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A Study on the Evaluation Metric of a Civil Aircraft Noise (민간항공기 소음평가 단위에 관한 연구)

  • Lee, Jun-Ho
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.5
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    • pp.503-513
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    • 2006
  • The duration time of aircraft noise event is also an important factor for the evaluation of civil aircraft noise, which is considered as a notable characteristic of military aircraft noise. SEL is proved as a suitable noise metric for the measuring military aircraft noise of various flight pattern considering the duration time of noise event. This study reviews whether SEL is a suitable for measuring civil aircraft noise and study shows SEL is fairly compensating the duration time of civil aircraft noise event for the evaluation of aircraft noise. Noise metric for the evaluation aircraft noise based on SEL is more appropriate than based on $L_{MAX}$ for compensating duration time of noise event either military aircraft or civil aircraft. In this reason, current formula of WECPNL based on energy average of measured $L_{MAX}$ for the evaluation of aircraft noise impact in 'Test Method of Noise and Vibration of Korea' is recommended to be amended to formula of WECPNL based on energy average of measured SEL considering compensation of noise event duration time, if WECPNL is not based on measured EPNL, a metric compensating duration time.

The Study of Sound Level Specification of Subway Line II in Busan (부산 지하철 2호선 소음 특성 연구)

  • Jeong Kyung-Won;Yoon Na-Na;Kim Joo-In;Kwak Jin;Kim Yung-Tae
    • Journal of Environmental Science International
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    • v.15 no.3
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    • pp.287-292
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    • 2006
  • The purpose of this paper is to evaluate the noise level and source, reduce the subway line II noise. As a result of measurement of subway line II in Busan the highest value section of uproad line was from Jigegol to Motgol by 89 dB(A). The sections of conversation and listening interference(over 80 dB(A)) were 21 sections(55%) of 38 sections. Among these sections, 15 sections(71%) were produced rolling noise, 3 sections(14%) squeal noise, 2 sections(10%) braking noise and 1 section(5%) fan noise, and then a main noise source was the rolling noise. In case of downroad line, the highest value section was from Busan Metro Art Museum to Centum city, Motgol to Jigegol by 88 dB(A). The sections of conversation and listening interference(over 80 dB(A)) were 18 sections(47%) of 38 sections. Among these sections, 15 sections(83%) produced rolling noise, 2 sections(11%) squeal noise and 1 section(6%) braking noise were investigated in this study. and then a main noise source was the rolling noise.

A Study on Noise Reduction for the Driving System of a Forklift (지게차 구동부의 소음 진동 저감에 대한 연구)

  • Kim, Woo-Hyung;Hong, Il-Hwa;Chung, Jin-Tai
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.1
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    • pp.80-86
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    • 2008
  • In this study. the noise sources were identified and the noise and vibration were reduced for an industrial forklift. To identify the noise sourses, noise signals were measured by a microphone on a driver seat and these signals were analyzed with a waterfall plot. For this purpose, the gear mesh frequencies from the gear box of a reducer were not only investigated but noise/vibration sourses of an electric motor were also examined. Furthermore, the frequency response functions were obtained to confirm the vibration and noise sourses. It was found that severe vibration and noise were generated in the casing and the connecting part of the reducer. The severe vibration and noise could be reduced by a structure modification.

A Strategy of Refrigerator Noise Control by Using Subjective Assessment (주관적 평가방법을 적용한 냉장고 소음대책 수립)

  • 정광일;김석관;이종구;김양한
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.191-196
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    • 2001
  • The conventional methods for noise control attempts to simply reduce the level of product noise. This has been common practice in noise control industry. However, it is very straightforward common sense that we have consider human perception on noise. In this paper, we propose a noise control strategy which takes into account the subjective perception of product noise. We especially has concentrated on a refrigerator noise. The proposed method is composed of 3 steps. Firstly, the actual refrigerator noise signal is measured. Then, to make the sample noise set for subjective assessment the noise signal is edited in 1/3 octave bands. Finally, we establish a strategy of refrigerator noise control by using the results from subjective assessment of these noise signals

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A Study of the Noise Reflection Effect of an Alternator in a 13-liter Turbo-intercooler Diesel Engine (13 리터급 터보.인터쿨러 디젤 엔진의 얼터네이터 소음 반사 효과에 관한 연구)

  • 최성배
    • Journal of the Korean Society of Marine Engineering
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    • v.27 no.3
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    • pp.381-387
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    • 2003
  • Engine noise consists of the noise radiated from an engine structure and noises from engine ancillaries such as a turbocharger fuel injection system, and alternator. The noise of these ancillaries might be incorrectly evaluated in the aspect of the noise contribution to engine noise because the noise reflection effect of their neighbor engine structure is easily ignored. Consequently, noise source identification should be misled. This study investigates the fact that the engine structure located around an alternator reflects alternator noise, and the reflected noise acts as another alternator noise source in a heavy-duty diesel engine. The result shows that the alternator noise can be correctly estimated in engine noise by properly including the noise reflection effect.

