• International Journal of Highway Engineering
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• v.18 no.5
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• pp.49-56
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• 2016

PURPOSES : In this study, noise reduction effect of a two-layer porous asphalt pavement was investigated through site measurement and computer simulation. METHODS : To examine noise reduction effect, a 3 km long quiet pavement was installed by removing previous normal pavement, which had a rather low porosity. The studied site was a high-rise apartment building surrounded by the quiet pavement and Seoul ring road with heavy traffic volume, indicating relatively high background noise. RESULTS : The measurement result before and after installing the quiet pavement showed a noise reduction effect of 4.3 dB(A) at a distance of 7.5 m from the road. After validating the accuracy of simulation using SoundPLAN, the reduction in SPL(sound pressure level) at the facades by the quiet pavement was predicted by considering five different road conditions generating traffic noise from each road or in the combination of the quiet pavement and Seoul ring road. In the case of no noise from Seoul ring road, noise reduction at the facades was 4.2 dB(A) on average for 702 housing units. With background noise from Seoul ring road, however, the average SPL decreased to 2.0 dB(A). Regarding subjective response of noise, the number of housing units with a noise reduction of over 3 dB(A) was 229 out of 706 units (approximately 32%). For 77 housing units, the noise reduction was between 1~3 dB(A), while it was less than 1 dB(A) for 400 housing units. CONCLUSIONS : The overall result indicates that the quiet pavement is useful to reduce noise evenly at low and high floors compared to noise barriers, especially in the urban situation where background noise is low.

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

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.9
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• pp.791-796
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• 2010

Installing noise barriers is the most common method for reducing the highway traffic noise to the road side residential area. After the report about edge potential concept of a noise barrier, various types of noise reducing devices(NRDs) called "noise reducers" have been suggested for getting more shielding effect on the top of highway noise barriers. But, it has been doubtful about effect of the NRDs in field because there was no appropriate and unified method to estimate the acoustic performance by using field measurement of the NRDs in Korea. In this study, the authors have considered to setup a practical method to test and estimate the acoustic performance of NRDs. For eliminating the noise reduction effect of the NRDs height itself, the source and measuring points are adjusted as highly as the NRDs height. For the frequency weighting in the estimation of the NRDs effect, the highway noise spectra were measured at asphalt and concrete road side and then averaged for a unit spectral parameter.

• Journal of KSNVE
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• v.10 no.4
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• pp.629-635
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• 2000

Wheel /rail interaction has been known as a major source of railway noise. In this paper, a low noise wheel structure is developed and its effect on noise reduction is investigated. The developed low noise wheel employees a rubber material inserted into a steel rim or mounted on the wheel surface. Since the low noise wheel has low stiffness and high damping ratio compared to a solid wheel, the measurement results show that it reduces the rolling and squeal noise. It turns out that the proposed wheel could reduce interior noise level by 4∼5dB(A) and vehicle vibration level by 7∼10 dB. Although the proposed structure seems to be promising in noise reduction of railway vehicles, the low noise wheel is to be verified in endurance and cost effect.

• Journal of Environmental Science International
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• v.24 no.5
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• pp.647-655
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• 2015

In this study, to targeting Songpa of Seoul, were analyzed the effect on the noise mitigation in roadside buffer green spaces. Noise of Songpa Street buffer green space was determined to be higher during the day than at night. In addition, it was most of 60 db or more. However, the noise reduction function of the buffer green was not greatly affected by time. In the case of noise reduction rate, during the day time it was the order of the mounding type (18.14%)> plain type (5.73%)> slope type (4.08%), And, in the case of night time, it was the order of the mounding type (11.29%)> slope type (10.22%)> plain type (4.42%). Noise reduction rate, all of the daytime, was the highest in the mounding type. As a result of the factors on the amount of reduction of noise, More physical structure is mounding type, green structure is the stratification of green space, and the number of individuals is large, the higher the tree planting density, it is determined that the noise reduction effect is high. Also, factors affecting the noise reduction effect of the day and night were different.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1177-1182
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• 2007

This study aims at identifying the effect of preferred visual and auditory stimuli on the road traffic noise perception through the series of psychoacoustic experiments. The first experiment was designed to find the addition effect of a sound reproducing system in a square where lay adjacent to roads with road traffic noise, provide appropriate music corresponding to the varying conditions of weather in the given space. In result, it was found that the rating around the square improved toward more positive adjectives. The second experiment was designed to assess the visual effect of twelve roadsides with different landscapes on the road traffic noise perception. As a result, approx. 3 to 5 dB(A) of psychological reduction was seen in places where natural landscape was preferred, compared to the others, although the noise levels were similar. The third experiment was designed to evaluate the effect of visual screen from adjacent roads on road traffic noise perception by means of ME method in a laboratory. In result, the effect of psychological reduction was observed at 65dB(A) or lower. Especially, complete screening from adjacent roads led to 5 to 10% of loudness reduction effect, compared to non-screening cases. Finally, the fourth experiment was designed to evaluate the effect of visual and auditory information with ME method and 7-point SD rating scale in a laboratory. In result, up to 10% of loudness reduction and about 2dB(A) of noise perceptional reduction were seen at 65dB(A) or lower.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.11
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• pp.1222-1230
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• 2009

A theoretical model was developed to compute the effect of a bubble layer in reducing the radiation noise generated by a force applied on an infinite flat plate considering the noise of multi-bubbles. Using the model, the effectiveness of a bubble layer in reducing the structure-borne noise of the plate was evaluated to consider various parameters such as the source noise levels, the thickness of bubble layers, the volume fractions and the frequency characteristics of bubbly fluids. Considering the noise of multi-bubbles, the actual reduction effect of radiation noise using a bubble layer was expected in cases of high source levels, high volume fractions of bubbles and large thickness of the bubble layer above the resonance frequency of the bubble layer. Accordingly, it is recommended that the thickness of a bubble layer, the source noise level and the characteristics of bubbly fluids should be optimized cautiously to maximize noise reduction effects.

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

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1049-1052
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• 2006

Object of this study is to develop an Stack Silencer System for quieting abnormal noise around power plant. Abnormal noise gets resident people to feel uncomfortable. Stack Silencer System is to minimize pressure loss of exhaust gas and to maximize noise reduction effect from abnormal noise frequency band. Stack Silencer System is installation in stack and absorbing material is an aluminum foam. Reduction effect measures insertion loss of $8.2{\sim}19.4dB$ by Stack silencer installation. After Stack Silencer System installation, pressure loss of exhaust gas measured $5{\sim}9mmH_2O$.

• Proceedings of the IEEK Conference
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• 2000.06d
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• pp.234-237
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• 2000

A number of theoretical researches have been done in recent years on the restoration of images and a variety of algorithms have been developed to implement noise reduction methods. However the blurring effect has not been perfectly overcome in the process of noise reduction. In this paper, we propose a new approach to image restoration that the blurring effect is significantly decreased and the performance of the noise reduction improves by eliminating the noise in the wavelet transform domain in comparison with the conventional noise reduction methods. The proposed algorithm performs much better than the conventional in the subjective image quality and PSNR performance. It is verified through computer simulations,