• Title/Summary/Keyword: acoustic vibration

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A Vibration Mode Analysis of Resilient Mounting System and Foundation Structure of Acoustic Enclosure using Finite Element Method (유한요소법을 이용한 음향차폐장치용 탄성마운트 시스템 및 받침대의 진동모드 해석)

  • 정우진;배수룡;함일배
    • Journal of KSNVE
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    • v.9 no.3
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    • pp.493-501
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    • 1999
  • The vibration modes of resilient mounting system and foundation structure which support diesel engine/generator set and acoustic enclosure walls play an important role in the vibration transmission process. So, it is necessary to perform vibration mode analysis of resilient mounting system and foundation structure. For some reasons, if the vibration modal analysis of resilient mounting system and foundation structure of acoustic enclosure could be simultaneously done by finite element method, it would be very efficient approach. In this paper, vibration modal analysis method using finite element method for multi stage mounting system having n d.o.f model was proposed. Vibration analysis of single and double stage resilient mounting system was performed to verify the validity of the proposed method. Also frequency response results were compared in case of rigid foundation model and finite element foundation model which was compared with experimental modal analysis results.

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FEM acoustic modal analysis due to location of acoustic baffles to avoid acoustic resonance in the tube bank of boiler for power plant (보일러 튜브군의 음향공진 회피를 위한 음향배플의 위치에 따른 FEM 음향모드해석)

  • Ahn, Sung-Jong;Ju, Young-Ho;Kim, Cheol-Hong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2012.04a
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    • pp.150-154
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    • 2012
  • A flow induced mechanical vibration and acoustic resonance should be considered at design stage because they are mainly occurred in the tube bank of boiler. Acoustic resonance is occurred when the vortex shedding frequency of tube bank coincides with the acoustic natural frequency of the cavity. Effective solution to avoid acoustic resonance is installing acoustic baffles in the tube banks parallelly inside of the flow cavity. Thus, location and number of acoustic baffles should be exactly calculated to eliminate the acoustic resonance. This paper presents case study of acoustic resonance due to inappropriate number and location of acoustic baffles. Measured frequency and mode in the study is verified by FEM acoustic modal analysis. The number and location of acoustic baffles to avoid acoustic resonance are calculated by using FEM acoustic modal analysis.

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Acoustic Analysis in the Payload Fairing of Launch Vehicle (위성 발사체 페어링 내부음향 해석)

  • Seo, Sang-Hyeon;Park, Soon-Hong;Jeong, Ho-Kyeong;Jang, Young-Soon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.12
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    • pp.1146-1151
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    • 2011
  • Acoustic load from rocket propulsion system is main source of random vibration working on the payload. To protect payload from this acoustic load, additional APS(acoustic protection system) is generally applied. Noise reduction capacity of APS can be verified through acoustic test and vibro-acoustic coupled analysis. This paper compared the results of acoustic test and vibro-acoustic coupled analysis about KSLV-I payload fairing with APS.

The numerical analysis of heavy-weight impact noise for an apartment houses considering acoustic mode (Acoustic mode 를 고려한 공동주택 중량충격음 소음해석)

  • Mun, Dae-Ho;Hwang, Jae-Seung;Park, Hong-Gun;Hong, Geon-Ho;Im, Ju-Hyeuk
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2009.04a
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    • pp.394-402
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    • 2009
  • To investigate the heavy-weight impact noise of apartment houses, numerical analysis was performed. The analysis acoustic pressure consider acoustic mode by finite element method. The variables considered effecting on the acoustic pressure are the Acoustic mode, acoustic damping, and the impulse load. The heavy-weight impact noise is a changeable value in the room. Since the most part of the frequency component of heavy-weight impact noise has low frequency. The noise in low frequency is related to the vibration of structure, the reflection of acoustic wave caused by wall and the standing wave called by acoustic mode. The prediction by the numerical analysis was verified with test result of the heavy weight-impact noise at apartment houses.

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Acoustic Analysis in the Payload Fairing of Launch Vehicle (위성 발사체 페어링 내부음향 해석)

  • Seo, Sang-Hyeon;Park, Soon-Hong;Jeong, Ho-Kyeong;Jang, Young-Soon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2011.10a
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    • pp.196-201
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    • 2011
  • Acoustic load from rocket propulsion system is main source of random vibration working on the payload. To protect payload from this acoustic load, additional APS(acoustic protection system) is generally applied. Noise reduction capacity of APS can be verified through acoustic test and vibro-acoustic coupled analysis. This paper compared the results of acoustic test and vibro-acoustic coupled analysis about KSLV-I payload fairing with APS.

