• Title/Summary/Keyword: Structural borne noise

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Structural Vibration Characteristics for an Outdoor Units Support of an Air-conditioner (에어컨 실외기 받침대의 구조진동 특성)

  • Ryu, Bong-Jo;Song, Seon-Ho;Lim, Chae-Wook
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.11a
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    • pp.215-217
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    • 2008
  • This paper deals with the structural vibration characteristics for an outdoor units support of an air-conditioner. Even though main noise sources are compressor noise and fluid noise which is caused by the fan, the structural modification of the outdoor units support may affect vibration and noise. In this paper, damping ratios for two kinds of an outdoor units support of an air-conditioner are measured through the modal testing. In order to reduce the structural borne noise due to an outdoor units support of an air-conditioner, four kinds of rubber materials are selected and tested.

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A Study on the Measurement of Dynamic Properties of the Rubber Mount in the Impeller Fan Motor of the Air-conditioner (에어컨 실내기 팬 모터용 방진고무의 동특성 측정에 관한 연구)

  • Choi, Hyun;Kim, Jun-Woo;Kang, Tae-Ho
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.11a
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    • pp.185-190
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    • 2001
  • The structure borne noise of the air-conditioner, which degrades the noise quality, is hardly reduced by the general noise treatments. It can be effectively reduced by eliminating the structural vibration which the noise originates from. The rubber vibration isolator prevents the dynamic force induced by the fan driving motor from exciting the chassis structure, which finally reduces the structure borne noise. The dynamic properties of the vibration isolation system such as the natural frequency of the vibration isolation and loss factor of the rubber isolator, need to be experimentally evaluated. In this paper, these dynamic properties were obtained by the resonant method using the impact hammer for 3 types of the isolator specimens. It is known that the isolation natural frequency of the axial direction of the rubber isolator is two times higher than that of the radial direction, and is proportional to the hardness of the rubber specimen.

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Damping Patch Placement on Outdoor Unit of Air-conditioner by Using Structural Intensity Technique (구조 인텐서티법을 이용한 에어컨 실외기의 제진재 적용)

  • 김규식;진심원;정인화;이정우;강연준
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.7
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    • pp.577-585
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    • 2004
  • In this paper, reactive shearing structural intensity method is extended to damping patches placement on outer panels of outdoor unit of air-conditioner to reduce its structural borne noise. The structural intensity is calculated from the normal velocities of structures that are measured by using a laser scanning vibrometer, and $textsc{k}$-space (wave-number domain) signal processing is used to obtain the spatial derivatives in formulation of structural intensity. This method is applied to the outdoor unit of air-conditioner on shaker-exciting mode and operating mode. and then damping patches are placed over area of high reactive shearing structural intensity for reducing the radiated noise. Experimental results show the largest reduction of sound pressure level of an outdoor unit by appling small damping patches to optimal position.

Improved Design Process for Interior noise in Passenger Vehicles (자동차 실내소음을 위한 개선된 설계 프로세스)

  • Kim, Hyo-Sig;Kim, Heon-Hee;Yoon, Seong-Ho
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.04a
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    • pp.974-979
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    • 2008
  • A design process for the structure-borne noise in a passenger vehicle is presented. The proposed process is improved from the previous one. The major difference between the current and last ones is that most of the countermeasures should be developed before fixing a tool for structural parts. This is requested for QCDP(Quality, Cost, Delivery and Productivity) by the design engineers. The proposed one consists of 4 steps: Problem definition, Cause analysis, Development of counter-measure and Validation. Based on the general rule: divide and conquer, the complex problem can be simplified into a few critical sub-systems through the first step: Problem definition. Secondly, the critical causes can be identified for the critical sub-systems through the second step: Cause analysis. Thirdly, effective countermeasures are investigated and produced through the third step: Countermeasure development. The proposed countermeasures are finally validated in the forth step: Validation.

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Noise reduction of a vehicle acoustic cavity sample using coupled Structural-Acoustic element analysis (구조-음향 연성해석을 통한 모형차실 모델의 소음저감 기술연구)

  • 김태정;강성종;서정범
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1994.10a
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    • pp.288-294
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    • 1994
  • A study of prediction and qualification techniques for structure borne booming noise is presented in this paper. Result from acoustic normal mode finite element analysis of a 1/2 size vehicle cavity sample model is compared to the that from an experiment. Coupled structural-acoustic analysis is performed on a 1/4 size vehicle cavity sample model surrounded by 2 mm thick normal steel plates. Interior noise levels around passensger's ear position are predicted and reduced by structural modification based on panel participation factor analysis about the sample cavity model. Futhermore, optimization technique in application of anti-vibration pad is studied.

