• Title/Summary/Keyword: 자기소음

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A Study Interior Noise Reduction of a Maglev Train at Low Speed (저속 주행시 자기부상열차의 실내소음저감에 관한 연구)

  • 김현실;김재승;강현주;김봉기;김상렬
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.11 no.7
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    • pp.253-260
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    • 2001

  • A Study of interior noise reduction in the magelv train is presented. Tarin speed of interest is low such that aero-dynamic noise is negligible and power supply system is a dominant noise source. Based on the measurements of interior noise and acceleration levels during running and zero speed conditions, dominant noise sources are identified. After spectra characteristics of noise sources are investigated several noise reducing methods are studied such as STL increasement of floor panels. sealing. and absorption treatment It is found that the most important noise sources are VVVF inverter and SLM in running condition, whereas air conditioner and DC/DC converter are dominant in zero speed. Sine the major noise sources are under the floor complete sealing and high STL of the floor panel are shown to be the most crucial factors in noise reduction After sound absorbing material, which is polyurethan foam of 50 mm thickness, is thickness, is attached to the downward side of the floor in addition to sealing treatment, the interior noise is reduced by 3~4 dB.

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Noise Exposure of Radiographer Caused by Magnetic Resonance Imaging(MRI) (자기공명영상(MRI) 검사 시 방사선사의 소음노출)

  • Gil, Jong-Won
    • The Journal of the Korea Contents Association
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    • v.16 no.11
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    • pp.699-706
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    • 2016

  • This study aimed to propose the necessity and system establishment of noise reduction facility via evaluating noise level exposed by the radiographer due to MRI scan. Noise measurements were carried out using at S general hospital in Daejeon using 1.5 Tesla MRI (7 exams) and 3.0 Tesla MRI (16 exams), while using SC-804 noise meter. The measurement distance was from the soundproof door of the MRI room to the radiographer which measured 100cm, and the measurement height, the height to the radiographer's ears when working, 100cm. The noise measured for each exam was an average of three measures per exam which observed the noise occurring in each sequence recorded every 20 seconds. As the results, the maximum of noise exposed by the radiographer is 73.3 dB(A), which is MRCP by the 3.0 Tesla device, and also the maximum of average noise is 66.9(3.1) dB(A), which is Myelogram by the 3.0 Tesla device. Average noise by each device is 61.9(4.1) dB(A) by the 3.0 Tesla device and 52.0(3.1) dB(A) by the 1.5 Tesla device, which comes to the result that the 3.0 Tesla MRI device is about 10 dB(A) degree higher(p <0.001). The noise level exposed by the radiographer does not affect auditory acuity, but the level is able to incur a non auditory effect. The reflect sound can be removed by installing curtains in the rear wall of MRI control room in order to reduce the noises, but, first of all, An institutional system is needed in order to prevent noise.

  • https://doi.org/10.5392/JKCA.2016.16.11.699 인용 PDF KSCI