• 한국소음진동공학회논문집
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• 제19권1호
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• pp.24-34
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• 2009

This paper investigates active noise control of ducts using filtered-x least mean square(FXLMS) algorithms to reduce noise transmission. Single channel FXLMS(SFXLSM) and multiple channel FXLMS(MFXLMS) algorithms are used to implement the active control systems. The transmission loss is significantly increased by SFXLMS but the sound pressure level(SPL) at the upstream of the error sensor is increased while that of downstream is very low. This increase of the upstream SPL causes the duct wall to vibrate and so to radiate noise. To prevent the wall vibration generated by the sound field upstream, global sound field control is required. To reduce SPL globally along the duct, active noise control using MFXLMS is implemented. We can then be obtained globally reduced SPL. It is found experimentally that the vibration level, and so the radiated noise level, can be reduced by the active noise control using MFXLMS.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1441-1447
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• 2008

This research studies the effects of community noise around railway, noise from the inside/outside noise of the High-Speed EMU. First study part of this year is research of the noise source. The modeling methodology for prediction of noise level including the frequency property, velocity dependence, sound pressure of noise source is investigate. Second part is research on the sound transmission loss. An exclusive program which could analyze the sound transmission loss of the floor, the sides(mirror), insulator in High-Speed EMU has to be developed. Third part is research on the train inside/outside and Prediction for community Noise. In order to predict the noise when the High-Speed EMU is traveling at the outside and along tunnels, the result of the research can be derived by evaluating the effect of the noise on the upper/middle parts of the carriage and on the railroad way round about with using the program.

• International Journal of Advanced Culture Technology
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• 제7권2호
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• pp.218-226
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• 2019

In modern society, people live in an environment with artificial or natural noise. Especially, the sound that corresponds to the artificial noise makes the noise itself and affects each other because many people live and work in the city. Sounds are generated by the activities and causes of various people, such as construction sites, aircraft, production machinery, or road traffic. These sounds are essential elements in human life and are recognized and judged by human auditory organs. Noise is a sound that you do not want to hear by subjective evaluation, and it is a loud sound that gives hearing damage or a sound that causes physical and mental harm. In this study, we introduce the method of stimulating the human hearing by finger vibration and explain the advantages of the proposed method in various kinds of a noise environment. And how to improve the sound quality to improve efficiency. In this paper, we propose a method to prevent the loss of hearing loss and the transmission of sound information based on proper signal to noise ratio when using portable IT equipment in various noise environments.

• 한국기계가공학회지
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• 제11권3호
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• pp.116-121
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• 2012

In recent years, world is faced with a transportation energy dilemma, and the transportation is dependent on a single fuel - petroleum. However, Hybrid Electric Vehicle(HEV) technology holds more advantages to reduce the demand for petroleum in the transportation by efficiency improvements of petroleum consumption. Therefore, there is a trend that lower gear noise levels are demanded in HEV for drivers to avoid annoyance and fatigue during operation. And meshing transmission error(T.E.) is the excitation that leads to the tonal noise known as gear whine, and radiated gear whine is also the dominant source of noise in the whole gearbox. This paper presents a method for the analysis of gear tooth profile and lead modification, and the predictions of transmission error and load distribution are shown under one loaded torque for the 1st gear pair of HEV gearbox. The test is also obtained before tooth micro-modification under the torque. At last, the appropriate tooth modification is used to minimize the transmission error and load distribution under the loaded torque. It is a good approach which the simulated result is used to improve the design in order to minimize the radiation gear whine noise.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권2호
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• pp.117-126
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• 1999

The environmental impact of the KEPCO 765-kV transmission line was studied using a full scale test line in order to develop the design technology. Therefore this paper describes an environmental design summary of the audible noise, hum noise, wind noise, radio interference, TV interference and electric field measurement from the KEPRI 765-kV double circuit transmission test line with a bundle of $6-480mm^2$ conductors per phase. The analysis of the test results shows that 6-Rail and 6-Cardinal conductors bundle satisfy the audible noise criterion & TV interference under the stable rainy weather condition and the radio interference level under the fair weather. And the other items are also agreed with the design level criterion for KEPCO 765-kV transmission line.

