• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.260-263
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• 2008

공항에 인접한 주거지역에서 항공기 소음문제로 인하여 거주자들에게 소음피해가 발생하고 있다. 이러한 항공기소음을 저감하기 위한 방법 중 건물외피를 차음성능이 높은 구조로 변경하여 건축물의 차음량을 개선시키는 수음원 대책이 일반적으로 사용되고 있다. 특히 건축물 방음시설 설치는 건물외피 중 외부소음에 가장 취약한 창호의 차음량을 증가시키는 것이 효과적인데, 본 연구에서는 기존 창호에 비하여 차음성능이 높은 창호를 교체 설치하여 건축물의 차음량 개선치를 $L_{max}$, SEL, $L_{eq}$로 각각 검토 비교함과 동시에 창호의 기밀성능을 위한 기밀재 및 추가 모헤어의 설치조건에 따른 차음성능을 검토해 보았다. 측정결과 방음시설 설치 후 항공기소음을 $L_{max}$, SEL, $L_{eq}$로 차음량 개선치를 각각 평가한 결과 1.8dB 이내의 편차를 갖는 것으로 나타났으며, 창의 차음성능 개선치는 기밀재 설치 후 $R'45^{\circ}$,w가 5dB, 기밀재 및 추가 모헤어 설치 후 8dB로 나타났다.

• KIEAE Journal
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• v.4 no.3
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• pp.95-101
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• 2004

As a part of acoustical design, it is often necessary to quantify aspects of an existing environment and to predict the result of adding an acoustical treatment. The most common sources of exterior noise, also termed as environmental noise,(or community noise) are traffic noise, air craft noise, industrial noise, etc. Transportation(air, road, and rail)noise is the dominant and most common source of noise exposure in residential neighborhoods, and the annoyance is its most consequential effect. The road traffic noise becomes aggravated due to the rapid increase of vehicles. It has a great effect on the dwelling environment. Therefore we investigate the characteristics and sources of the road traffic noise through grasping the status of the road traffic noise. In the present study, preceding studies investigated the noise level of urban areas in Seoul were reviewed and the noise level of urban areas in Seoul was measured at first, fifth, tenth, and nineteenth floor for two days of weekdays and two days of weekend.

• The Journal of the Acoustical Society of Korea
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• v.21 no.6
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• pp.576-584
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• 2002

This paper proposes a new denosing method using wavelet packet, to reject unknown external noise and white gaussian ambient noise for measuring the transient noise which is one of the important elements for ship classification. The previous denosing method applied the same wavelet threshold at each node of multi-single sensors for rejecting white noise is not adequate in the underwater environment existing lots of external noises. The proposed algorithm of this paper applies a modified soft-threshold to each node according to the discriminated threshold so as to reject unknown external noise and white gaussian ambient noise. It is verified by numerical simulation that the SNR is increased more than 25㏈. And the simulation results are confirmed through sea-trial using multi-single sensors.

• The Journal of the Acoustical Society of Korea
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• v.10 no.1
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• pp.5-11
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• 1991

Articulation test is a good predictor of spatial speech transmission quality. Like many other languages, articulation testing method using Korean language was proposed in 1989, and which was proved as a valid indicator in rooms with static background noise. In this paper, the testing method is examined in variable noise conditions. According to the experiment performed in 26 classrooms with variable background noise, the proposed articulation testing method using Korean Language is still in variable conditions.

• Journal of IKEEE
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• v.5 no.1 s.8
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• pp.16-23
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• 2001

Passive noise reduction is a classical approach to attenuate industrial noise, and an active noise cancellation has several advantages over the passive noise cancellation. The active noise reduction system offers a better low frequency performance with a smaller and lighter system. This paper presents a simple active closed loop control system which consists of an controller for inverting and compensating the phase delay, a microphone for picking up the external noise, and a loudspeaker for radiating the acoustic out of phase signal to reduce the external noise, and external noise can be reduced after compensating the phase difference to be $180^{\circ}$ in the frequency of maximum value in the amplitude response. The noise of the phase delay covered from $50^{\circ}\;to\;310^{\circ}$ tends to be reduced in the active noise control system and it is possible to obtain a noise cancelling of up to approximately 20[dB] at the ears in the enclosurer.

• 대한공업교육학회지
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• v.33 no.2
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• pp.273-286
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• 2008

Underwater acoustic sensor array can detect acoustic signal in underwater and the sensor array can be mounted in each left, right or front side of the UUV(Unmanned Underwater Vehicle). The sensor array could be conformal array and effected turbulent boundary layer flow noise. Therefore, in this paper numerical simulations were performed to know the how the outer flow noise affect the hydrophone which embedded in the elastomer. Corcos wall pressure model was used as turbulent boundary layer flow noise and this model was applied to the frequency density function. Characteristics of transfer function according the kx wave number were simulated and design parameters were thickness of elastomer, density, and modulus of elasticity. Based on the simulation results when increasing the thickness of elastomer noise reduction was increased. This results can be applied to the design of conformal array of UUV.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.67-72
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• 1996

한진 중공업은 상용 운행 속도 200km/h로 중국 광주-형양간 운행을 목적으로 하는 고속열차를 개발하여 제작을 완료하였다. 중국 철도부 측에서는 한진 고속 열차의 객실 내 소음 수준이 운행 최고 속도에서 65 dBA이하이도록 요구하였으며, 당 연구소에서는 외부 소음원을 가정하여 다양한 실험 및 해석을 통하여 객실 내 소음 수준을 예측하여 이를 설계에 반영토록 하였다.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.70-74
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• 2009

The helicopter development technology is improved by the increasing of computing power and advanced test facilities. The increasing efficiency of fuel consuming by the developing of improved lift-to-drag rotor system is the major issue, the noise reduction for ecology(civil area) and increase of survivability to reduce noise detection(battlefield) also are important. This investigation shows the helicopter external noise flight test methods, conventional military helicopter's(UH-60) experimental results and the numerical modeling method for aero-acoustic of rotor blade and the result of CAA(Computational Aero-Acoustic) for main rotor blade.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.264-267
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• 2008

Relationship between exposure to combined noise sources and community annoyance have been investigated. Social surveys were conducted in urban spaces near the construction site with road traffics. The question relating to noise annoyance was answered on an 11-point numerical scale and 5-point verbal scale according to ISO 15666. The questionnaire also contained demographic factors, interference with daily activities, health-related symptoms, and noise sensitivity. Noise levels were measured in terms of A-weighted equivalent level ($L_{Aeq}$), and noise mapping technique was applied to predict the noise levels of urban spaces. Synthesis curves for the relationship between noise levels and percentage highly annoyed for combined noise sources were derived, and compared to the curves from a single noise source.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.848-851
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• 2014

In a small territory like South Korea, the only alternative to accommodate people in a big city is building apartment house. Exterior traffic noise is not inevitable as the apartment house is set up on wayside or main road is newly established near the area. As the request for quiet environment increases for a better quality of life recently, the exterior noise is considered to be resolved. This study shows the present condition of exterior noise of apartments and reviews a need for the improvement by comparing and analyzing the regulations of main country. Finally, considered the evaluating the interior noise in the apartment house.