• Title, Summary, Keyword: Structural borne noise

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Structural noise mitigation for viaduct box girder using acoustic modal contribution analysis

  • Liu, Linya;Qin, Jialiang;Zhou, Yun-Lai;Xi, Rui;Peng, Siyuan
    • Structural Engineering and Mechanics
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    • v.72 no.4
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    • pp.421-432
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    • 2019
  • In high-speed railway (HSR) system, the structure-borne noise inside viaduct at low frequency has been extensively investigated for its mitigation as a research hotspot owing to its harm to the nearby residents. This study proposed a novel acoustic optimization method for declining the structure-borne noise in viaduct-like structures by separating the acoustic contribution of each structural component in the measured acoustic field. The structural vibration and related acoustic sourcing, propagation, and radiation characteristics for the viaduct box girder under passing vehicle loading are studied by incorporating Finite Element Method (FEM) with Modal Acoustic Vector (MAV) analysis. Based on the Modal Acoustic Transfer Vector (MATV), the structural vibration mode that contributes maximum to the structure-borne noise shall be hereinafter filtered for the acoustic radiation. With vibration mode shapes, the locations of maximum amplitudes for being ribbed to mitigate the structure-borne noise are then obtained, and the structure-borne noise mitigation performance shall be eventually analyzed regarding to the ribbing conduction. The results demonstrate that the structural vibration and structure-borne noise of the viaduct box girder mainly occupy both in the range within 100 Hz, and the dominant frequency bands both are [31.5, 80] Hz. The peak frequency for the structure-borne noise of the viaduct box girder is mainly caused by $16^{th}$ and $62^{th}$ vibration modes; these two mode shapes mainly reflect the local vibration of the wing plate and top plate. By introducing web plate at the maximum amplitude of main mode shapes that contribute most to the acoustic modal contribution factors, the acoustic pressure peaks at the field-testing points are hereinafter obviously declined, this implies that the structure-borne noise mitigation performance is relatively promising for the viaduct.

A Study of Acoustic Noise Analysis and Reduction Method for Driving CD-ROM (CD-ROM 구동 시 발생소음 분석 및 저감 방안에 관한 연구)

  • 이재승;차성운
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.904-907
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    • 2002
  • Optical disk drive device is improved in rotating speed for faster data reading. In the case of CD-ROM, rotating speed is over 10000 rpm in the practical use. As a result of high rotating speed, unexpected effects as like increasing disk fluctuation and acoustic noise are raised by the air friction on the rotating disk and the eccentricity of rotating parts. The overall acoustic noise of running CD-ROM could be classified into two different characterized noise. The first is the structural-borne noise which is generated from vibrating solid body. By the reason, the signal of structural borne noise has very similar to the signal of surface vibrating one. It has dense noise energy at specific frequency region. The other is the air-borne noise which is generated from turbulence or vortex caused by friction between disk and air. The signal of air-borne noise has no dominant peak point at acoustic pressure-frequency domain. The noise energy is widely distributed while comparatively high and large frequency region. The structural-borne noise could be reduced by reducing vibration of structure and in addition it's target reducing frequency is narrow. However the air-borne noise reduction is effectively needed of enclosing method for the noise source located near the disk surface because it is difficult to define target frequency point. In this study, the acoustic noise at driving CD-ROM is classified by the sides of it's character and tried to reduce the overall acoustic noise.

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The Estimation of Structural-Borne Noise and Vibration of the Bridge under the Passage of the Light Rail Transit (경량전철 교량 상부구조의 열차주행에 대한 진동 및 소음 분석)

  • Yeo, In-Ho;Chung, Won-Seok;Kim, Sung-Choon;Kim, Sung-Il
    • Journal of the Korean Society for Railway
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    • v.10 no.1
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    • pp.22-28
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    • 2007
  • During the passage of the train, the railway bridge undergoes vibration and noise. The noise of railway bridge can be occurred from various sources. The wheel-rail contact, noise from machinery parts, structural-borne noise, pantagraph noise and aerodynamic noise of the train work in combination. Running train is one of the most important factors for railway bridge vibration. The repeated forces with equidistant axles cause the magnification of dynamic responses which relates with maintenance of the track structure and structure-borne noises. The noise problem is one of the most important issues in services of light rail transit system which usually passes through towns. In the present study, The vibration and noise of the LRT bridge will be investigated with utilizing dynamics responses from moving train as input data for noise analysis.

Analysis of Sources and Contribution for the Radiated Noise of Drum-type Washing Machine (드럼세탁기 방사소음의 소스 및 기여도 분석)

  • Kim, Ji Man;Jung, Byung Kyoo;Heo, So Jung;Ahn, Se Jin;Jeong, Weui Bong
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.8
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    • pp.628-635
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    • 2014
  • The procedure to estimate the sources of noise and vibrations in a typical drum-type washing machine was presented. The sources should be identified to predict the radiated noise with computational model of structure. Source identification techniques based on singular decomposition were implemented using the measured signals of accelerometers and microphones. The finite element analysis and indirect boundary element analysis were implemented to predict the structural vibrations and the acoustic pressures at the field points. The predicted results by only structural sources were compared with those by both structural and acoustical sources. It was verified that not only the structural-borne source but also air-borne source should be considered to predict the radiated noise with better accuracy. The contribution analysis with respect to the transfer path was also preformed.

