• Journal of Environmental Health Sciences
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• v.34 no.4
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• pp.311-315
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• 2008

This study was performed to investigate propagation characteristics and effects of road traffic noise generated from vehicles. Noise levels of expressway and general road were measured at four points in a straight line based on distance from the road, and analyzed. The average noise level of expressway was 78.9 dBA at 5 m, 76.4 dBA at 10 m, 72.0 dBA at 20 m, 69.0 dBA at 30 m. That of general road was lower about $3.1{\sim}3.5\;dBA$ than that of expressway. There was no significant difference in distance attenuation between expressway noise and general road noise. The farer the distance from source is, the more the attenuation is. The influence range of noise is assessed by noise environmental standards or road noise limits. Noise levels of the time zone were measured at a boundary line of apartment to grasp noise variation by time. The time zone of lowest noises was $3{\sim}4$ a.m. and that of highest noise was $8{\sim}10$ a.m. Data recorded on tapes were analyzed to understand the characteristics of frequency because these characteristics are important factors to plan the noise reduction measures, namely path measures.

• Nuclear Engineering and Technology
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• v.41 no.10
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• pp.1315-1322
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• 2009

The present article is concerned with the application of an electrochemical noise (EN) monitoring technique to analyze the initiation and propagation of Pb-assisted stress corrosion cracking (SCC) of an Alloy 600 material in a simulated environment of a steam generator (SG) sludge pile at high temperatures. A typical increase of electrochemical current noise (ECN) and electrochemical potential noise (EPN) was frequently recorded from the EN measurement in a caustic solution with such impurities as PbO and CuO, indicating that there are localized corrosion events occurring. With the aid of microscopic and spectral analyses, the EN data involving information on such stochastic processes as uniform corrosion and the initiation and propagation of SCC, were analyzed based on a stochastic theory.

• Journal of Environmental Science International
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• v.16 no.7
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• pp.771-778
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• 2007

This study has been conducted to achieve the following objectives: First, in order to understand the horizontal propagation and attenuation characteristics for the railroad traffic noise, we selected areas within 100 meters away from the railroad and then selected Saemaul-ho and Mugoongwha-ho as the subjects for our experiment. In this way, we analyzed the horizontal propagation and attenuation characteristics for the traffic noise occurring in diversified areas. Second, in order to understand the vertical propagation and attenuation characteristics for the railroad traffic noise, we measured and analyzed the distributional characteristics of vertical sound pressure levels on each floor of multi-storied apartment buildings according to changes of traffic load and types, and the existence or nonexistence of soundproof walls. For the case of the railroad traffic noise, we also selected Samaul-ho and Mugoongwha-ho as the subjects for our experiment, and we measured and analyzed the different noise levels on each floor of multi-storied apartment buildings from the soundproof wall. The results of Horizontal propagation and attenuation characteristics for the railroad traffic noise are as follows: In cases of the flat land, cutting land, and bridge area, as distance increases, the sound pressure level steadily decreases. The sound pressure level for the bridge area is higher than that of the flat land with a measurement of $5.5{\sim}10.2\;dB(A)$. Vertical propagation and attenuation characteristics for the railroad traffic noise are as follows: The amount of sound pressure level decrease is $14.2{\sim}14.8\;dB(A)$ for Samaul-ho and $13.5{\sim}14.3\;dB(A)$ for Mugoongwha-ho when measuring the vertical sound pressure levels at heights lower than 4.5 m, which indicates a fairly large decrease. At 6 m, the amount of decrease is 8.6 dB(A) for Samaul-ho and 8.2 dB(A) for Mugoongwha-ho, which indicates a small decrease.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1237-1240
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• 2007

Tire noise is a major noise source at high speeds. One of the noise source is controlled by pattern and structure. Pattern noise is effected by the shape of tread. And the bending stiffness of tire is influenced to the resonance of tire‘s belt. But in high frequency region, FEA is not appropriated with application. So this paper discusses about wave propagation of tire. There has been much effort to verify the flexural wave velocity with structure design specification.

