• Journal of the Korean Society for Precision Engineering
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• v.16 no.12
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• pp.31-39
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• 1999

Previous researches and experiments have already verified that the primary noise source of high pressure tandem axial thpe piston pump is fluid-borne noise from the process of oil distribution between the kidney-shaped port and valve plate. So, many researchers have improved pressure gradients and reduced sound levels by applying pre-compression and pre-decompression metering grooves to valve plate. In practice however, the sound level of th high pressure tandem axial type piston pump is still undesirable. This paper testified the effect of pumping phase of the piston on vibration and noise of th high pressure tandem axial type piston pump on the best of theoretical research in $this^(1)$. Therefore considering the pumping phase of the piston when assembling the tandem axial type piston pump, it is possible to reduce 1.5~2[dB]of sound level.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.1
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• pp.58-64
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• 2015

There are a lot of different types of noise from construction site and it depends on construction stage, equipment type and number of operating equipments. The problem is that the almost noise from construction site is high level and some kinds of noise levels are over 100 dB. In addition, if construction site is located in downtown, there are a few options to reduce noise level. Therefore several site mitigation plans were developed to reduce different types of construction noises such as breaker work, gang form and asphalt saw. They were applied in site and evaluated noise reduction performance. The test result of site insertion loss was between 4~8 dB depends on the equipment and type of work.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.445-448
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• 2001

Noise radiated from pile driving operation is one of major sources of community noise pollution and thus its operation method is strictly restricted by regulations. Although the drilling method is now used been commonly used in urban areas because of its activity, the benefit of low noise decreases due to high working cost. In the present work, noise characteristics of pile driving operation are carried out. Based on the study result, a low-noise pile cap for driven piles is developed in order to satisfy both the noise level restriction and the economical efficiency. Effects of pile cap are investigated by a scale model experiment, which is focused on the variation of impact force and sound pressure level. The results show a good possibility of noise reduction by an appropriately designed pile cap.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.490-494
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• 2014

There are a lot of different types of noise from construction site and it depends on construction stage, equipment type and number of operating equipments. The problem is almost noise from construction site is high level and some kinds of noise levels are over 100dB. In addition, if construction site is located in downtown, there are a few options to reduce noise level. Therefore several site mitigation plans are developed to reduce different types of construction noises and it is applied in site and evaluated noise reduction performance in this study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1421-1424
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• 2006

Recently Requirement of indoor environment is increased in APT. Among indoor noises of APT, noise of plumbing system in bathroom is very serious problem except of floor impact noise. Plumbing system with wan hanging unit make a good grade and recognition in rating noise of bathroom in grade of house rating. But it is hard to find a data which are measured in APT built. In this study, the effect of noise reduction is checked by measuring the noise of plumbing system with wall hanging unit that is built. As result the upper household's Peak sound level is measured 80dB(A), the under household's peak sound level is measured 40dB(A).

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2594-2599
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• 2008

This study deals with the development of PMSM(Permanent Magnet Synchronous Motor) for automotive EDC(Electric Drive Compressor). We have already developed the previous version of PMSM. It showed the characteristics of small size and high efficiency. But noise and vibration levels were higher than target values, so it was impossible to apply. So, in order to reduce noise and vibration levels, many parameters like the numbers of slots, the numbers of winding turns, and slot open width were changed. As a result, noise level of newly developed PMSM was decreased about 36.9% at maximum operating frequency (8600 rpm), and was reduced about 37.7% at rated frequency (6000 rpm) with the same sized and more efficient PMSM.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.997-1002
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• 2004

Rumbling sound is one of the most important interior sound of a passenger car. The conventional rumbling noise research was focused on the reduction of the A-weighted sound pressure level. However A-weighted sound pressure level can not give the whole story about the rumbling sound of a passenger car. In this paper, we employed sound metric which is the subjective parameter used in psycoacoustics. According to recent research results, the relation between sound metrics and subjective evaluation is very complex and has nonlinear characteristics. In order to estimate this nonlinear relationship, artificial neural network theory has been applied to derivation of sound quality index for rumbling sound of a passenger car.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.476-481
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• 2013

Transfer path analysis(TPA) and operational deflection shape(ODS) have been widely utilized to analyze the characteristics of noise. TPA enables to decompose a noise into air-borne and structure-borne noises then estimate the path contribution of noise. ODS enables to analyze a moving shape and direction of interest components at a particular frequency. In this paper, TPA and ODS are applied to transfer paths of air-conditioner booming noise in a vehicle to reduce noise level, then a fixture is mounted it's path for distributing the high portion path contribution to the low portion path contribution. Through this experiment, the reduction of sound pressure level in air-conditioner booming noise is observed. Thereafter, TPA is again employed to verify the results of contribution.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.6
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• pp.445-451
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• 2003

Booming sound is one of the most important interior sound of a passenger car. The conventional booming noise research was focused on the reduction of the A-weighted sound pressure level. However A-weighted sound pressure level cannot give the whole story about the booming sound of a passenger car. In this paper, we employed sound metrics, which are the subjective parameters, used in psycoacoustics. According to recent research results. the relation between sound metrics and subjective evaluation is very complex and has nonlinear characteristics. In order to estimate this nonlinear relationship, artificial neural network theory has been applied to derivation of sound quality index for booming sound of a passenger car.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.521-524
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• 2005

To protect a satellite and electronic equipment from the acoustic loads generated by rocket propulsion system, many launch vehicle use acoustic blanket. Most high frequency region of the acoustic loads is reduced by nose fairing skins and acoustic barrier, but low frequency region is not. In order to control low frequency acoustic mode, we designed away resonator panel which was made of composite materials. This paper shows the absorption coefficient measurement result of resonator and SPL(Sound Pressure Level) reduction by using resonators in a rectangular cavity for experiment. Proper arrangement of acoustic resonators at each mode reduce effectively SPL around the satellite through changing boundary condition.