• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11b
• /
• pp.541-546
• /
• 2002

Railway noise is one of the main causes of environmental impact. Whenever a new railway line is planned or a housing project near an existing railway is proposed, an estimate of the relevant levels is usually required. For this, it is necessary to quantify those parameters that affect the railway noise. Therefore we investigated the noise and vibration level which 107 high speed trains generated passing through the block of test railway track between Chunan and Chungwon. This paper presents the status and characteristics of the high speed railway noise and an accurate prediction of the high speed railway noise.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.24 no.4
• /
• pp.332-338
• /
• 2014

Experimental study is conducted for investigating the characteristics of friction-induced noise with respect to the variation of system geometry. In this study, a vertically fixed rod is in contact with the reciprocating plate which is controlled by the step motor. Friction noise is generated during the reciprocating motion due to the frictional contact between the plastic pin and the aluminum plate. The frequencies of the friction noise are changed when the height of the rod varies. However, it is found that the vibration modes involved in the friction noise are not changed. It implies that the unstable modes remain unstable regardless of the change of the system geometry, and thus, there are the certain mode shapes which are likely to produce friction noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11a
• /
• pp.356.2-356
• /
• 2002

Railway noise is one of the main causes of environmental impact. Whenever a new railway line is planned or a housing project near an existing railway is proposed, an estimate of the relevant levels is usually required. For this, it is necessary to quantify those parameters that affect the railway noise. Therefore we investigated the noise and vibration level which 107 high speed trains generated passing through the block of test railway track between Chunan and Chungwon. This paper presents the status and characteristics of the high speed railway noise and an accurate prediction of the high speed railway noise.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.19 no.9
• /
• pp.928-934
• /
• 2009

Underwater impulsive sound such as underwater blasting noise, piling noise and stone breaking hammer affects marine animal hearing response and organs. This study describes the characteristics of various impulsive noise from waterfront construction site and their effect on fish. Time constant, peak pressure, energy and SEL(sound exposure level) of four different underwater impulsive sounds are quantified. Auditory and non-auditory tissue damage ranges are derived by comparing their quantities to the exposure criteria for fish. Damage ranges of auditory tissue and non-auditory tissue of underwater boring blast of 150 kg of charge, are about 100 m and 300 m, respectively. Other three impulsive sounds also gives damage effects but less than that of underwater boring blast.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2013.04a
• /
• pp.644-647
• /
• 2013

The important source of noise from railways is rolling noise caused by wheel and rail vibrations induced by acoustic roughness at the wheel-rail contact. The main contributors for rolling noise are the sleepers, rail and wheels. In order to analyze and predict rolling noise, it is necessary to understand the vibrating behaviors of railway tracks, as well as the wheels. In the present paper, theoretical modelings of the railway track are reviewed in terms of the rolling noise, and they are applied for the three representative types of domestic railway tracks operated: the conventional ballasted track, KTX ballasted track and KTX concrete track. The characteristics of waves propagating along rails were investigated and compared between the tracks. The tracks were modeled as discretely supported Timoshenko beams and compared in terms of the averaged squared amplitude of velocity which is directly related to the sound radiation from the rails.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.05a
• /
• pp.790-795
• /
• 2002

The object of this research is limited to the reduction of compression process noise only among the main sources of compressor noise such as motor noise, compression process noise, and valve port flow noise. Thus the research is focused on the wave motion rather than the particle motion of sound wave travels. A muffler is a commonly used device to reduce the compression process noise, generated by the pressure pulsations caused by the cyclic compression process. In this research, the acoustic characteristics of the muffler are analyzed by using the normal gradient integral equation proposed by Wu and Wan. Moreover, a commercial code SYSNOISE developed by indirect variational boundary integral equation is also used to validate the results. For the noise reduction, the topology optimization technique using a genetic algorithm is used. The number, size and position of the muffler holes are considered as design variables. Compared with original design, the optimized design has very improved acoustic characteristics. Both numerical and experimental analyses are used to evaluate new design.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.24 no.12
• /
• pp.954-961
• /
• 2014

Brake squeal noise of KTX is very uncomfortable to passengers and workers in stations. A lot of study has been conducted to inquire into the mechanism of the squeal noise. But understanding of the brake squeal noise is still challenging. In this study, we developed a full-scale tester equipped with a KTX mechanical brake unit. And we measured the vibrational characteristics of each component of the brake unit and compared them with frequency response functions of brake squeal noise measured also in the tester. It was found that the brake squeal noise was more closely related to the vibrational characteristics of the brake pads and hangers in friction condition than those of free components.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.796-799
• /
• 2014

It is treated more seriously than ever as the customer requirements are becoming a high-quality and diversification. Among the various elements to affect customer's evaluation of automobile quality, BSR(buzz, squeak, rattle noise) are considered to be a mostly contributing factor. Rattle Noises in cockpit modules are one of the major concerns mentioned above. Recently, measurements of the BSR noise between the parts that make up the products from the perspective that the structural causes. For structures that make up material has not been any consideration of the BSR noise characteristics. The aim of this study is to clarify the characteristics of noise occurrence in vehicle cockpit module that consist of plastic material after measuring noise by rattle special testing instrument.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2012.10a
• /
• pp.568-574
• /
• 2012

Turbulent boundary layer noise is already a significant contributor to sonar self noise. For developing acoustic window of sonar system to reduce self noise, a parametric study of design factors of acoustic window is presented. Distance of sensor array from acoustic window, material and damping layer are studied as design factors to influence in the characteristics of the transfer function of self noise. As the result these design factors make change the characteristics of transfer function slightly. Among design factors the location of sensor array is most important parameter in the self noise reduction.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.9
• /
• pp.1475-1482
• /
• 2001

Nowadays reduction of gear noise in power transmission is very important, because the noise regulation is severe and demand of customer on noise is increased. To reduce gear noise, it is necessary to understand the noise characteristics of helical gear. In this work, we designed test rig for the study of gear noise and installed in semi-anechoic chamber. By using this rig, sound pressure level is measured under varying rotational speed and torque. The frequency characteristics of helical gear noise on the effect of lead errors and torque are discussed.