• Journal of the Korean Society for Railway
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• v.5 no.1
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• pp.26-31
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• 2002

The more sophisticated patterns of propagation model is presented in this paper, which includes three different source characteristics (spherical, cosine and dipole). The spherical, cosine and dipole radiation characteristics compared, and sound event level and the maximum sound level are calculated by experiment and calculation. It is shown that patterns of propagation have dipole characteristics for low speed range (below about 150Km/h) at electric multiple system. We know that push-pull high speed system has cosine characteristics of noise propagation at low speed range (below about 200Km/h).

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.204-209
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• 2001

The more sophisticated patterns of propagation model is presented in this paper, which includes three different source characteristics (spherical, cosine and dipole). The spherical, cosine and dipole radiation characteristics compared, and sound event level and the maximum sound level are calculated by experiment and calculation. It is shown that patterns of propagation have dipole characteristics for low speed range (below about 150Km/h) at electric multiple system. We know that push-pull high speed system has cosine characteristics of noise propagation at low speed range (below about 200Km/h).

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.303-310
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• 2008

In Korea, the current noise impact assessment has not yet considered the vertical noise propagation property by buildings and other obstacles. And noise control plan has been established without conducting the economic assessment for the noise control facilities. A noise map is used to calculate the noise level based on a theoretical formula or an empirical formula, and also predict the characteristics of vertical propagation by linking with a geometry data. And It is Possible to analyze cost-effect of noise control facilities by consider installation costs. In this study, we addressed the application of noise map for noise impact assessment and cost-effect analysis of noise control facilities.

• Corrosion Science and Technology
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• v.9 no.2
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• pp.57-66
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• 2010

Since nuclear power plants are being operated under high temperature and high pressure, on-line monitoring technique to detect corrosion could be more effective than off-line method in shut-off period. In this operating condition, electrochemical noise method may be suitable to monitor the corrosion. This paper aims the analysis on the relation between the cracking and electrochemical noise signal of Alloy 600 under U-bending. When electrochemical noise monitoring technique was used during SCC test, it was judge to be obvious that if cracks generate, its generation can be detected by electrochemical current noise. Cracking-related noise was defined as the noise showing 5~10 times greater than the average value of background noise bands. On the base of crack noise, crack initiation time was determined. From SCC test and electrochemical noise monitoring in $25^{\circ}C$, 0.1 M $Na_2S_4O_6$ solution (Reverse U-Bended Alloy 600 SE+), average crack initiation time was obtained as 9,046 seconds and from its initiation time, it could be defined that net crack propagation rate is the crack length divided by ${\Delta}T$(= total test period - crack initiation time). Therefore, average net crack propagation rate was obtained to be $1.18{\times}10^{-9}\;m/s$.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.6
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• pp.362-371
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• 2022

As considerable interests in noise emission from the ships have been increased, International Maritime Organization (IMO) standardized the Underwater Radiated Noise (URN) measurement process of commercial ships in deep seas by enacting the related ISO standard ISO 17208-1 and classification societies responded with the enactment or revision of corresponding notations. According to this trend, a new hybrid underwater sound propagation model based on underwater sound propagation theories was developed and its accuracy on analysis was verified through the result comparison with the results of other generally used models. Using the verified model, each URN propagation characteristics adjusted by the correction methods proposed in the ISO standard and class notations were analyzed and compared in two assumed URN measurement cases. The results showed that the effects of transmission loss corrections in the circumstances with less bottom reflections generally similar but they had rather large differences in the model analysis results with bottom-reflection-dominant conditions. It was concluded that the deep consideration of effective bottom-reflection-correction method should be made in future revisions of ISO standard and class notations.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2265-2271
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• 1994

With the improvement of standard of living, requirement for comfortable and quiet environment has been increased and, therefore, there has been a many researches for active noise reduction to overcome the limit of passive control method. In this study, active noise control is performed in a duct system using intelligent control technique which needs not decide the coefficients of high order filter and the mathematical modeling of a system. Back propagation algorithm is applied as an intelligent control technique and control system is organized to exclude the error microphone and high speed operational device which are indispensable for conventional active noise control techniques. Furthermore, learning is performed by organizing acoustic feedback model, and the effect of the proposed control technique is verified via computer simulation and experiment of active noise control in a duct system.