• Title/Summary/Keyword: Acoustic modal analysis

Search Result 76, Processing Time 0.028 seconds

Vibro-acoustic Analysis of Simplified Satellite Model by Using the Statistical Energy Analysis Technique (단순화된 위성체의 통계적 에너지 해석법을 이용한 음향-진동 연성 해석)

  • Jeong, Cheol-Ho;Ih, Jeong-Guon;Moon, Sang-Moo;Kim, Hong-Bae
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2002.11b
    • /
    • pp.711-714
    • /
    • 2002
  • At the lift-off condition, the combustion and Jet noise of launch vehicle produces a severe acoustic environment and the acoustic loads may be damaging to paylaod and equipments. Prediction of the acoustic environment is thus needed to support the load-resistive design and test-qualification of components. Currently, such a high frequency problem is usually dealt with by using the SEA technique, for which the assumptions should match reasonably well with the vibro-acoustic condition of system. The subsystems of SEA model was composed of 16 flat plates, 8 L-shaped beams, and 2 acoustic cavities. The frequency range was 400 Hz - 4 kHz considering the modal parameter. The experiment was performed in a high intensity acoustic chamber, in which the diffuse acoustic field was assured. By comparing the SEA analysis and the experiments, the error less than 5 dB was observed.

  • PDF

Multidisciplinary Design Optimization for Acoustic Characteristics of a Speaker Diaphragm (스피커 진동판의 음향특성 다분야통합최적설계)

  • Kim, Sung-Kuk;Lee, Tae-Hee;Lee, Surk-Soon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2004.11a
    • /
    • pp.763-766
    • /
    • 2004
  • Recently, various acoustic artifacts that contains speaker have been produced such as cellular phone. Speaker consists of diaphragm generating sound and coil vibrating diaphragm. Generally, good speaker means that it has a wide frequency range, high output power rate to input power and flat sound pressure level in specified frequency range. Acoustic characteristic was estimated through the experiment and computer simulation, or sound power was controlled with acoustic sensitivity in a natural frequency range fer last decade. However, the flatness of sound pressure level has not been considered to enhance the sound quality of a speaker. Tn this study, a method for speaker design is proposed for a good acoustic characteristic, which is flatness of SPL(sound pressure level) and wideness between the first and second natural frequency. SYSNOISE is used fer acoustic analysis and ANSYS is used for harmonic response analysis and modal analysis. Optimization for acoustic characteristics of a speaker diaphragm is performed using ModelCenter. All analyses are done within a frequency domain. And we confirm that the experimental and computational simulations have similar trend.

  • PDF

Comparison of various methods to obtain structural vibration for vibro-acoustic noise (구조 방사 소음의 해석을 위한 구조물의 진동 획득 방법의 비교)

  • Wang Se-Myung;Shin Min-Cheol;Koo Kun-Mo;Kim Dae-Sung;Bae Won-Ki;Kyong Yong-Soo;Kim Jung-Seon;Kook Jung-Hwan;Thuy Tran ho Vihn
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2006.11a
    • /
    • pp.607-611
    • /
    • 2006
  • There are several methods to obtain structural vibration for analysis of vibro-acoustic noise. First of all, vibration data can be obtained through the structural analysis using finite element method. Although this method has no need to experiment, the analysis result is unreliable when the structure and the vibration source is complex to model exactly. The second method is to measure vibration using a number of sensors. The analyzed vibro-acoustic noise with directly measured data is setting morereliable when the number of data acquisition points is getting larger. However, it requires large amount of time and effort to measure all vibration data on every node especially when the size of vibrating structure is large. The Modal Expansion Method(MEM), which uses mode information and measurement data, has been introduced to compensate their limits. With a relatively small number of measurement data, the reliable structural vibration for vibro-acoustic noise can be obtained using this semi-analysis method. Although MEM gives reliable result, it is restricted by the number of modes and measurement points. In this paper, structural analysis, direct vibration measurement method and MEM are compared using the simple aluminum box model. Furthermore, the washing machine case is also provided as a comparative example. The Laser Doppler Vibrometer(LDV) was used instead of contact type accelerometer to get vibration data.

  • PDF

Structure Borne Noise Analysis of a Flexible Body in Multibody System (다물체계내 유연체의 구조기인 소음해석)

  • 김효식;김창부
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.13 no.11
    • /
    • pp.882-889
    • /
    • 2003
  • This paper presents the method for structure borne noise analysis of a flexible body in multibody system. The proposed method is the superposition method using the flexible multibody dynamic analysis and the finite element one. This method is executed in 3 steps. In the 1st step, time dependent quantities such as dynamic loads, modal coordinates and gross body motion of the flexible body are calculated through a flexible multibody dynamic analysis. And frequency response functions of those time dependent quantities are computed through Fourier transforms. In the 2nd step, acoustic pressure coefficients are obtained through structure-acoustic coupling analyses by the finite element method. In the final step, frequency responses of acoustic pressure at the acoustic nodes are recovered through linear superposition of frequency response functions with acoustic pressure coefficients. The accuracy of the proposed method is verified in the numerical example of a simple car model.

