• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.12
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• pp.1771-1776
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• 2013

Most cases of power transformer failure are caused by physical factors linked to the transient vibrations of multiple 120Hz combinations. In addition, the noise generated in the transformer from this vibration not only directly contributes to the worsening of the work environment but also causes psychological stress, resulting in the worsening of the workers efficiency and of the living environment of the inhabitants around the power plant. Thus, to remedy these problems, the mechanical-excitation forces working on a power transformer were categorized in this study, and the mechanical-damage mechanism was identified through the vibration transfer paths acting on machines or structures. In addition, a study on active noise cancellation in a transformer using the FXLMS algorithm was conducted to develop a system that is capable of multiple-sound/channel control, which resulted in the active noise reduction effect when applied on the field.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.3
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• pp.171-177
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• 2016

Noise problem that occurs in living environment is a big trouble in the economic, social and environmental aspects. In this paper, the filtered-X LMS algorithms, the adjoint LMS algorithms, and the robust adjoint LMS algorithms will be introduced for applications in active noise control(ANC). The filtered-X LMS algorithms is currently the most popular method for adapting a filter when the filter exits a transfer function in the error path. The adjoint LMS algorithms, that prefilter the error signals instead of divided reference signals in frequency band, is also used for adaptive filter algorithms to reduce the computational burden of multi-channel ANC systems such as the 3D space. To improve performance of the adjoint LMS ANC system, an off-line measured transfer function is connected parallel to the LMS filter. This parallel-fixed filter acts as a noise controller only when the LMS filter is abnormal condition. The superior performance of the proposed system was compared through simulation with the adjoint LMS ANC system when the adaptive filter is in normal and abnormal condition.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.9
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• pp.825-829
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• 2012

The global warming caused the changes of our environment like an increasing tropical night phenomenon in the middle latitude areas. Especially, in Korea, the habitats of tropical Korean blockish cicada have changed from Jeju island located in Southern part of Korea to the whole of Korea because of the increasingly warming weather. The cicadas crying sound have been social problem because the tropical Korean blockish cicadas cry at middle of the night owing to the various outdoor lights. The cicada is positive phototaxis insect. So, the cicada is not cry at night. But if the outdoor light is very bright, then the cicada confuse the night as a day and start to cry. As a result, the cicadas crying noise has caused the resident living in downtown to an unpleasure and sleeplessness. In this research, we have measured three kinds of cicada singing noise at 16 points of urban area(Incheon, Gwangju, Busan, Gyeonggido Anyang). And then we analyzed the sound quality of the three kinds of cicada singing noise using by CADA-X signal process program. And we analyzed the acoustical characteristics by STFT(short time Fourier transform) which is a time-frequency analysis method. The characteristics of the cicada singing noise in terms of the sound quality and the time-frequency variation will be usefull to discover the relations between the human annoyance about the cicada singing noise and the acoustical characteristics.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.465-465
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• 2009

Wind power is one of the most reliable renewable energy sources and the installed wind turbine capacities are increasing radically every year. Although wind power has been favored by the public in general, the problem with the impact of wind turbine noise on people living in the vicinity of the turbines has been increased. Low noise wind turbine design is becoming more important as noise is spreading more adverse effect of wind turbine to public. This paper demonstrates the design of 10 kW class wind turbines, each of three blades, a rotor diameter 6.4m, a rated rotating speed 200 rpm and a rated wind speed 10 m/s. The optimized airfoil is dedicated for the 75% spanwise position because the dominant source of a wind turbine blade has been known as trailing edge noise from the outer 25% of the blade. Numerical computations are performed for incompressible flow and for Mach number at 0.145 and for Reynolds numbers at $1.02{\times}10^6$ with a lift performance, which is resistant to surface contamination and turbulence intensity. The objective in the low design process is to reduce noise emission, while sustaining high aerodynamic efficiency. Dominant broadband noise sources are predicted by semi-empirical formulas composed of the groundwork by Brooks et al. and Lowson associated with typical wind turbine operation conditions. During the airfoil redesign process, the aerodynamic performance is analyzed to minimize the wind turbine power loss. The results obtained from the design process show that the design method is capable of designing airfoils with reduced noise using a commercial 10 kW class wind turbine blade airfoil as a basis. The new optimized airfoil clearly indicates reduction of total SPL about 3 dB and higher aerodynamic performance.

• The Journal of the Acoustical Society of Korea
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• v.42 no.6
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• pp.584-593
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• 2023

This study attempted to develop repetitive impact sources similar to real-life floor impact noise and to find an assessment approach corresponding to this new impact source. The necessity for the development of the new impact source arises from the fact that issues related to floor impact noise in actual residential buildings mainly stem from children running. However, the standard impact sources which have been used for measuring and evaluating floor impact noise are of single-impulse type, which differs from the actual problematic impact sources. The study encompassed 18 evaluation items, and the results suggest that items applicable for assessing floor impact noise include psychological effects (annoying, becoming angry), disturbances to daily life (interference with sleep, disruption of relaxation), and physiological effects (elevated blood pressure). These items can be employed individually and, depending on the type of evaluation for floor impact noise, can be selectively utilized. By doing so, more comprehensive evaluations of auditory experiments in laboratories or assessments of residential noise in living environments related to floor impact noise could be conducted.

