• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.330-330
• /
• 2007

• 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.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.18 no.4
• /
• pp.400-410
• /
• 2008

Reduction of structure-borne noise in the compartment of a car is an important task in automotive engineering. Many methods which analyze noise transfer path have been generally used for structure-borne noise. These methods are useful in solving particular problem but do not quantify the effectiveness of vibration isolation for each isolator of a vehicle. To quantify the effectiveness of vibration isolation, the vibrational power flow measurement has been used for a simple isolation system or a laboratory based isolation system. This paper identifies the transfer path of booming noise in a SUV. The powertrain used for test has a in-line 4cylinder engine and 5-shift auto-transmission. This powertrain is transversely supported by four isolators. We calculated the energy flow throughout four isolator by the measurement of power flow and the contribution of energy flow at each isolator.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.16 no.6 s.111
• /
• pp.582-592
• /
• 2006

This paper presents experimental and analytic methods to reduce interior noise generated by car axle. The test vehicle has a whine noise problem at passenger seats. In order to identify transfer path of interior axle noise, the vibration path analysis, the modal analysis and running modal analysis are systematically employed. By using these various methods, it has been founded that the interior noise generated by car axle was air borne noise. To reduce and predict axle noise, various structural modifications are performed by using FEM and BEM techniques, respectively. Through the modification of the axle structure, the air borne noise of the axle was reduced 3$\sim$4 dBA level.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.18 no.1
• /
• pp.26-34
• /
• 2008

This paper summarizes a design procedure of radiated noise from engine blocks of marine engines. This air-borne noise is one of the significant noise contributors including the aeroacoustic noise due to intake and exhaust and the re-radiation due to structure-borne noise. Excitation forces by engine operations are evaluated taking into account the power generation mechanism from the burning process to the subsequence motion of internal parts; piston, connecting rod, and crank shaft. The acoustic transfer vector method is incorporated to effectively simulate the radiated noise field under the various operation conditions. A contribution analysis for the various excitations to the radiated noise is conducted. It is found that the firing pressure is the main source of the radiated noise, and so the structure of the cylinder can be modified to significantly reduce the radiated noise from the engine block.

• Proceedings of the KSR Conference
• /
• 2006.11b
• /
• pp.305-309
• /
• 2006

In this paper vibration reduction characteristics of floating floors used in railway vehicles are studied. Vibration reduction characteristics are compared through a series of tests for elastically-coupled floor and rigidly-coupled floor. It was found that elastically-coupled floor has larger vibration reduction amount than rigidly-coupled floor. Around the fundamental natural frequency, however, elastic floor has poor vibration reduction effect than rigid floor. Measures to reduce structure-borne noise are also discussed based on the test results. Structure-borne noise for running railway vehicles cannot be reduced by an effort to deviate resonance between natural frequency of floors and major exciting forces. Instead, reducing vibration level of top floor and using covers which have low sound radiation coefficient will be effective for reducing structure-borne noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.817-820
• /
• 2014

지하철 인근 지역에서 차량 통과 시 차륜과 레일의 상호작용으로 인한 진동이 지반을 통하여 건물까지 전파되어 구조전달음이 발생하게 된다. 이러한 구조전달음이 발생하는 지하철 인근 지역에서 도로나 주거단지가 새롭게 조성될 예정인 경우, 완공 이후에 발생하는 구조전달음 영향을 사전에 평가하고 대책을 수립하는 것이 요구된다. 본 논문에서는 국내에 위치한 일부 역사에서의 구조전달음을 측정하고 국외의 예측식을 검토하여 구조전달음의 실측치와 예측치를 비교한다. 따라서 국내 지하철의 구조전달음 예측에 대하여 국외 예측식의 타당성을 검토함으로써 향후 건설될 지하구간 역사의 인근 주거지역에 대한 구조전달음을 예측하는데 기초 자료로 활용하고자 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.04a
• /
• pp.526-531
• /
• 2011

A dash panel component, close to passengers, plays a very important role to protect heat and noise from a power train. Meanwhile, it is also a main path that transfers vibration energy and eventually radiates acoustic noise into the cavity. Therefore, it seems important to provide an optimal design scheme incorporating sound packages such as dash isolation pad and carpet, as well as structures. The present study is the extension of the previous investigation how design variables affect sound radiation, which was carried out using the simple plate and framed system. The system taken into account in this paper is a dash panel component of a sedan, which includes A pillar, front side member, dash panel and the corresponding sound packages. Design variables such as panel thickness and sound package layers are investigated how they are related for the better radiation performance (i.e. structure-borne) and sound transmission loss (i.e. air borne).

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.18 no.11
• /
• pp.1177-1184
• /
• 2008

URN(underwater radiated noise) is one of the important performances of the battle ship related to the stealth. The main source of the URN is the structure-borne noise on the hull. And the pipe vibration transmitted to the hull is the main source of the structure-borne noise when the speed of the ship is lower than CIS(cavitation inception speed). In this paper, the vibration isolator(rubber mount) for the pipe system is described in order to reduce the structure-borne noise transmitted to the hull. The vibrations on the sea-water conveying pipes and their supports are measured in order to know how much vibration occurs on those positions. Based on these test results, the improved design of the rubber mount is suggested by the parametric study and is verified numerically with the pipe and hull model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.54-60
• /
• 2006

This study looks over the relation between propeller and noise in ship stern structure. Near field noise and vibration measurements are compared with the analytical results using wave number method. To avoid singularity in wave number integration method, fast field method is introduced. Analytical results show that main transmission mechanism of high frequency noise is structure-borne type and that of low frequency noise is a air-borne type.