A Study on the Reduction of Booming Noise of an Automobile (승용차의 부밍 소음 저감에 관한 연구)

  • 이상현;강상욱;최형길;이장무;성명호
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • 1996.11a
    • /
    • pp.867-871
    • /
    • 1996
  • Recently many studies have been carried out to predict the characteristics of vehicle noise and to reduce the noise for enhancing the ride quality. In this study, the structural-acoustic coupling theory and the acoustic finite element theory were reviewed, and the structural acoustic coupling analysis was applied to an automobile. Because of nonuniformed lateral shape of a compartment cavity, the acoustic modes were calculated with 3-D finite element modeling. The structural modes were measured with the modal testing. Using the structural-acoustic cooling analysis, the modes which strongly coupled to the interior noise were identified and the boundary regions which could reduce noise level efficiently by structural modification were predicted.

  • PDF

FE Analysis for Fundamental Air-cavity Resonant Frequency of Tire (타이어의 첫 번째 공기공동 공명에 관한 유한요소해석)

  • Kim, Yong-Woo;Bang, Sung-Huyn
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.19 no.7
    • /
    • pp.685-692
    • /
    • 2009
  • Vehicle interior noise is the results of numerous sources of excitation. One source involving tire pavement interaction is the tire cavity resonance and the forcing it provides to the vehicle spindle. Using a simplified model for the tire acoustic cavity system only, we formulated finite element equation to predict the fundamental acoustic cavity resonant characteristics inside tire-wheel assembly of undeformed and deformed tire. Combining the finite element analysis with experimental verification, we explained the acoustic characteristics theoretically. Especially, we have shown that the difference between the first two resonant frequencies increases as the deformation of deformed tire increases.

FE Analysis for Fundamental Air-Cavity Resonant Frequency of Tire (타이어의 첫 번째 공기공동 공명에 관한 유한요소해석)

  • Kim, Yong-Woo;Bang, Sung-Hyun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2009.04a
    • /
    • pp.551-556
    • /
    • 2009
  • Vehicle interior noise is the results of numerous sources of excitation. One source involving tire pavement interaction is the tire cavity resonance and the forcing it provides to the vehicle spindle. Using a simplified model for the tire acoustic cavity system only, we formulated finite element equation to predict the fundamental acoustic cavity resonant characteristics inside tire-wheel assembly of undeformed and deformed tire. Combining the finite element analysis with experimental verification, we explained the acoustic characteristics theoretically. Especially, we have shown that the difference between the first two resonant frequencies increases as the deformation of tire due to vertical load increases.

  • PDF

A Study on the Vibration and Acoustic Radiation from an Elastic Free- Free Beam due to a Steel Ball Impact (강구의 충돌에 의한 양단자유 보의 진동 및 음향 방사에 관한 연구)

  • 박홍철;이효근;박윤식
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.16 no.9
    • /
    • pp.1615-1626
    • /
    • 1992
  • In this study, vibrations and resulting acoustic radiations from an elastic beam impacted by a steel ball were studied theoretically and experimentally. First the transverse vibrations of free-free elastic beams are analysed with modal analysis technique. The impact forces are modeled with the Hertz's theory and the contanct duration is compared with the measured values. Also the calculated beam vibrations are verified with the experimental results. Then the acoustic radiations due to the beam vibration are studied numberically and experimentally. The acousticpressure is calculated assuming the beam has an elliptical cross-section. The predicted acoustic pressure is compared with the measured value. It was found that both the predicted beamvibrations using the Hertz's theory and the estimated acoustic pressure under the assumption of an elliptical cross- section are in very good agreements with the measured values.

ANALYSIS ON THE VIBRO-ACOUSTICAL CHARACTERISTICS OF A PANEL-CAVITY COUPLED SYSTEM

  • Kim, Seock-Hyun;Kang, Sang-Wook;Lee, Jang-Moo
    • Journal of Theoretical and Applied Mechanics
    • /
    • v.3 no.1
    • /
    • pp.34-44
    • /
    • 2002
  • Theoretical analysis Is carried out to identify the modal coupling effect between some particular acoustic modes of a vehicle compartment cavity and vibration modes of body panels like side doors, roof or floor. A simplified panel-cavity coupled model is investigated on the coupled resonance frequencies, modes and frequency response characteristics. Through parametric study, It Is possible to explain how the acoustic response of a coupled system will be determined by the vibration and acoustic property of the individual panel and cavity system. Full coupled system shows some interesting features different from those of the semi-coupled system In frequency, mode and acoustic response.

  • PDF

Development of Software for Dynamic Analysis of Piezoelectric Underwater Transducers (압전 수중음향 센서의 동적해석 프로그램 개발)

  • 최준화;김재환;조치영
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2003.11a
    • /
    • pp.1053-1058
    • /
    • 2003
  • Piezoelectric under water acoustic transducer is a kind of device for under water detection working as not only an actuator but also a sensor. The technique that can predict acoustical characteristics of transducer is important for robust design of transducer in harsh underwater environment. This paper represents the development of software for analyzing dynamic characteristics of piezoelectric acoustic transducers based on finite element method. Modal and transient analysis modulo for acoustic transducers are developed TWO dimensional model for Tonpilz transducer is used for the test of the developed nodal and transient analysis modules. and comparison is made with a commercial code, ANSYS.

  • PDF