• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.12 no.6
• /
• pp.405-412
• /
• 2002

Recently, regulations of the government and concerns of people give rise to the interest in exhaust and intake noise of passenger car as much as other vehicles. In these demands, performance prediction software with hybrid method was developed at first. Secondly, robust design was used for improving the noise reduction capacity of intake system with the performance prediction software. On the basis of the existing design, length and radios of each component that was thought to effect on the capacity of intake system was selected. The factors were arranged by using L18 table of orthogonal array and optimum value was obtained.

• Superconductivity and Cryogenics
• /
• v.4 no.1
• /
• pp.28-33
• /
• 2002

디지털 소자 구현에 가장 기본적인 조셉슨 접합의 특성 중 잘 알려진 특성이 아닌 자기장 하에서 접합의 거동을 살펴보았다. 자기장이 접합면에서 평행하게 걸린 경우에는 임계온도 이하에서도 어느 특정 온도에서 저항이 나타나는데 이는 그 때 접합을 투과하는 자속이 단자속의 정수배가 되는 경우에 해당함을 보였다. 이로부터 초전도 전극의 침투깊이의 크기와 온도의존성을 구할 수 있었다. 자기장이 접합면에 수직하게 걸린 경우에는 자기장이 볼텍스의 형태로 전극에 침투하여 전체접합을 볼텍스의 수로 나누는 역할을 함을 보였다. 이로써 자기장이 증가할수록 저항전이 폭이 증가함을 설명할 수 있었고 이는 고온초전도체의 거동을 이해하는 데에도 사용될 수 있음을 보였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.05a
• /
• pp.346-352
• /
• 2002

This paper is the experimental study to estimate the influence of various design parameters on the performance of mufflers with perforated tubes and through-flow partitions. Muffler types considered in the present work include through-flow chamber, through-flow chamber with partition, and cross-flow chamber. The influences of the design parameters on the performance of the mufflers can be outlined as follows. In the case of the through-f]ow type mufflers, increasing the tube thickness and the hole diameter of the perforated tubes does not change the maximum value of the transmission loss but decrease the cutoff frequency. In the case of the through-flow with partitions type mufflers, it is shown that combining a fe w short chambers and long chambers can modify the frequency locations of the resonance frequencies to optimize the performance of the mufflers. For the case of the cross-flow type mufflers, it is shown that the transmission loss of the mufflers is mainly affected by the lower porosity when the porosities are different in both sides of the plug. Overall, it is shown that performance of the through-flow type with partition type mufflers is excellent in the lower frequency region, where the cross-flow type mufflers have better performance in the higher frequency region.

• Journal of KSNVE
• /
• v.7 no.4
• /
• pp.701-708
• /
• 1997

Up to now, numerical methods such as Finite Element Method(FEM) or Boundary Element Method(BEM) have been widely used to find the optimized resonator's position during designing a car intake system. However, these methods are not useful at the first stage of car design since it is not easy to change a numerical model consist of a large mesh size. A software has been developed to cover the defects using 4-pole parameter method. The software is running at Windows 95 environment for a user's convenience. To show its usefulness, it is applied to a real automobile intake system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.349-354
• /
• 2007

This paper considers acoustic analysis of silencer within a Dry vacuum pump. Main object is noise reduction of Dry Vacuum Pump using the silencer. First, we measured SPL and Intensity for noise source identification and then, designed for the silencer corresponding with noise character. 4-pole parameter are used for predicting transmission loss which is one of characteristics of silencer when we designed for silencer. Calculated Transmission Loss to change main effective factor and selected to optimal value using Design of Experiment. Finally, noise reduction is estimated to compare existing silencer with optimal silencer.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.17 no.10
• /
• pp.950-957
• /
• 2007

This paper considers acoustic characteristics of silencer within a dry vacuum pump. The main objective is to reduce noise in dry vacuum pump using the new designed silencer. First, SPL and sound intensity are measured for noise source identification and the new model silencer is designed corresponding to noise characteristics. 4-pole parameters are used to predict the transmission loss which is one of the interest characteristics of the new silencer. The calculated transmission loss is then used to change main effective factor and optimal value is selected by using design of experiment. By conducting an experiment, it is proved that the new designed silencer has reduced noise level by 6 dB(A) more than the original one.

• Journal of KSNVE
• /
• v.9 no.2
• /
• pp.310-316
• /
• 1999

4-Pole parameter method based on an acoustic theory is very popular for the analysis of the acoustic behavior of the car exhaust system. However, this method is applicable only for the simple shape of acoustic elements of the muffler. Numerical methods such as FEM(Finite Element Method) or BEM(Boundary Element Method) can also provide acceptable results for the acoustic analysis of the car exhaust system. Even though these numerical methods have benefits for the analysis of complicated shape of acoustic elements of the muffler, time consuming is another problem during modeling and numerical calculation. Combining benefits of both methods, the new code called the hybrid method for car exhaust system is introduced. And the developed code is utilized for calculation of the transmission loss of a main muffler of an automobile comparing with the experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.05a
• /
• pp.625-628
• /
• 2005

Silencers are extensively used for reducing noise in an exhaust system of internal combustion Engine and fluid machineries. The prediction and measurement of the transmission loss as the acoustic performance of silencers are important in early design stage. In the measurement of transmission loss, the semi-anechoic terminations are general used for reducing unwanted effects by reflecting wave. However it is very hard to remove reflecting wave perfectly. So the research about the error made by reflecting wave is important. The analysis about errors made by reflections and modification techniques are proposed. For an application example, the diesel particulate filter (DPF) is chosen. The transmission loss of DPF is measured with and without considerations of reflecting wave.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.870-874
• /
• 2006

This paper presents designing method to reduce the noise and vibration in the wine refrigerator. To improve the noise and gas pulsation of the compressor the silencer is designed. Base plate of the refrigerator is modified to reduce the vibration by the modal testing. By applying the spring grommet, we can reduce the transmission of the refrigerator of the compressor. We measure PWL and the vibration of LG wine refrigerator and a different wine cellar. As the result of the evaluation, we can rightly take pride in the worldwide recognition of LG wine refrigerator

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.05a
• /
• pp.178-183
• /
• 2003

This paper deals with transmission loss characteristics of the panel type silencer to control low frequency noise. The panel type silencer is composed of many Helmholtz resonators by side branch. Each resonator has high transmission loss on the narrow band of its resonance frequency. Direct arrangement of the resonators increases mainly the magnitude of transmission loss. If we arrange the resonators in a row, the peak and band of transmission loss are increased. This makes the resonator array to have high transmission loss in the broader band. Using this idea, we design a silencer that has broader band characteristics and smaller volume.