• Title/Summary/Keyword: Air-Born Noise

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A Case Study on Inside Noise Reduction of Agricultural Tractor Cab(I) -Analysis of Sound and Sound Intensity Levels- (농용 트랙터의 안전캡 내부 소음 감소에 관한 연구( I ) -소음과 음향 강도 수준 분석-)

  • 유동호;김경욱;김재열
    • Journal of Biosystems Engineering
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    • v.20 no.2
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    • pp.117-126
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    • 1995
  • High level of tractor noise may reduce operator's work performance and cause a hearing problem. This study was carried out to investigate the cab noise of a selected agricultural tractor. The noise was measured and analyzed in terms of sound and sound intensity levels. Form the results it was known that a structure-born noise was induced from the feet-rest and rear floor panel of the cab. The air-borne noise caused mainly by the engine was transmitted into the operator's position through the small openings of cab structures in the operator's lower front area.

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An application of the Statistical Energy Analysis for Absorbing and Soundproofing Materials of Vehicle (자동차용 흡.차음재의 성능분석을 위한 통계적 에너지 기법 적용의 검정)

  • Lee, Chang-Myung;Lee, Jun;Kim, Dae-Gon;Jung, Byoung-In
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.11b
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    • pp.1109-1113
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    • 2001
  • Interior parts of a vehicle are getting important to reduce interior noise of car. Therefore, prior analysis of cabin noise related with interior parts are necessary at first design stage. Recently, Statistical Energy Analysis(SEA) has been suggested as a possible way for meddle of high frequency range analysis with interior parts. This article introduces an example of the application of SEA to predict air born noise of cabin of car.

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Status of Helicopter Rotor Noise Technology Development in KARI (KARI의 헬리콥터 로터 소음관련 기술개발 현황)

  • Hwang, Chang-Jeon;Chung, Ki-Hoon;Song, Keun-Woong;Joo, Gene;Lee, Wook
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.05a
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    • pp.187-192
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    • 2006
  • Helicopter noise has been considered as one of major design factors like a performance and safety since the public acceptance, comfortability and stealth aspects were important for customers. According to the airworthiness regulation, the noise levels in throe different flight conditions shall comply with the specific limits. Main and tail rotors noise is most dominant in far field due to the low and mid range frequency characteristics. It is an air-born noise so That the accurate aerodynamic data is necessary for the accurate noise prediction. In KARI, low noise main and tail rotors as well as analysis codes have been developed since 2000. The approach for low noise main rotor is a kind of tip modifications, so called twin vortices tip to reduce the BVI noise. Analysis results show the 9.3dB reduction in terms of pseudo EPNL. The uneven spacing concept is applied for low noise tail rotor. Three or four decibel noise reduction is achieved by new optimized uneven spacing. Rotor noise and aerodynamic prediction codes have been improved also.

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A Study of Improving Transmissibility for Grommets in Air conditioner Compressor (에어컨 압축기 진동전달률 개선을 위한 그로메트 연구)

  • Park, Hong-Ul;Lee, Jai-Kwon;Mo, Jin-Yong;Park, Deug-Yong;Han, Hyung-Suk
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.11a
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    • pp.651-655
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    • 2004
  • This paper studies the designing method and application for grommets, rubber material used to absorb vibration on the air conditioner compressor. The existing grommet with hardness 40 degrees, EPDM, has the high transmissibility on the compressor that causes additional structure born sound. The problem for EPDM is transformation over long time usage possibly due to its design in which stress is concentrated on a certain position. In order to resolve it, silicon material was previously used with the same design in some models. The vibration performance did improve, but the cost became high. Below are the major developments regarding improvements in compressor rubber material, vibration performance and durability through design change, and new grommet to attain cost reduction. 1 The optimum grommet design for stress even distribution through FEM methods. 2. Comparison for grommet material and design for improved transmissibility. 3. Assess for grommets durability and product applications.

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