• Proceedings of the KSR Conference
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• 2007.05a
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• pp.69-72
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• 2007

In this paper, we describe the analysis of interior noise for tilting train that is being developed in Korea. Tilting train is made of composite material to reduce the car body's weight and attached a self-steering system on bogie to improve curving performance. However, the acoustic performance (Transmission Loss) of such material is worse than the materials of conventional train, such as aluminum, steel and so on. Therefore, we measure the transmission loss of side wall / floor of tiling train and predict the interior noise for tilting train using its measuring results

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1415-1418
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• 2007

When a high voltage COS fuse becomes a short circuit by the over current, the impulse noise over 150 dB(A) with the strong pulse jet is radiated from the COS fuse of an electric transformer. For the purpose of the impulse noise reduction, in this study, a reactive type silencer with perforated panels are considered. The transmission loss of the silencer are calculated by transfer matrix method. The effect of the porosity, the distance between panels, and the number of perforated panel on the sound transmission loss is investigated and discussed.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.376-380
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• 2009

The transmission noise characteristics through the ventilating duct was conducted numerically using SYSNOISE. A ventilating system is usually composed of mufflers for preventing noise transmission from the ventilator into indoors through the ducts and distributors for transferring air to or from each room. The transmitted noise characteristics of distributors which have different branch angles and of mufflers having different shapes were analyzed numerically. New duct element combining a muffler and a T-shaped distributor was developed for better noise reduction in this paper. New element's performance was shown numerically.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.1
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• pp.1-7
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• 1991

Degradation of communication quality is due to transmission error rather than quantization noise when DPCM signal is transmitted over a heavily noise channel. The communication quality can be improved by employing an error correcting code to the DPCM signal transmission over such a channel. We considered both quantization noise and transmission error simultaneously in evaluating the signal to noise ratio. To efficiently improve the signal to noise ratio, we analyze the unequal symbol error probability of convolutional code, and encoded to more protect significant symbols from channel errors than least ones, so that the signal to noise ratio is improved. We derived related formulas and also made computer simulations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.731-732
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• 2011

This paper shows a whole noise quality checking system for the new developed 6th speed automatic transmission manufactured in USA. Due to demand for manufacturing of the high NVH quality transmissions in the mass product line, some special checking system called EOL is adapted. This EOL system is using vibration analysis technologies. Through adapting vibration analysis technologies and functions likewise RMS, Crest Factor, Harmonics, Peak, Band, and Order tracking, various noise problems caused by wear, nick, and deformations could be successfully detected and predicted. Therefore, automatic transmissions manufactured in the USA could get high NVH quality.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.710-714
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• 2002

Whenever a noise problem of a product is concerned, a first step is to identify the energy transmission path whether it is an air-borne or a structure-borne. Depending on the characteristic of the noise path, tools on the noise reduction are different. In this paper. an important aspect of the “mass law” in a noise transmission has been investigated. Since an air-borne has 20 dB/Decade, and a structure-borne 10 dB/Decade of a sound transmission loss due to a mass, an engineer who aims to have a light product design should have an enough knowledge on the mass law, especially, the sensitivity of the weight itself. A honeycomb plate is examined as a sample of a light structure to implement a mass law.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.3
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• pp.257-262
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• 2010

Lower tunnels and concrete based tracks are introduced to newly constructed metro lines to reduce the construction and track maintenance fees. But such a lower tunnel together with concrete based track causes higher interior noise of metro trains. It is required that the trains should not only be a transportation media but also be comfortable. So, to lower the metro train's interior noise level, design was made to increase the transmission loss per sectional part. Through such a design, it is expected that about 7 dB(A) of noise level will be reduced compared to that of the conventional train.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.470-475
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• 2001

The elevator gear box with the helical gears needs to be developed instead of the one with the worm gears to improve the efficiency. In order to develop the gear box, the analytical tool to predict the helical gear noise is necessary to meet customer's noise requirement. Gear noise is related to the loaded transmission error. Therefore, the simulation program for the loaded transmission error analysis of the helical gears is developed in this study. Using the developed program, the effects of tooth modification such as tip relief and the extent of tip relief are investigated. Finally, the procedures to determine the tip relief and the extent of tip relief are proposed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.875-880
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• 2002

It is necessary to determine the vibration source and its transmission paths in order to develop a low-noise compressor. Through the use of multiple-input/single-output(MISO) mode1, the transmission paths of vibration within a reciprocating compressor have been investigated. In order to identify the transmission path, we measure the accelerations of the block and transverse vibrations of the line discharge tube. As outputs, vibrations of compressor shell were measured at three positions; cylinder head, one near the suction line, and the top of upper shell. The partial coherence function and transfer function are obtained ken the measured data, and the results are observed in order to determine vibration source and its influence on the shell vibration.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.12
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• pp.2695-2702
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• 2002

The elevator gear box with the helical gears needs to be developed instead of the one with the worm gears to improve the efficiency. In order to develop the gear box, the analytical tool to predict the helical gear noise is necessary to meet customer's noise requirement. Gear noise is related to the loaded transmission error. Therefore, the simulation program fer the loaded transmission error analysis of the helical gears is developed in this study. Using the developed program, the effects of tooth modification such as tip relief and the extent of tip relief are investigated. Finally, the procedures to determine the tip relief and the extent of tip relief are proposed.