• 대한전기학회논문지:전력기술부문A
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• 제49권1호
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• pp.37-42
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• 2000

The radio noise produced by corona discharge in high voltage transmission lines is one of the most important line design considerations. Therefore it is necessary for transmission line designers to pre-evaluate radio noise using prediction formulas or field test results. In this paper, more accurate and useful formulas for predicting radio noise during fair and foul weathers in high voltage AC transmission lines were proposed through comparison with the existing formulas. Also it was verified by comparing with the long-term measured data from operating lines that the proposed formulas are more accurate. The proposed prediction formulas are developed by the applications of nonlinear least squares optimization method to radio noise database collected from lines throughout the world.

• 한국소음진동공학회논문집
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• 제26권4호
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• pp.420-427
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• 2016

Diverse research on gearing systems have been made to resolve gear NVH problems for many decades, and transmission error (T.E.) has been identified as one of the main sources generating gear noises. While gear profiles and amounts of tooth modifications have influences on gear noise in the design aspect, it is found that bad manufacturing conditions such as burrs, bumps and damage, which result in improper gear operating conditions, produce gear noise with respect to manufacturing process. In this paper, T.E. measurement system was introduced to examine the gears damaged or improperly manufactured, while they are assembled, by comparing T.E. values and various gear conditions with theoretical ones. This T.E. measurement system, following grinding machining process, has been installed in a manufacturing line in 2014, and it results that the transmission rework to resolve manufacturing problems is not needed at the end of line.

• 한국정보통신학회논문지
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• 제16권1호
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• pp.20-25
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• 2012

천리안 위성은 해양 관측과 기상영상 전송, 그리고 Ka 대역 위성통신 신호 중계를 위한 다목적 복합위성으로 2010년 발사되어 운용되고 있다. Ka 대역 위성통신 중계기는 MSM 스위치 기능으로 다중 빔 지향이 가능하고 다중모드 고속 데이터를 전송할 수 있다. 천리안 위성통신 중계기는 MSM 기능으로 다수의 신호발생기와 Ka 대역의 주파수 사용으로 시스템 위상잡음이 증가할 수 있다. 위상잡음은 다중모드 및 고속 데이터 전송에 영향을 미치고 있으며, 높은 위상잡음을 갖는 위성 전송시스템은 전송 신호를 복원하기가 어렵다. 본 논문에서는 천리안 위성통신중계기의 위상잡음을 측정하고, 측정된 위상잡음을 수신 잡음대역폭 관점에서 위상잡음 영향을 분석하고 평가한다. 아울러, 천리안 위성통신 중계기 위상잡음에 대한 다중모드 및 고속 전송 데이터의 전송 성능을 평가한다.

• 한국정보통신학회논문지
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• 제20권10호
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• pp.1831-1836
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• 2016

본 논문에서는 차세대 위성통신 규격인 DVB-RCS2 기반 VSAT 단말 시스템의 송수신부 위상잡음 스펙트럼 분포 특성을 분석한다. VSAT 순방향 링크는 DVB-S2 ACM 기반 APSK 고차 전송모드를 사용하며, 역방향 링크는 DVB-RCS2 기반 PSK 및 QAM 계열의 고차 전송 모드를 사용한다. 고차 전송 모드를 사용함에 따라 위상잡음에 의한 영향이 나타나며, 위성전송시스템 신호발생부의 위상잡음 특성에 따라 전송 성능의 열화가 지배적으로 나타난다. 위성전송 환경에 따라 가변적으로 전송 데이터 율와 전송 모드를 가변하는 전송방식을 고려하여 요구 위상잡음 특성을 분석하고 차세대 VSAT 전송 파라미터를 수용하는 전송시스템 신호발생부의 위상잡음 특성을 제시한다.

• 한국소음진동공학회논문집
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• 제20권8호
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• pp.703-709
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• 2010

An analysis tool for predicting transmission loss in high speed trains based on combined use of the statistical energy analysis and the finite element methods has been proposed. The analysis utilizes a commercially available numerical solver VA ONE with imbedded NASTRAN module. The proposed analysis tool is first verified by comparing numerically predicted transmission loss of a light rail transport(LRT) structure with experimental results. The comparison shows that the numerically predicted transmission loss is similar to the experimental data. The analysis tool is then applied to the prediction of transmission loss in the high speed train(HST) currently under development. Various sub-structures such as the floor, side panel and ceiling have been numerically analyzed to predict their transmission losses. The results obtained here can be used as input data for predicting the interior noise level of the HST at design stage.