• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.923-927
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• 2003

The aim of this study is to investigate the characteristics and quantity of the noise reduction by pipe material, wrapped pipe with glass wool and installed pipe height The characteristics of noise emission from drain-pipes is as follows. The noise reduction pipe in PVC can reduce noise levels in 7-10㏈ and the cast-iron pipe can reduce in 14㏈compared with the normal PVC pipe. In these days, the glass wool was used for preventing the burst and the noise reduction. But the glass wool for wrapping pipe is not effective to the noise reduction. The characteristics of noise emission from various installed pipe height were measured As the ceiling space of the remodeled building was raised, the noise level was troubled by increasing of the vertical pipe length.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1273-1279
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• 2000

A new concept of piezoelectric smart panels for noise reduction in wide band frequencies is proposed and their possibility is experimentally investigated. The proposed panels are based on active and passive methods. They use piezoelectric smart structure technology for active noise reduction at low band frequencies and passive sound absorbing materials for mid-range of noise frequencies. To prove the concept of piezoelectric smart panels, an acoustic measurement experiment was performed. The smart panels exhibit a good noise reduction in middle and high frequency ranges due to the mass effects of absorbing materials or/and the air gap. The use of piezoelectric smart panel renders noise reduction large at resonance frequency. Another concept of smart panel that uses piezoelectric damping is experimentally investigated. Since piezoelectric dampings can reduce vibration and noise at resonance frequencies with simple shunt circuit, they have merits in terms of economy and simplicity. Dissipated energy method(DEM) is adopted to tune the shunt circuit precisely in piezoelectric dampings. Noise reduction at multiple resonance frequencies is demonstrated.

• Journal of Ocean Engineering and Technology
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• v.25 no.2
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• pp.1-6
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• 2011

Vibration-based Structural Health Monitoring (SHM) systems use field measurements of operational signals, which are distorted by noise from many sources. Reducing this noise allows a more accurate assessment of the original "clean" signal and improves analysis results. The implementation of a noise reduction methodology for the Modal Distribution Method (MDM) is reported here. The spectral subtraction method is a popular broadband noise reduction technique used in speech signal processing. Its basic principle is to subtract the magnitude of the noise from the total noisy signal in the frequency domain. The underlying assumption of the method is that noise is additive and uncorrelated with the signal. In speech signal processing, noise can be measured when there is no signal. In the MDM, however, the magnitude of the noise profile can be estimated only from the magnitude of the Power Spectral Density (PSD) at higher frequencies than the frequency range of the true signal associated with structural vibrations under the additional assumption of white noise. The implementation of the spectral subtraction method to MDM may decrease the energy of the individual mode. In this work, a modification of the spectral subtraction method is introduced that enables the conservation of the energies of individual modes. The main difference is that any (negative) bars with a height below zero after subtraction are set to the absolute value of their height. Both noise reduction methods are implemented in the MDM, and an application example is presented that demonstrates its effectiveness when used with a signal corrupted by noise.

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.149-152
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• 2003

This paper presents a method to find motion vectors that are closer to true motion with noisy images for simultaneous noise reduction and do-interlacing. The proposed method requires four interlaced field images: one noisy field image and three field images from which noise is already removed. The validation of motion provides accurate motion vectors and allows us to utilize them even in very noisy environment. The validated motion vectors are first used for the noise reduction, buffered and used later for the noise reduction and de -interlacing.

• The Korean Journal of Applied Statistics
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• v.24 no.5
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• pp.905-914
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• 2011

In the field of image processing, the removal noise contamination from the original image is essential. However, due to various reasons, the occurrence of the noise is practically impossible to prevent completely. Thus, the reduction of the noise contained in images remains important. In this study, we estimate the level of noise variance based on the measurement of the relative strength of the noise, and we propose a noise reduction algorithm that uses a sigma filter. As a result, the proposed statistical noise reduction methodology provides significantly improved results over the usual sigma filtering regardless of the level of the noise variance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.125-130
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• 2014

High speed railroad car and high-rise apartment with development of railway technology cause different problems of noise contrary to the previous generation. It is the most efficient noise reduction countermeasure but we studied that is the way on noise propagation with sound proof wall or sound proof tunnel around railroad. But if it were railroad on bridge, additional cost which is more expensive than installing one on the ground is needed. So sound insulation material considering reducing weight of recent soundproof facilities must be selected. It is in this study that predicted and analyzed acoustical and structural effect for noise reduction by installing soundproof tunnel. If it were departmentalized into additional study, could be able to expect noise reduction effect of sound proof tunnel establishment on the bridge.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.146-151
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• 2002

The object of this study is an examination of source of robot noise and reduction of the noise and the vibration for an industrial robot system. As the first step in our study, the noise and the vibration from the robot are measured by microphones and by accelerometers and the source of the noise and the vibration are proved to be from the gear, shaft, and housing from the experiments. The occurrence of the noise may be classified according into kinds, Finally base on the result of the experiments, we consider a countermeasure for reducing the noise and the vibration of robot system by the parametric study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.321.1-321
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• 2002

The object of this study is an examination of source of robot noise and reduction of the noise and the vibration for an industrial robot system. As the frist step in our study, the noise and the vibration from the robot are measured by microphones and by accelerometers and the source of the noise and the vibration are proved to be from the gear, shaft, and housing from the experiments. The occurrence of the noise may be classified according into kinds, Finally base on the result of the experiments, we consider a countermeasure fur reducing the noise and the vibration of robot system by the parametric study.

• 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 KSR Conference
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• 2011.10a
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• pp.663-669
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• 2011

Since railway vehicle's improvements on speed and weight has caused interior noise, the passenger's convenience fell dramatically. Therefore many on-going researches are dedicated to reduce interior noise. In this study the analytical prediction of interior noise reduction has done through filling up the empty space using form and to modify the floor structure, which contributes highly with interior noises. Using Statistical Energy Analysis(SEA), the interior noise of the vehicles without the form filling on the floor structure and the vehicles with form filling and also a modified structure has been predicted. The selected percentage of form filling was 0, 50, 100% and through this research the analysis of noise reduction by form filling has been made. When floor structure has been filled with form, approximately 2 dB of noise reduction was observed and the difference of noise reduction level with 50 and 100% form filling was predicted to be very little. Through this study, the expectation of interior noise reduction in high speed trains is considered high.