• International Journal of Highway Engineering
• /
• v.19 no.6
• /
• pp.1-11
• /
• 2017

PURPOSES : The purpose of this study is to compare noise reduction quantities between before/after two-layer low noise pavement implementation using equivalent noise level analysis and to analyze the noise reduction effects of the two layer low noise pavement with a statistical method such as the Anderson-Darling Test. METHODS : In order to compare and to analyze noise reduction effects between before/after two-layer low noise pavement implementation, data acquisition as noise levels on a roadside and an apartment rooftop was conducted in the study area. The equivalent noise level was estimated in order to compare noise reduction quantities and the Anderson-Darling Test was carried out for estimating noise reduction effects of the two-layer low noise pavement. RESULTS : The equivalent noise levels of before/after two-layer low noise pavement implementation for the roadside during the daytime are 65.355 dB and 63.520 dB and during the nighttime are 62.463 dB and 59.088 dB. The equivalent noise levels for the apartment rooftop during daytime are 57.301 dB and 59.088 dB and during the nighttime are 54.616 dB and 52.464 dB. Also two-layer low noise pavement decreased the noise reduction effects estimated with the statistical method as the Anderson-Darling test for the roadside during the daytime by around 66.68% and decreased noise reduction effects on the roadside during the nighttime by 0.70%. Moreover it reduced noise reduction effects in the apartment rooftop during the daytime and nighttime by 0% and 96.32%, respectively. CONCLUSIONS : Based on the result of this study, two-layer low noise pavement can positively affect noise reduction during both the daytime and nighttime according to the results of estimating the equivalent noise levels and the Anderson-Darling test.

• Proceedings of the KSR Conference
• /
• 2008.11b
• /
• pp.125-131
• /
• 2008

This research tries to analyze and investigate the effects of the noise reduction test for the sound-absorbing materials installed tentatively on Metro Line 5. Though the noise reduction effects of each sound-absorbing material showed that there was about $2{\sim}5\;dB$ compared with before and after of the tentative installation, it shows that the noise reduction effects are reducing because of the section change condition such as dust absorption and the rail abrasion as time passes after the tentative installation. Also, many difficulties are occurring in the maintenance of the orbit facilities because of the installation of sound-absorbing materials. Though various abroad products for noise reduction are imported like this, the researches for the noise reduction effect increase for this and the improvement direction are being required because of the poor circumstance of the efficiency aspect compared to the economic investment effect because those are not suited to the character of domestic Metro.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.27 no.1
• /
• pp.57-64
• /
• 2017

This study was reviewed the noise reduction effects with installation of 'point to point speed camera' for controlling the speed of the car. The multiple regression analysis was performed to know how the relationship between the noise level and these parameters, such as measured traffic volume and rate of heavy vehicle and weighted average speed was changed with and without the 'point to point speed camera'. In the analysis results shows that the less traffic volume, the more noise reduction effect has been increased and the more traffic volume, the more noise reduction effect has been reduced. And noise reduction effects by the 'point to point speed camera' was different from each measured point. The cause of the difference was determined that inadequate 'point to point speed camera' position to see the effect of noise reduction. It is determined to require a more study to improve the noise reduction effects of the 'point to point speed camera' such as the camera position adjustment.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.32 no.5
• /
• pp.35-42
• /
• 2004

This study examines the traffic noise reduction effects of the diverse efficiency features of a sunken square, and investigates the reduction effects and characteristics of noise alterations according to the construction conditions in order to verify its possibility as a new noise reduction facility. The measured data were analyzed. As a result, (1) the traffic noise from the roads around the sunken squares exceeded the regulatory standards; (2) the sunken squares were protected from noise; (3) the sunken spaces yielded a greater reduction by 6∼7dB than the flat ground thanks to the diffraction effect; and (4) there were fine changes to noise according to the conditions of space construction. In short, a sunken square has the potential to afford new applications as a noise reduction facility in a highly concentrated downtown with the existing defects solved. In addition, its use for effective noise control is evident based on the noise characteristics of a space. Future studies need to include efforts to provide clearer quantitative data, as well as research on shape, layout, and materials.

