• Title/Summary/Keyword: radiation noise

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A Study on Noise Radiation of Compressor Shell (압축기 쉘의 방사소음에 관한 연구)

  • Chae, Seung-Hoon;Hwang, Won-Gul;Oh, Il-Kwon;Park, Sung-Woo;Ryu, Ki-O
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.11a
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    • pp.164-167
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    • 2005
  • The noise level of refrigerating units is becoming more important to the manufacturer and the user of the product. Invariably, the compressor is a significant contributor to the overall noise level. Especially a major portion of the noise radiated by the vibration of the compressor shell. This paper presents an approach to relate the dynamic characteristics of the compressor shell with the noise radiation properties and the methods of redesigning the compressor shell to reduce the noise radiation. To relate the dynamic characteristics of the compressor shell with the noise radiation properties, the vibration and radiated sound were measured with the running compressor. Based on the results of these tests correlations between the shell vibration characteristics and the noise radiation properties are identified It was found that the vibration on the compressor shell and the noise radiated from the compressor were stronglycorrelatedincertainfrequencybands.

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A New Extraction Method for the Radiation Efficiency and Radiation Directional Coefficient (방사효율과 방사방향 계수에 대한 새로운 산출기법 연구)

  • Jung, Woo-Jin;Lee, Jong-Ju;Kang, Myung-Hwan;Jeon, Jae-Jin
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.2
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    • pp.93-101
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    • 2014
  • Underwater radiated noise is the key in acoustic stealth performance of modern naval ships. The underwater radiated noise predicted by the hull vibration with radiation efficiency cannot always give the information of radiation pattern which is essential to analyze of detection probability by enemy and to improve the operational performance of the naval ship. The radiation pattern of underwater radiated noise is able to be obtained with radiation efficiency and radiation directional coefficient. In this paper, a new method to extract the radiation efficiency and radiation directional coefficient is suggested and proved with the simulation and experiment by using cylindrical shell of 70 cm diameter in air.

A Study on the method for the extraction of the radiation efficiency and radiation direction coefficient (방사효율과 방사방향 계수 산출기법 연구)

  • Jung, Woo-Jin;Kang, Myung-hwan;Lee, Jong-Ju;Jeon, Jae-Jin
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2013.10a
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    • pp.738-743
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    • 2013
  • Underwater radiated noise is the key in acoustic stealth performance of modern naval ships. The underwater radiated noise predicted by the hull vibration with radiation efficiency cannot give the information of radiation pattern which is essential to the analysis of detection possibility by enemy and to improve the operational performance of the naval ship. The radiation pattern of underwater radiated noise is able to be obtained with radiation efficiency and radiation direction coefficient. In this paper, a new method to extraction the radiation efficiency and radiation direction coefficient is suggested and proved with the simulation and experiment by using cylindrical shell of 70cm diameter in air.

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Study on the Sound Radiaton Characteristics of Trains by Sound Intensity Method (음향 인텐시티법을 이용한 주행열차의 음향방사특성의 검토)

  • 주진수;김재철
    • Journal of KSNVE
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    • v.8 no.4
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    • pp.603-608
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    • 1998
  • In order to obtain basic data for the prediction of railway noise propagation, the noise radiation characteristics (source position, radiation directivity, etc) of trains were measured by using the sound intensity method. The measurements were performed at a side of railway by setting an intensity-probe array. As the measurement results, it was found that rolling noise due to interaction between wheel and rail and motor noise radiation from the lower part of train are dominant. The location of main sound sources can be described as being at the height of 0.1m in the center line of track, and the radiation directivity in the cross section of actually running trains are presented as a dipole source.

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A Noise Re-radiation Calibration Technique in Interferometric Synthetic Aperture Radiometer for Sub-Y-type Array at Ka-Band

  • Seo Seungwon;Kim Sunghyun;Choi Junho;Park Hyuk;Lee Hojin;Kim Yonghoon;Kang Gumsil
    • Proceedings of the KSRS Conference
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    • 2004.10a
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    • pp.577-580
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    • 2004
  • To overcome with large size noise source distribution network design difficulty in interferometric radiometer system, especially for sub-Y-type array, a new on-board calibration technique using noise re-radiation is proposed in this paper. The suggested calibration technique is using noise re-radiation effect of center antenna after noise source injection from matched load. This approach is especially proper to sub-Y-type array interferometric synthetic aperture radiometer in mm-wave frequency band. Compared with noise injection network of a conventional synthetic aperture radiometer, the system mass, volume, and hardware complexity is reduced and cost-effective. Only one internal noise source, matched load, is used for injection using noise re-radiation technique a small set of sub-Y receiver channels is calibrated. Detailed calibration scenario is discussed and simulation results about noise re­radiation effect are presented.