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Study on the Reduction of Vibration, Acoustic Noise of SRM by DC Excitation Commutation Method (SRM의 직류여자 전류방식에 의한 진동, 소음의 저감 대책에 관한 연구)

  • Hwang, Yeong-Mun;Jeong, Tae-Uk;O, Seong-Gyu;Chu, Yeong-Bae
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.49 no.1
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    • pp.1-8
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    • 2000
  • Switched reluctance motor(SRM) has simple magnetic structure, and requires simple power electronic driving circuit. It is very useful for wide range adjustable speed drive system. But, SRM drive generates large vibration and acoustic noise because it is commutated individually by step pulse m.m.f of each phase pole. In the vibration and acoustic noise characteristics. The considerable vibration and noise is induced by radial deforming of stator, so the frequency of dominant vibration and noise is coincident with the frequency of natural mode frequency of mechanical structure. This radial vibration force is generated in the phase commutation region. This paper suggests the new electromagnetic structure of SRM with auxiliary commutation winding which is excited by direct current. This phase and commutation winding are coupled magnetically between one phase winding and the other. Therefore, the switch-off phase current is absorbed by the another phase winding. By this interaction of phase and commutation winding in commutation mechanism, vibration and noise is reduced. And this reduction effect is examined by the test of prototype machine. As a result, SRM with DC exciting commutation winding is very useful to reduce vibration and acoustic noise.

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The Prediction of Weak Point about Vehicle Booming Noise Using the Acoustic Transfer Function (음향전달함수(ATF)를 이용한 부밍 소음 취약부 예측 연구)

  • Hwang, K.H.;Oh, H.J.;Choi, S.C.;Suh, J.K.;Hong, S.G.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2014.10a
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    • pp.336-340
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    • 2014
  • The noise and vibration have been evaluated by using the finite element model in the vehicle developing stage. The sound pressure of the vehicle compartment is predicted by the acoustic cavity model coupled with the body structure. In general, the structural model has been focused to study in the improvement of the noise. It is not easy to treat the structural model, instead the acoustic cavity model is relatively simple and aids in root cause analysis of vibro-acoustic issues. Therefore, the acoustic transfer function of the cavity is more efficient for finding out the main contribution parts of the vehicle booming noise. And examples about the run-up booming noise demonstrate the validity of the AFT analysis for improving the vibro-acoustic sensitivity.

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The Analysis of Transmission Characteristics of Closed Structure with Internal Source Using FEM/BEM (유한.경계요소법을 이용한 내부음원을 갖는 닫힌 구조물의 차음 특성 해석)

  • Won, Sung-Gyu;Jung, Weui-Bong;Seo, Yeung-Soo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.05a
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    • pp.318-321
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    • 2005
  • In vibro-acoustic analysis, the commercial CAE tools, such as SYSNOISE, is usually used to take into account of the coupled effects of fluid acoustics and structural vibration. The acoustic field can be solved by either FEM or BEM, while the vibration field is usually solved by FEM. The interior or exterior acoustic problems with the coupled effects of the structural boundary could be solved by the commercial tools. The commercial tools, however, could not solve the problems in case that both the interior and exterior acoustic field is coupled with the structural boundary. In this paper, a realistic method based on FEM/BEM coupling scheme is presented to analyze the acoustic radiation from the internal source in a chamber to external acoustic field through elastic structural boundary. Several numerical examples are implemented to validate the developed program.

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Acoustic Analysis and Design of a Direct-Radiator-Type Loudspeaker (직접방사형 스피커의 음향특성 해석및 설계)

  • 김준태;김정호;김진오
    • Journal of KSNVE
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    • v.8 no.2
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    • pp.274-282
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    • 1998
  • A systematic procedure for designing a direct-radiator-type loudspeaker has been developed, based on the numerical vibro-acoustic analysis and the Taguchi method. The finite-element model of the speaker cone has been used to calculated the vibration response of the cone excited by the voice coil. The vibration displacement of the speaker cone has been converted into the vibration velocity and used as a boundary condition for the acoustic analysis. The acoustic frequency characteristics of the loudspeaker have been calculated by the boundary element method. The numerical results have been verified by the experiments carried out in an anechoic chamber. Some design parameters have been selected by using the Taguchi method, and the variations of the acoustic characteristics due to the changes of the parameter values have been examined using the numerical model.

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Acoustic characteristics of a loudspeaker obtained by vibration and acoustic analysis (진동/음향 해석에 의한 스피커의 음향특성 연구)

  • Kim, Jung-Ho;Kim, Jun-Tai;Kim, Jin-Oh;Min, Jin-Ki
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.10
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    • pp.1742-1756
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    • 1997
  • The acoustic characteristics of a direct radiator type loudspeaker has been studied in this paper. The natural modes of the speaker cone vibration analyzed numerically by the finite element method have been verified by comparing them with experimental results. The so-ap-proved finite-element model has been used to calculate the vibration response of the cone excited by the voice coil. The vibration displacement of the speaker cone paper has been converted into the vibration velocity and used as a boundary condition for the acoustic analysis. The frequency characteristics, directivity, and sound pressure distribution of the loudspeaker have been calculated by the boundary element method. The numerical results have been verified by the experiments carried out in an anechoic chamber. The variations of the acoustic characteristics due to the changes of some design parameter values can be examined using the numerical model.