• 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.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.13 no.11
• /
• pp.838-844
• /
• 2003

The noise and vibration reduction schemes of an industrial robot are studied. Experimental procedures are employed to examine the sources of robot noise. A parametric study is undertaken to observe the effects of each part such as gear, shaft and housing on the sound pressure level. After the part which mainly effects on the noise is proved, we propose countermeasures for reducing the noise and vibration of the robot system.

• Journal of Environmental Science International
• /
• v.25 no.10
• /
• pp.1407-1415
• /
• 2016

In this study, we investigated the relationship between noise reduction and the community structure of nine groups of typical plant communities as well as the reduction in noise at different frequencies. The semantic differential method was adopted to explore the perception of noise reduction. The results indicated that there was a significantly positive correlation between noise reduction and coverage, a significantly negative correlation between noise reduction and bifurcate height, and a negative correlation between noise reduction and bare rate. However, there was no significant correlation between noise reduction and height, diameter at breast height, or crown width. The reduction of middle-frequency noise was better than that of low- and high-frequency noise. The indicators "quiet" and "calm" showed that plant communities could reduce the noise perceived by humans. However, overly dense woodland caused nervousness, fear, depression, and other negative effects. Relatively open environments and those with large forest gaps obtained the highest evaluation.

• Environmental Engineering Research
• /
• v.20 no.4
• /
• pp.383-391
• /
• 2015

Transparent type noise barrier is a desirable facility since it provides a secure view to drivers and passengers. However, reflection from this type of barrier could annoy dwellers on the sides of the road. To reduce reflection noise by transparent type barrier, modification can be made to the shapes on the front side and hence get effects by distortion of sound transmission. To achieve this, we have conducted simulation by which the effects of patterned screens of noise barrier on high-ways were investigated. The reduction effects of reflected sounds were evaluated for swelling, swelling with curved, rectangular and V-shaped screen type barriers, compared to the planar panel. The emitting noise was generated by 6-lane road and the patterned noise barriers had shown the reduction effects, especially in swelling and swelling with curved type for middle height dwellers, and the V-shaped screen type for higher elevation dweller. The swelling-type showed a decrease of 0.7~1.2 dB, performing the best diminution effect among the tested noise barriers.

• New & Renewable Energy
• /
• v.16 no.2
• /
• pp.1-13
• /
• 2020

The reduction of noise from wind turbines has been studied using various methods. Some examples include controlling wind turbine blades, designing low-noise-emitting wind turbine blades, and using trailing-edge serrations. Among these methods, serration is considered an effective noise reduction method. Various studies have aimed to understand the effects of trailing-edge serration parameters. Most studies, however, have focused on fixed-wing concepts, and few have analyzed noise reduction or developed a prediction method for rotor-type blades. Herein, a noise prediction method, composed of two noise prediction methods for a wind turbine with trailing-edge serrations, is proposed. From the flow information obtained by an in-house program (WINFAS), the noise from non-serrated blades is calculated by turbulent ingestion noise and airfoil self-noise prediction methods. The degree of noise reduction caused by the trailing-edge serrations is predicted in the frequency domain by Lyu's method. The amount of noise reduction is subtracted from the predicted result of the non-serrated blade and the total reduction of the noise from the rotor blades is calculated.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.3
• /
• pp.1143-1151
• /
• 2013

Reasonable methods are needed to predict the noise level of new/existing roads and to select means of noise reduction. In this study, the noise reduction effects of both soundproof walls and quiet pavements were predicted. The noise reduction effects of quiet pavements were predicted by measurement data obtained using the CPX method in test pavements. The noise reduction effect was predicted by KHTN program when applied to soundproof walls and quiet pavement. As a result, the predicted noise level was similar to the measured one. The design method was suggested by an economic analysis using noise benefit of predicted noise reduction. The research suggests that the optimum alternative has to be determined using noise prediction method and life-cycle cost analysis.