• The Journal of the Acoustical Society of Korea
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• v.20 no.7
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• pp.13-20
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• 2001

The active noise cancellation system offers a better low frequency performance with a smaller and lighter system compared to a passive one. This paper presents an active noise control system capable of reducing the noise in a helmet after attenuating the external noise using the helmet as the passive noise reduction system, which consists of a controller for inverting and compensating the phase delay, a microphone for picking up the external noise, and a loudspeaker for radiating the acoustic anti-phase signal to reduce the external noise. In this paper, external noise can be reduced by noise controller by compensating the phase difference to be 180°in the frequency of maximun value in the amplitude response. The noise of the phase delay covered from 50°to 310°was reduced in this system and it is possible to obtain a noise reduction of up to approximately 20 dB at the ears in the enclosure.

• Proceedings of the KAIS Fall Conference
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• 2012.05b
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• pp.778-780
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• 2012

국내 전동차에는 슬라이딩 도어가 널리 사용되고 있으나 노이즈에 취약한 단점이 있었다. 저속 운행시에는 외부로부터 유입되는 소음이 문제가 되지 않았으나, 전동차가 고속으로 운행되면서 소음이 큰 이슈로 자리 잡게 되었다. 전동차 소음의 주요 요인은 도어시스템에서 외부로부터 유입되는 공기를 완전히 차단하지 못해서 발생하게 된다. 플러그 도어시스템은 구조상 노이즈 문제에 강한 특성을 가지고 있다. 그러나 현재 플러그 도어는 국산화가 이루어져 있지 않아 국산화를 위해 전기식 플러그 도어를 개발하여 시험을 진행 중에 있다. 본 논문에서는 개발한 전기식 플러그 도어시스템의 개발 내용 및 구성에 대해 다루고자 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.259-264
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• 2001

It is necessary to predict the sound pressure level(SPL) in rooms before designing an apartment when exterior noises are produced. In order to predict SPL for an apartment that has some specific exterior noises, the following should be known: the characteristics of outdoor noise, sound insulation performance and sound level differences of each room. The purpose of this study is to find out the possibility of predicting sound pressure level of rooms in an apartment by analysing sound level differences among rooms. Sound sources used in this experiment are construction noise, aircraft noise, railroad noise, road traffic noise and white noise as a reference to compare with the previous four. These noises were recorded and reproduced by speaker. As a result, we found that within the sound reduction pattern, the sound difference level appeared uniform depending on the sound insulation characteristics of the windows installed when facing the noise source. When the windows having the same acoustic performance were installed, the SPL in each room resulted in nearly the same values.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.564-569
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• 1997

본 연구에서는 cabin내의 소음 및 외부 소음 저감을 위한 연구개발 과정을 단계별로 소개하고, 설계변경을 위한 다양한 소음 측정 및 분석을 통해 최종 목표인 저소음 로더개발에 관한 내용을 소개하고자 한다.

• International Journal of Highway Engineering
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• v.6 no.4 s.22
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• pp.123-136
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• 2004

This study tries to compare the noise difference by various surface treatments and to propose appropriate tinning methods. As literature reviews, longitudinally tined pavement is effective to reduce noise made between tire and pavement surface. Various surface treatments were applied to some sections of test road. In case of car, about 2$\sim$3dB(A) was reduced in the section of uniform space 18mm longitudinal tinning. The peak frequency point for truck case happened between 200 and 600 Hz. The maximum noise of car was measured at about 1000Hz. Therefore, it Is proved that surface treatment methods can have a large affect on noise generation. With a result that friction test, the transverse tined pavement showed better frictional characteristics than the longitudinally tined pavement, but as a whole it came out satisfactory result. Results from this study are of early age, so it is required to check the performance continuously.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.78-83
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• 2000

Exterior noise generated by the aircraft induces a serious noise pollution near the airport. For the prediction of an exterior noise radiation of aircraft an empirical formula is employed to model the acoustic sources. It is shown that the fan/compressor noise is the most dominant part of the acoustic sources in all cases.

• Journal of the KSME
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• v.29 no.5
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• pp.496-506
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• 1989

음향학적 관점에서 살펴본 특성은 소음기 내. 외부의 기하학적이 형상, 온도구배 및 유동에 의한 음파전달 현상의 천이등이 복합적으로 관련되어 있어 명쾌하고도 보편적인 설계 방법은 아직까지 밝혀져 있지 않은 상태에 있다. 따라서 많은 자동차 회사나 소음기의 제작 및 설계 회사에서 나 름대로 축적되어온 자료와 경험에 의하여 적절한 소음기를 설계하고 있으나 그 체계적 정리가 일반기계 공학자에게 널리 알려져 있지 않은 상태이다. 본 글에서는 현재까지 밝혀진 소음기의 성능과, 소음기의 내. 외부의 기하학적 형상 및 온도구배와 유동 등의 관련성을 바탕으로 하여 개념적인 설계 방법을 제시하고 있다. 제시된 방법이 많은 설계 경험을 바탕으로 하여 유도된 것이 아니라 음향학적 관점에서 연구되어온 결과들로부터 도출된 것이므로 현장 실무자 관점에서 볼 때 오류가 있을지 모르나 향후 좀더 현실성 있는 설계 방법의 창출에 일조가 되었으면 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.131-132
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• 2008

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.356-357
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• 2012

• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.786-791
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• 2007

Aerodynamically generated noise is dominant when the train speed approaches 300km/h. This noise sources is caused by the turbulent flow separations or vortex shedding from the train structure. Experiments were performed to investigate the characteristics of aerodynamic noise sources generated from exterior of the KTX trains and HSR-350x, especially from the inter-coach spacing. Measurements of both the inside and outside of the cabin are carried out to investigate the characteristics of the noise. Effect of the size of the mud-flap has been investigated through an wind tunnel test and it has been found that the low frequency noise is strongly dependent on the size of the gap. Also performed is an array measurement to locate different noise sources from the high-speed train. spectral characteristics of exterior noise sources are examined.