• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.711-714
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• 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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.763-766
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• 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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.607-611
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• 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.

• 한국소음진동공학회논문집
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• 제13권11호
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• pp.882-889
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• 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.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.867-871
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• 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.

• 한국소음진동공학회논문집
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• 제19권7호
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• pp.685-692
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• 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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.551-556
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• 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.

• 대한기계학회논문집
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• 제16권9호
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• pp.1615-1626
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• 1992

본 연구에서는 배플이 없는 사각단면을 가진 양단자유의 탄성보에 강구가 횡 방향으로 충돌할 때 발생되는 음압을 M.Sakata와 M.Horii의 방법을 적용하여 구하였으 며, 보의 가속도는 모우드 해석기법을 적용하여 구하였다. 그리고 충돌시 발생되는 충격격과 접촉시간은 허즈(Hertz)접촉이론을 이용하였다.그리고 실험을 통하여 이 론으로 구한보의 가속도, 접촉시간, 방사음압의 결과와 비교하였다. 기존의 연구내 용을 기반으로한 본 논문의 기여부분은 hertz 접촉이론을 본 연구의 시스템에 적용하 여 접촉시간을 실험적으로 검증하였으며 모우드 해석기법을 이용하여 구한 보의 진동 을 실험과 비교하였고, 시스템을 탄성보로하여 M.Sakata의 방법을 적용하여 발생되는 음압을 실험으로 검증한 것이다.

• Journal of Theoretical and Applied Mechanics
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• 제3권1호
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• pp.34-44
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• 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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.1053-1058
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• 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.