• The Korean Journal of Community Living Science
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• v.12 no.2
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• pp.33-45
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• 2001

This study was performed to investigate the degree of different stresses in university students of outer region of Seoul and to search the influence of food habit and nutrient intakes in stress. The data was collected by questionnaire method for self-diagnosed different stresses, dietary habit, and physical status and 24 hours recall for nutrient intakes. The subjects were 282 students attended at the lecture Food and Health. Diet balance was no difference with gender but food intakes were more diverse in female. Nutrient intake of male students was lower in vitamin A and riboflavin, but that of female was low in vitamin A and iron. The university students outer region of Seoul had more stress situation in frustration, deprivation and self-efface than in the stress of the noise and Type-A behavioral stress. Total self-diagnosed dietary habit score was better in the group of no susceptive overload stress than that of the high susceptive group. Same trend of dietary behavior score was in the group of no noise and anxiety-response stress than that in the susceptive groups. The quantity of nutrient intakes was correlated with different kind of stress. Niacin intake was positively related with the stress from life-events, and food induced stress. Thiamin intake was positively related with food induced stress. But the intake of iron, calcium, niacin and riboflavin were negatively related with the stress of noise. Therefore, we could concluded that different kind of stresses were influenced in dietary behavior and vitamin-mineral nutrient intakes. More research would be needed at the aspects of health promotion in the stressful situation of modern society.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.6
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• pp.1103-1111
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• 2000

With the rapid industrial development, a railway has become a main traffic means. But, rail traffic noise and vibration have become a major problem in urban area as well as a very serious issue in the living environment. Especially, noise and vibration induced by the rail operation have influenced on the residents' living nearby railway tracks. Nevertheless, adequate guidelines for the railway vibration are not yet established because of the lack of basic data and insufficient research works. In this point, the present study attempt to survey the effect and subjective response of railway vibration in urban area using questionnaire. This study also presents a basic data in establishing effective vibration plans for railway vibration in the future.

• Journal of Environmental Health Sciences
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• v.42 no.6
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• pp.438-449
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• 2016

Objectives: Exposure to airborne bacteria is associated with adverse health effects such as respiratory and infectious diseases. This study evaluated airborne bacterial concentrations in the living rooms, kitchens, and toilets of 30 homes. Methods: Bacteria were sampled with an MAS100 impactor in three spaces in the subject homes between April 2014 and February 2015. Bacteria were grown on TSA plates for 48 hours at $35^{\circ}C$. The bacterial strains were isolated and amplified by polymerase chain reaction. Results: The most culturable bacteria were found in toilets ($624.0CFU/m^3$, GM: $417.3CFU/m^3$), followed by in the kitchen ($503.8CFU/m^3$, GM: $324.9CFU/m^3$). The dominant genera identified were: Staphylococcus sp.(19%), Micrococcus sp.(16%), and Bacillus sp.(11%) in the indoor air and Bacillus sp. (30%) in the outdoor air. Gram-positive bacteria comprised more than half of all colonies. Conclusion: In this study, culturable bacteria concentrations were higher than those reported in other spaces. Therefore, it is important to control relative humidity and remove moisture to prevent bacteria from multiplying. Additionally, the dominant species in indoor air were Staphylococcus sp. and Micrococcus sp. These are found on the human skin, mucous membranes, and hair, so human activity can affect bacterial distribution. Therefore, cleaning and controlling moisture are important for reducing indoor bacterial concentrations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.763-768
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• 2012

Active window system which can reduce the environmental noises, such as traffic noise and construction noise, from an open window into a room was proposed in the previous works. The key idea of the proposed active window system was that the control sources are approximately collocated with the primary noise source in terms of the acoustic power for global noise reduction throughout the interior room. Moreover, because it is important not to intrude into the living space in the building environment, no error sensors were used and an open-loop control method using control sources at the window frame and the reference sensors outside the room was used for the proposed system. The open-loop control gain was calculated by the interior room model assumed as the semi-infinite space, and the interior sound field was estimated by Rayleigh integral equation under the baffled window model assumption. However, windows with a finite thickness should were considered for the calculation of the open-loop control gain of the active window system since these are representative of most window cases. Therefore, the finite thickness window model based on the Sgard's model was derived and the open-loop control gain using the interior sound field estimated by that model was calculated for active window system. To compare the performance of these two models, a scale-model experiment was performed in an anechoic chamber according to noise source directions. Experimental results showed that the performance for the thickness window model is better than the baffled window model as the angle with respect to the perpendicular direction is larger.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.3
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• pp.340-347
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• 2015

The Commission for Conservation of Antarctic Marine Living Resources (CCAMLR) is utilized to manage krill resources using acoustic data collection and a scientific observer program operating on the fishing boats. However, the acoustic data were contained seriously noise, example of background, spike, and intermittent noise, due to purpose of fish boats. In this study, the noise removal techniques were confirmed the potential of the acoustic data analysis. Acoustic system and frequency used in the survey were commercial echosounder (ES70, SIMRAD) and 200 kHz split beam transducer. Acoustic data were analyzed using Echoview software (Myriax), and general data analysis and new noise removal method was used. Although a variety of noise, most of the noises have been removed using the noise removal processing. We confirmed the possibility of analyzing the acoustic data obtained from fish boats. The results will be useful for analysis of the acoustic data acquired from krill fishing boats.