• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.26 no.3
• /
• pp.103-107
• /
• 2014

To assess a various of workplace noise environment in the tunnel construction site, the measurement is performed while tunnel constructing work. This study focuses on the sound attenuation according to the sound frequency characteristics and the distance from various works in the tunnel. Also, the noise distribution while blasting work is measured according to distance in this study. In addition, the boring processing, muck treatment, and tunnel lining by distance are measured for the noise distributions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.05a
• /
• pp.300-303
• /
• 2004

In this paper, floor impact noise reduction in a cruise ship cabin by using floating floor is studied. A mock-up is built by using 61 steel plate, and two identical cabins are made where 25t panel is used to construct wall and ceiling inside the steel structure. Various floating floor systems are tested for which normalized impact noise is measured according to ISO 140-7 It is shown that effect of VL(Visco-elastic Layer) is negligible when it is used between deck and mineral wool, since most vibration absorption occurs in the wool. In addition, direction of the mineral wool fiber affects impact noise significantly.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.1865-1870
• /
• 2000

Sound propagation along the surface of the ground can be affected by the roughness of the ground surface and the direction of the wind. Noise Source parameter and ground factor are estimated using the measured results of two points under particular environmental condition, and the noise level of arbitrary points under the same environmental condition can be estimated. The results can be used for the prediction of the noise level from a source above a plain and homogeneous ground surface with no obstacles nearby. Upward and downward conditions are also addressed in addition to ground effect. The proposed method can be utilized to estimate the noise level of specific noise environment and its validity was confirmed with the results of actual field measurement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.751-755
• /
• 2003

In this paper, floor impact noise reduction in a steel structure is studied. A mock-up is built by using 6t steel plate, and two identical cabins are made where 25t panel is used to construct wall and ceiling inside the steel structure. Various floating floor systems are tested for which normalized impact noise is measured according to ISO 140-7. In addition, floor SBN(Structure-borne Noise) and floor damping are measured to study the effect of floating floor. structure. It is shown that VL(Visco-elastic Layer) is more effective when hard plates are added above the VL.

• Journal of the Society of Naval Architects of Korea
• /
• v.41 no.5
• /
• pp.41-47
• /
• 2004

In this paper, floor impact noise reduction in cruise ship cabin is studied. A mock-up is built by using 6t steel plate, and two identical cabins are made where 25t panel is used to construct wall and ceiling inside the steel structure. Various floating floor systems are tested for which normalized impact noise is measured according to ISO 140-7. In addition, floor SBN (Structure-borne Noise) and floor damping are measured to study the effect of floating floor structure. It is shown that VL(Visco-elastic Layer) is more effective when hard plates are added above the VL.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2012.10a
• /
• pp.153-158
• /
• 2012

Noise maps are produced according to 'The Method of making a Noise Map' in order to noise control efficiently, and prediction model to predict road traffic noise which may apply to Korean situation, include CRTN, RLS 90, NMPB, Nord 2000 and ASJ 2003. Of them, ASJ 2003, Japan's prediction model has not been verified for the application to Korean situation according to the classification of vehicle. In addition, ASJ 2003 was revised to ASJ 2008 recently, a classification for motorcycle was added. This study attempts to check the classification of vehicle in ASJ 2008 and 'The Method of making a Noise Map' to confirm the suitability of the application of them to Korean situation.

• Proceedings of the KSR Conference
• /
• 2008.06a
• /
• pp.1834-1839
• /
• 2008

The construction of concrete slab track system is increased because the system has advantages which are maintenance free and so on, the other side, the system has weak points such as increase of the cost of the early stage construction. Recently, railway environment is issued including noise. Therefore, measures which are to mitigate noise on slab tracks were introduced, however, it is found that efficiency of noise reduction is low because noise problem is still issued. In this study, to grasp noise characteristics on slab tracks we measured noise on high speed rail slab track in addition Saemaul and Moogungwha and the results have done comparative analysis.

• Journal of Institute of Control, Robotics and Systems
• /
• v.13 no.6
• /
• pp.547-554
• /
• 2007

This thesis presents a kind of active noise control(ANC) algorithm for reducing noise due to engine inside a car. The proposed control algorithm is, by using WP(Wavelet Packet), a one improving the instability due to delay of noise transmission and the lack of response ability for the rapid change of noise, which are defects of the existing FXLMS(Filtered-X Least Mean Square) algorithm. The chief character of this system is a thing that faster operation than the FXLMS is implemented by inserting WP in the secondary path. In other words, WP implements parallel operation. Then, the weights of filter in the adaptive algorithm will be updated faster. In addition, because WP have so excellent a resolution, they can process very minute noise. The efficiency of this control algorithm will be demonstrated in the matlab simulation and in the actual experiments by using a Labview program and a car.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.11a
• /
• pp.513-516
• /
• 2004

Consistency in design, manufacture, installation and performance test of expansion joints is insufficient for guarantee of reliability because they are imported from various foreign countries as America, Japan and Europe. In addition to that, the regulations or codes of expansion joint should be revised and established for levels of vibration and noise generated from riding vehicles especially. Regulation on the noise neighboring traffic roads is established by ministry of environment. Therefore, Field tests on the vibration and the noise at expansion Joints, especially rail-type and finger-type joints which are typical ones in bridge with short or middle span, are performed and performance of expansion joints are analyzed. And so, the results of the investigation will be utilized as basic data for the regulation on the vibration and the noise.

• Journal of the Korean Society of Visualization
• /
• v.21 no.3
• /
• pp.39-48
• /
• 2023

In this study, we investigate the effects of slots installed on the tip of a rotor blade on aerodynamic characteristics. The slots weaken the strength and spatial coherence of the tip vortex at early vortex age and accelerate the dissipation of the generated tip vortex. Accordingly, the turbulence intensity of the rotor wake is reduced at both near and far wake, which leads to a reduction in broadband noise. Tonal noise is also reduced by mitigation of tip vortices, but tonal noise reduction is limited to a narrower range of azimuths than broadband noise due to the extinction of tip vortices. In addition, slots reduce both mean thrust and thrust fluctuations. Reduction in thrust fluctuations leads to a reduction in blade loading noise, resulting in a reduction in tonal noise.