the side and floor by using the microphone array in order to analyze the effect of the noise flowing into the cabin from the outdoors. Finally, we presented the plan of the interior noise reduction based on the noise levels radiated from each of parts.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.811-814
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• 2004

Radiated noise from high frequency transformers (HTFs) of switching mode power supply is mainly caused by the leakage inductance and the parasitic capacitance of HTFs. Generally, the radiated noise can be reduced by adding snubbers to switching power circuits or shielding HTFs. Radiated noise, however, is mainly affected by the shielding method. In this paper, the various shielding methods to reduce the radiated noise of EMI are analyzed, compared in the experimental studies. And it is proved that the radiated noise can be reduced according to the shielding methods of HFTs and the electrical connection between shields and power circuit.

• 한국소음진동공학회논문집
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• 제15권6호
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• pp.738-748
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• 2005

The ship radiated noise level fluctuates by the difference of interference and reverberation according to measurement methods and environmental conditions. These phenomena cause error of the source level estimation even in the same environment conditions. This paper describes a quantitative analysis and a reduction method for an error value to the source level estimation in spatial and temporal interference environment. The design criteria of the radiated noise measurement array composed of omni-directional hydrophones and the source level accuracy in the deep water range are given. The source level accuracy in the shallow water range is also derived based on the statistical model of the multiple reflection paths. The results are verified using the water tank experiment and the sea trial.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.431-434
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• 2005

Generally, noise in a reciprocating compressor is attributed to the driving force of a pump. However, close examination shows that the noise heard by customers finally results from radiation of a shell in a compressor, the noise caused by both transmission through a shell and resonance with the natural frequency of a shell. Therefore, the peak frequencies contributing to the overall level of a compressor' noise are closely concerned with vibration of a shell. That's why radiated noise by vibration can be reduced by changing the mode of a shell and by shifting the peak frequencies to other ranges, which are not globally related with the overall noise level. In this paper, the main peak frequencies are analyzed to reduce the radiated noise of a shell, and the vibration characteristics of a shell are examined through Frequency Response Function and Finite Element Analysis. Moreover, the Operational Deflection Shape for a shell is measured with consideration of real driving force of a pump. Finally, the optimum position on a shell, closely related to the main peak frequencies, is found, and the overall noise level caused by radiated noise of a shell is noticeably reduced by mass or stiffness modification of the position.

• 한국소음진동공학회논문집
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• 제21권12호
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• pp.1104-1111
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• 2011

This paper investigates the filtered velocity feedback(FVF) controller for the reduction of the acoustic power radiated from a clamped beam. The instability problem due to the non-collocated sensor/actuator configuration when using PZT actuator should be sorted out. The roll-off property of the FVF controller at high frequency helps to alleviate the instability. The dynamics of clamped beams under forces and moments pair and the FVF controller are first formulated. The formulation of the sound radiated power is followed. The open loop transfer function(OLTF) synthesized with 100 modes is used to determine the stability of the control system. The control performance is finally estimated. The levels of the vibration and the sound radiated power are reduced in the wide bandbelow the tuning mode of the FVF controller.