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Prediction of Interior Noise Caused by Tire Based on Sound Intensity and Acoustic Source Quantification (공기 기인 소음 분석과 음향 인텐시티법을 이용한 타이어에 의한 실내 소음 예측)

  • Shin, Kwang-Soo;Lee, Sang-Kwon;Hwang, Sung-Uk
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.23 no.4
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    • pp.315-323
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    • 2013
  • Tire noise is divided into a road noise(structure-borne noise) and a pattern noise(air-borne noise). Whilst the road noise is caused by the structural vibration of the components on the transfer path from tire to car body, the pattern noise is generated by the air-pumping between tire and road. In this paper, a practical method to estimate the pattern noise inside a passenger car is proposed. The method is developed based on the sound intensity and airborne source quantification. Sound intensity is used for identifying the noise sources of tire. Airborne source quantification is used for estimating the sound pressure level generated by each noise source of a tire. In order to apply the airborne source quantification to the estimation of the sound pressure, the volume velocity of each source should be obtained. It is obtained by using metrics inverse method. The proposed method is successfully applied to the evaluation of the interior noises generated by four types of tires with different pattern each other.

Identification of the Interior noise Generated by Car Axle and Modification of the Structural on Axle System for Noise Reduction (SUV 용 액슬의 소음원 규명 및 소음 저감을 위한 액슬의 구조변경에 관한 연구)

  • Lee, Ju-Young;Lee, Sang-Kwon;Jo, Yoon-Kyeong;Kim, Jong-Youn
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.11b
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    • pp.180-185
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    • 2005
  • Gear whine noise of the axle and transmission is getting more important for reduction of vehicle noise, because major noise of vehicle was reduced. Therefore, in this paper, axle noise and vibration is measured, then the modal analysis and running modal analysis is applied for identification of axle gear whine noise. And To reduce axle noise, Various structural modifications are performed by using FEM and BEM techniques.

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Damping Layout Optimization to Reduce Structure-borne Noises in a Two-Dimensional Cavity (이차원 공동의 구조기인소음 저감을 위한 제진재의 최적배치)

  • Lee Doo-Ho
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2006.04a
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    • pp.805-812
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    • 2006
  • An optimization formulation is proposed to minimize sound pressures in a two-dimensional cavity by controlling the attachment area of unconstrained damping materials. For the analysis of structural-acoustic systems, a hybrid approach that uses finite elements for structures and boundary elements for cavity is adopted. Four-parameter fractional derivative model is used to accurately represent dynamic characteristics oJ the viscoelastic materials with frequency and temperature. Optimal layouts of the unconstrained damping layer on structural wall of cavity are identified according to temperatures and the amount of damping material by using a numerical search algorithm.

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The Study on ODD Acoustic Noise Reduction by Using Micro Muffler (마이크로 머플러를 이용한 ODD소음 저감에 관한 연구)

  • Moon, Byeong-Gi;Cha, Sung-Woon;Lee, Byung-Hee
    • Transactions of the Society of Information Storage Systems
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    • v.2 no.1
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    • pp.50-55
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    • 2006
  • As high performance and high speed have been accomplished by technology of optical disk drive. optical disk drives have gradually high percentage of the market share in market of storage devices. This technology helps to improve the quality of record/reproduction. However, simultaneously it causes various problems in the structural aspect and increases noise largely. Especially at high speed, dominant noise is more influenced by fluid noise than by structure-borne noise. The purpose of this study is that reduce the air-born noise in optical disk drive as it decreases a quantity of flow by using a micro muffler. The micro muffler is a miniaturized muffler. The muffler is used widely by solution to reduce air-borne noise which is generated by flow. According to frequency band of the noise source, it can be applied by muffler of various forms. In this study, we examined the acoustic characteristics of the micro muffler and applied it to reduction of the ODD noise. It could get an excellent noise reduction in high frequency band through the decrease of an inner flow. But it could not get a noise reduction in low frequency band.

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