• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.871-875
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• 2001

Evaluation of the contribution of each pass-by noise source to the overall pass-by noise is an important issue for reduction of pass-by noise. A lead-wrapping test for analyzing pass-by noise of motorcycle is used to identify the principal noise sources of the pass-by noise in this study. Lead-wrapping test is employed and the contribution analysis is carried out. Based on the contribution analysis of each pass by noise source from the action of the prior tests, the design modifications of intake/exhaust systems were performed for reducing the pass-by noise. Finally, the pass-by noise test based on ISO362 was carried out to verify the noise reduction.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.5
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• pp.121-129
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• 1999

Recently, the regulations from the govemment and the concems of the people give rise to the interest in exhaust noise of passenger car as much as other vehicles. The exact analysis of various mufflers is needed to reduce the level of exhaust noise. In this paper, we propose a design to improve the mufflers capacity by reducing noise of exhaust system combining Taguchi method and fractional factorial design. In order to measure the performance of a muffler, the performance prediction software which is developed by the Dept. of Automotive Engineering at Hanyang University is used. From the current muffler system we select control factors such as lenght and radius of each component that are thought to be effective on capacity of muffler. Factors are arranged using L18, L27 table of orthogonal array and the fractional factorial design for analysis. We find some significant interaction effects using 1/3 fractional factorial design and accomplish the reduction of noise from the muffler.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.587-588
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• 2014

Studies that the vehicle exhaust system applied by the TEG(thermal electric generator) are actively in progress in order to improve the fuel efficiency of the vehicle. Vehicle exhaust system is on a poor vibration condition, it is susceptible to TEG. This paper is about the development of vibration durability test of TEG mounted on a vehicle exhaust system. Vehicle driving tests are performed to measure the vibration condition of the vehicle exhaust system. The vibration durability test mode of TEG is evaluated using equivalent vibration energy method. The vibration durability tests of TEG are performed using the multi-axial vibration simulation table.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.2
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• pp.90-100
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• 2015

Recently, creating a signature sound for a brand has become more important in the automotive industry. It is important to remember that the people inside a vehicle are not the only one, who assess the signature sound, exhaust sound has become a more important factor. Most research has used psycho-acoustic parameter to objectively measure the aesthetic qualities of exhaust sound. However, these results do not parallel the results from subjective analysis. Therefore, this research focused on developing a method for objective quantification to assess the aesthetic qualities of exhaust sound in order to help develop a more appealing signature sound. To do so, the actual exhaust sound was synthesized and subjectively assessed at varied frequencies samples of 30 individuals employed at sejong R&D center. The results were analyzed using the science of harmony scale.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.5
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• pp.126-135
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• 1995

An exhaust muffler is one of the simple and effective means to meet the demand for a quiet vehicle, and it deserves a close attention to effectively reduce the engine noise. The transfer function technique is one of the tools that have been used to analyze the noise characteristics of the exhaust muffler. In this paper we obtained a transfer function using the forward-going and backward-going components of sound pressure in the exhaust muffler, which is compatible wiht lattice filter algorithm. This form of transfer function is obtained for the basic elements of a muffler, such as uniform tube, open termin- ation, closed termination, anechoic termination, expansion, contraction, extended-tube resonator, hole, Helmholtz resonator, and concentric hole-cavity resonator. The results are combined to produce the transfer function of various types of mufflers. With this transfer function we calculate the transmission and insertion losses of mufflers, and examined the effects of various design parameters. Comparisons were made between the calculation and experimental results, which showed a good agreement, and we conclude that the transfer function of lattice form can be used to analyze the noise characteristics of the exhaust mufflers.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.821-832
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• 2011

Recently, the noise of vehicle is the one of the key factors for customers to purchase a vehicle and the most important part which is related to the noise is the exhaust system. Thus, car makers have their own ways to assess this exhaust noise not only to decrease the level of noise but to enhance the feeling of it. Typically, to do these things in the early stage of development, the tuning code of the exhaust system has to be made by CAE tool, which is very reliable but expensive, and the prototype parts of this code would be made for the validation test. Then this process can be iterated to meet the target of the performance. In this study, a new algorithm which adapts the '3 dimensional convective sound wave theory 'and 'Doppler effect' has been developed. With this new algorithm, a brand new system for the calculation of tail pipe noise has been developed and validated by acoustic wind tunnel test. As a result of this study, various comparisons and have been carried out, for example, the comparison with other CAE tool has been performed for the validity and the improvement of the new calculation code could be achieved.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.11
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• pp.1105-1111
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• 2015

The exhaust system is one of the major sources of vibrations, along with the suspension system and engine. When the exhaust system is connected directly to the engine, it transfers vibrations to the vehicle body through the body mounts. Therefore, in order to reduce the vibrations transmitted from the exhaust system, the vibration characteristics of the exhaust system should be predicted. Thus, the dynamic characteristics of the bellows, which form a key component of the exhaust system, must be modeled accurately. However, it is difficult to model the bellows because of the complicated geometry. Though the equivalent beam modeling technique has been applied in the design stage, it is not sufficiently accurate in the case of the bellows which have complicated geometries. In this paper, we present an improved technique for modeling the bellows in a vehicle. The accuracy of the modeling method is verified by comparison with the experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1693-1698
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• 2000

In operating test of medium speed diesel engine, the large noise over 110dBA would be occurred, and silencer should be needed to prevent the transmission of noise through exhaust duct. A near neighborhood of medium speed engine test shop, outbreak of low frequency noise was reported. From the result of noise measurement, it was found that the coupling of engine noise and air column between workshops was main cause of annoying low frequency noise. From this study, 3 ways of reformation methods were proposed; insertion of plenum chamber, placement of baffles, and alteration of direction of exhaust. As a result of these modification, low frequency noise was cancelled out.

• Journal of KSNVE
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• v.9 no.1
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• pp.113-120
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• 1999

A perforated tube nozzle as an exhaust noise suppressor of a high-speed civil transport(HSCT) is proposed. The experimental results for the near and far field sound. the visualization of jet structures and the static pressure distributions in the jet passing through a perforated tube are presented and discussed in comparison with those for a simple tube. It is shown that the perforated tube has an excellent performance to greatly reduce the shock-associated noise and that also the turbulent mixing noise is reduced in the range of a limited jet pressure ratio. This considerable noise reduction is due to the pressure relief caused by the through-flow through the perforated holes. Such a pressure relief results in the transformation of normal shock waves into weak Mach waves of X -type and increases the thrust force of the perforated tube nozzle.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1049-1052
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• 2006

Object of this study is to develop an Stack Silencer System for quieting abnormal noise around power plant. Abnormal noise gets resident people to feel uncomfortable. Stack Silencer System is to minimize pressure loss of exhaust gas and to maximize noise reduction effect from abnormal noise frequency band. Stack Silencer System is installation in stack and absorbing material is an aluminum foam. Reduction effect measures insertion loss of $8.2{\sim}19.4dB$ by Stack silencer installation. After Stack Silencer System installation, pressure loss of exhaust gas measured $5{\sim}9mmH_2O$.