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Asymmetric Directionality of Broadband Ship Radiation Noise at Bow-Stern Aspect (광대역 선박방사소음의 선수-선미 비대칭 방향성)

  • Lee, Keunhwa;Kim, Minkyu;Seong, Woojae
    • The Journal of the Acoustical Society of Korea
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    • v.34 no.5
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    • pp.343-350
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    • 2015
  • In this paper, we perform a study on the directionality of broadband ship radiation noise, mainly resulting from propeller cavitation. By examining a few foreign studies for ship radiation noise and domestic data measured in Korean waters, it is reconfirmed that the asymmetric directionality of the ship radiation noise at bow and stern aspect is observed commonly. In order to explore the reason of this asymmetric directionality, a numerical analysis, based on the acoustic boundary element method, is applied into the geometric form equal to the commercial ship used in the domestic experiment. The numerical result demonstrates that the diffraction of the propeller cavitation noise by ship is a primary cause of the bow-stern asymmetry in the directionality of ship radiation noise.

A Study on Radiation Characteristics of Noise Sources for Korean Train Express (한국형 고속철도의 소음 방사특성에 관한 연구)

  • Kim, Jae-Chul;Koo, Dong-Heo;Moon, Kyeong-Ho;Lee, Jae-Eung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11b
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    • pp.323-327
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    • 2002
  • In order to control the railway noise, the radiation characteristic of the noise during the train passage should be analyzed. Generally, the major noise sources for Korean Train Express are the rolling noise and power unit noise up to 300km/h. In this paper, we describe on a train model that is considered to be a row of point sources to calculate the radiation characteristic. The calculation results are compared with short distance measurement. It is shown that the radiation characteristic of the rolling noise is dipole type. The noise generated by the power unit is radiated as the cosine type. The noise level at an observer is increased in the direction of motion and reduced in the direction opposite to the motion with increasing of the train speed. The calculation results including the moving effect of the noise source at 300km/h show in good agreement.

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Experimental Analysis of Wheel Radiation Noise of HANVIT 200 Train in Curve Lines (곡선부에서의 한빛 200 열차 차륜방사 소음 특성)

  • Lee, Chan-Woo;Kim, Jae-Chul
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.907-910
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    • 2008
  • The wheel radiation noise characteristic of Korean tilting train(Hanvit 200) on curved rail under the field test conditions is analyzed in this paper. The test railroad track was selected from Seodaejon to Songjeongri in Honam line. $5^{th}$ and $6^{th}$ car are decided to measure radiation noise level among a train of six cars. The test subject curve radius executed from R400, R500, R600, R700 and R800 segments. The speed of test trains when from R600 and R800 curves existing operation speed and speed up 20% of existing speed. On curved rail at the time of operation speed of Hanvit 200 trains from below 95km/h wheel radiation noise level at $94dBA{\sim}99dBA$, the operation speed from between $100km/h{\sim}144km/h$ wheel radiation noise level at $100dBA{\sim}106dBA$.

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Measurement of Acoustic Radiation Efficiency of the Submerged Circular Cylindrical Structure in Water Tank (수조에서의 원통형 구조물 음향방사효율 측정에 관한 연구)

  • Han, Seungjin;Kang, Myunghwan;Lee, Jongju
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.25 no.11
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    • pp.747-752
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    • 2015
  • Underwater radiated noise is an important characteristic in the naval weapon systems. It is difficult to measure the radiation efficiency of underwater vehicle, such as UUV(unmanned underwater vehicle) and underwater weapons in real operation environment. In this study, acoustic radiation efficiency of a circular cylindrical structure is measured in the laboratory-water tank. The radiation efficiency is compared with the numerical results and it is found that they are in a good agreement. Therefore, the measurement method can be applied effectively for predicting the underwater radiation noise and effectiveness of radiation reduction means.

A Study on Radiation Characteristic for Railway Noise (철도소음의 방사특성에 관한 연구)

  • Kim, Jae-Chul;Moon, Kyeong-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.4
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    • pp.531-536
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    • 2003
  • In order to control the railway noise. we should know the radiation characteristic of the noise during the train passage Generally, the railway noise sources for conventional trains are classified by the rolling noise and power unit noise in tangent track. In this Paper. we describe on a train model that is considered to be a row of point sources to calculate the radiation characteristic The calculation results are compared with short distance measurement of three kinds of trains (EMU, Mookungwha, Saemaul). It is shown that the radiation characteristic of the rolling noise that is major noise source of electric multiple unit is dipole type. We know that characteristic of the engine noise is radiated as the cosine type.