Structural and Sound Field Analysis of the High Speed CD-ROM Disk Drive (고속 CD-ROM Drive의 구조 및 음장 해석)

  • Yim, Woong-Sub;Cha, Sung-Woon;Lee, Jae-Seung;Moon, Yong-Rak
    • Proceedings of the KSME Conference
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    • pp.210-215
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    • 2001
  • CD-ROM Drives Rotating high speed as 10000 rpm cause serious noise and vibration problems. At the high speed, dominant noise is Air Borne Noise produced from high-speed airflow and Structure Borne Noise produced from structural vibration. In this research, vibration and sound characteristics in CD-ROM Drive were studied by the use of experimental analysis and computational simulation. Sound intensity techniques and ODS(Operational Deflection Shape) techniques are applied to identify the acoustic noise source of CD-ROM drive. And Computational simulation using SYSNOISE is conducted for describing the noise behavior.

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PROCESS OF DESIGNING BODY STRUCTURES FOR THE REDUCTION OF REAR SEAT NOISE IN PASSENGER CAR

  • Kim, K.C.;Kim, C.M.
    • International Journal of Automotive Technology
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    • v.8 no.1
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    • pp.67-73
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    • 2007
  • This study analyzes the interior noise that is generated during acceleration of a passenger car in terms of car body structure and panel contribution. According to the transfer method, interior noise is classified into structure-borne noise and air-borne noise. Structure-borne noise is generated when the engine's vibration energy, an excitation source, is transferred to the car body through the engine mount and the driving system and the panel of the car body vibrates. When structure-borne noise resonates in the acoustic cavity of the car interior, acute booming noise is generated. This study describes plans for improving the car body structure and the panel form through a cause analysis of frequency ranges where the sound pressure level of the rear seat relative to the front seat is high. To this end, an analysis of the correlation between body attachment stiffness and acoustic sensitivity as well as a panel sensitive component analysis were conducted through a structural sound field coupled analysis. Through this study, via research on improving the car body structure in terms of reducing rear seat noise, stable performance improvement and light weight design before the proto-car stage can be realized. Reduction of the development period and test car stage is also anticipated.

Calculation of Coupling Loss Factor for Small reverberation cabin using Statistical Energy Analysis (통계적 에너지 해석법을 이용한 소형 잔향실의 연성손실계수 측정)

  • 김관주;김운경;윤태중;김정태
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.797-801
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    • 2003
  • The Statistical Energy Analysis is based on the power flow and the energy conservation between sub-systems, which enable the prediction of acoustic and structural vibration behavior in mid-high frequency ranges. This paper discusses the identification of SEA coupling loss factor parameters from experimental measurements of small reverberation chamber sound pressure levels and structural accelerations. As structural subsystems, steel plates with and without damping treatment are considered. Calculated CLFs were verified by both transmission loss values for air-borne CLF case and running SEA commercial software As a result, CLFs have shown a good agreement with those computed by software. Acoustical behavior of air-borne noise and structure-borne noise has been examined. which shows reasonable results, too.

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Booming Noise Reduction of Passenger Cars by Mode Decoupling of Structural-Acoustic Systems (구조-음향 모드 비연성에 의한 차량의 부밍 소음 저감)

  • 고강호;이장무
    • Journal of KSNVE
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    • v.9 no.4
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    • pp.822-827
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    • 1999
  • The reduction of booming noise level and improvement of sound quality in the vehicle interior have been major fields of vehicle NVH for many years. In order to reduce the booming noise this paper proposed a system variable, which takes account of mode shapes and natural frequencies of the structural-acoustic system, measurement points and excitation frequency. By simplifying the system variable, the major contributors of panels inculding roof, roof lining, wind shield glasses, doors and floor to booming noise at a specific frequency was experimentally found. Also the relationships between structural modes of roof lining, one of the major contributors, and acoustic modes of compartment cavity were investigated from the viewpoint fo structure-borne noise. In addition, the roof lining was modified structurally by applying marble sponge to the gap between roof and roof lining. Asthe result of structural modification, the booming noise was reduce at target frequency.

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A Design Process for Structural Borne Noise using Panel Contribution and Design Sensitivity (판넬기여도와 설계민감도를 이용한 구조기인소음 설계프로세스)

  • Kim, Hyo-Sig;Kim, Heon-Hee;Cho, Hyo-Jin;Yoon, Seong-Ho
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.806-811
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    • 2007
  • In this study, we propose a more systematic design process for the structure-borne noise. The proposed way consists of 4 steps: Problem definition, Cause analysis, Development of counter-measure and Validation. Especially, we improved the second step: Cause analysis. According to the PCA(Panel Contribution Analysis), a reduction in vibration of the panels of which panel contribution is positive and larger, results in a reduction in structure-borne noise. We have, however, met the case in which the concept of PCA is no valid in a few vehicle tests. In order to understand this phenomenon, we compared the major panels selected by PCA with the one chosen by DSA(Design Sensitivity Analysis). After investigating the difference between the two results, a more improved process is suggested. The proposed one for the second step in the design process consists of not only the previous way: PCA with deformation analysis results but also DSA. It is finally validated that the proposed design process decreases the sound pressure of the concerned noise transfer function more than 3.5 dB.

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