Improvement Noise Attenuation Performance of the Active Noise Control System Using RCMAC (RCMAC를 이용한 능동소음 제어시스템의 소음저감 성능개선)

  • Han, S.I.;Yeo, D.Y.;Kim, S.H.;Lee, K.S.
    • Journal of the Korea Society For Power System Engineering
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    • v.14 no.5
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    • pp.56-62
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    • 2010
  • In this paper, a recurrent cerebellar modulation articulation control (RCMAC) has been developed for improvement of noise attenuation performance in active noise control system. For the narrow band noise, a filter-x least mean square (FXLMS) method has bee frequently employed as an algorithm for active noise control (ANC) and has a partial satisfactory noise attenuation performance. However, noise attenuation performance of an ANC system with FXLMS method is poor for broad band noise and nonlinear path since it has linear filtering structure. Thus, an ANC system using RCMAC is proposed to improve this problem. Some simulations in duct system using harmonic motor noise and KTX cabin noise as a noise source were executed. It is shown that satisfactory noise attenuation performance can be obtained.

Experimental Study and Evaluation Method for Sloshing Noise of Fuel Tank on Passenger Vehicle (승용차량용 연료탱크 슬로싱 현상에 대한 실험적 고찰 및 평가 방법에 대한 연구)

  • Ahn, Sejin;Yoon, Seongho
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.6
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    • pp.444-451
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    • 2014
  • The signal patterns of slosh noise produced by the fuel tank of a passenger vehicle are characterized by analyzing vehicle interior noise, fuel tank vibration, and near-field noise radiated from the fuel tank. This paper also shows the noise transfer path analysis results performed from the fuel tank to the vehicle inside. On top of them, physical index is described, demonstrating a good correlation with subjective feeling of slosh noise. It is essential to identify the main noise transfer paths for redesigning of the fuel tank system aiming at reducing slosh noise and also helpful to apply physical index in evaluating and reducing this noise. It is found that structure-borne path is the main root of slosh noise and a value reveals a good correlation with subjective feeling.

Noise Source Identification of the Design Elements of the Driving Gear for the Urban Railway (도시철도용 구동기어의 설계 요소에 대한 소음 기여도 분석)

  • Kim, Kinam;Lee, Hyuncheol;Sun, Chanwoong;Lee, Sungwook
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.25 no.7
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    • pp.470-480
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    • 2015
  • As the railway noise guideline of the Ministry of Environment after 2017 is strictly enforced, the noise level at stationary condition of urban railway is demanding the reduction about 2 dB(A). And the noise level at running condition is reduced by 6 dB(A) at 80 km/h. Therefore, the devices that causes noise shall arrange for the improvement plan of noise reduction for each device. In this paper, we carried out a technical review of the driving gear used to drive the vehicle from a variety of noise-induced equipment of a urban railway. Analyze the causes of the current noise levels and noise cause about the driving gear used in current urban railway and this study analyzes the noise level and noise cause the drive gear being used in the current urban railway. Finally, in this paper proposes a scheme for reducing the noise that can be designed to reduce the noise with considering the noise cause analysis.

A study on the Development of Noise map for quiet environment of urban areas (정온한 도시환경을 위한 소음지도 개발 및 응용연구)

  • 박상규;박인선
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.1182-1186
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    • 2003
  • Noise map is becoming an increasingly important tool supporting noise policy. In order to main am a quiet environment of urban areas, noise map was developed by using GIS technique which combines geographic and noise informations with a database management system. By evaluating various methods of the spatial anal: sis, it was concluded that the inverse distance weighted method gave the best results and was applied to develope the noise maps of road noise.

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Noise Reduction of Reciprocating Type Air Compressors (왕복동식 공기압축기의 소음저감에 관한 공학적 대책 연구)

  • Lee, Kwang-Gil;Park, Jae-Suk
    • Journal of the Korean Society of Safety
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    • v.21 no.5
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    • pp.12-16
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    • 2006
  • This paper deals with the noise evaluation and noise reduction of a reciprocating air-compressor. The reciprocating air-compressor is widely used in the small and medium sized industrial firms, many employees exposed and irritated by their noise in the workplace. Thus, appropriate noise control actions should be taken to prevent hearing loss due to the its noise exposure. Lead-wrapping techniques are employed to identify the contribution of principal noise sources which are generally known to be motor, belts, suction valves, discharge valves, moving parts, and flow-induced noise caused by edges or discontinuities along the flow path including expansions, contractions, junctions and bends. As a result, the main noise sources of the air-compressor are categorized by the suction and discharge noise, valve noise, and compressed air tank noise. Based on the investigations, mufflers are designed to reduce both the suction and discharge noise and the compressed-air tank noise. Instead of the conventional valve plate, polyethylene resin is used the reduction of valve impact noise. In addition, attempts are made to reduce the valve noise propagation to the cylinder head and the compressor tank by using the insulation casings. As a result of the countermeasure plans, a noise reduction up to 10dB(A) could be achieved for the air-compressor.