• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.376-380
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• 2009

The transmission noise characteristics through the ventilating duct was conducted numerically using SYSNOISE. A ventilating system is usually composed of mufflers for preventing noise transmission from the ventilator into indoors through the ducts and distributors for transferring air to or from each room. The transmitted noise characteristics of distributors which have different branch angles and of mufflers having different shapes were analyzed numerically. New duct element combining a muffler and a T-shaped distributor was developed for better noise reduction in this paper. New element's performance was shown numerically.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1444-1449
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• 2000

This environmental influence of the noise produced by a number of air-conditioner out-door units in a multi-unit housing is predicted and evaluated. The method based on Ray tracing theory and mirror image source theory is utilized. Each ventilation window in a machine room is considered as a sound source which contributes to the overall noise level of the surrounding environment. The adopted method has been found a very efficient tool to assess the environmental noise impact.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.488-492
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• 1997

원자력 발전소의 공조 시스템에 설치되는 덕트형 소음기를 설계.제작하여 감음성능 시험, 내진해석, 내진시험, 난연시험 및 기밀시험 등을 수행하여 각각의 요구조건에 적합한 소음기를 설계.제작한 결과 원자력 발전소에 기 설치된 소음기와 동등한 성능을 갖는 것으로 나타났다. 소음기를 설계, 제작, 시험하는 과정에서의 노-하우를 바탕으로 어떠한 요구조건에도 만족하는 제품을 국내에서 설계.생산할 수 있는 기술 확보에 있다.

• Journal of KSNVE
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• v.9 no.2
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• pp.265-272
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• 1999

A LMS algorithms has been widely used for an adaptive filter algorithm in active noise control systems. But this algorithm has poor convergence and it is very difficult to select optimal convergence parameters in this algorithm. In this paper, a fuzzy LMS algorithm where the convergence parameters are computed using a fuzzy logic controller was proposed. A proposed algorithm was applied to active noise control system in HVAC(central Heating Ventilation and Air Conditioning) ducts. The experimental ducts and experimental apparatus were designed and manufactured for experiments, and the modelling of the experimental ducts was also performed for computer simulations. Computer simulations and experiments were performed to show the effectiveness of a proposed algorithm.

• Journal of the Korea Society of Computer and Information
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• v.21 no.3
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• pp.91-96
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• 2016

We have surrounded undesired living noises in our life. One of biggest noises coming out of range hood during cooking in the kitchen. A range hood is one of the most important appliances in the kitchen because it ventilates polluted air out during cooking, and maintains air quality in the kitchen. But current kitchen range hoods bring up some issues; First, the range hoods consume massive amount of standby power not in use condition. Second, current models have designed manual fan operating system with sudden onset of noise with starting. In this paper, we propose an auto control system entire processes from air ventilation to noise reduction. Our system is consist of three parts (Eco-sensors pack, Main Controller and Active Noise Controller); Eco-sensors pack detects air pollution of kitchen areas and sends the detection values to Main Controller. Main Controller determines operation of range hood by detected values. Active Noise Controller is located inside of the range hood. It received starting signals from Main Controller which elicits degrees of polluted air condition and fan operating speed from 1 to 3. Once Active Noise Controller detected the signals, it runs a ventilating fan until new value from Main Controller becomes 0. while the range hood works, A noise cancellation algorithm inside of Active Noise Controller become activated to reduce levels of noise. As a result, the proposed system clearly shows reduction in power consumption include standby power and decreases in levels of noise.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.4
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• pp.475-482
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• 2016

The active control of noise generated by the compressor and transmitted out of the machine room through the windows is implemented based on the FIR filter. The machine room contains most of noise sources of electric home appliances, air-conditioners and refrigerators, for example. To actively reduce the noise from the machinery room. In this paper, the transfer function of the controller for minimization of the acoustic power transmitted through the windows is mathematically formulated. The transfer functions required for implementation of the active controller are the measured. The measurements are conducted in this initial stage under the operation of the compressor with no load. For improvement of the reliability of the transfer function of the compressor to the acoustic power, additional operational measurements are performed. The real time controller is implemented based on the FIR filter using the measured transfer functions and the performance of the active controller is estimated. Control performance is measured about 3 dB ~ 10 dB in reduction of the sound power at the peaks of the compressor noise.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.6
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• pp.14-22
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• 2008

This study is aimed at suggesting a linear-type diffuser which is excellent in terms of range and elegance like existing diffusers in which amount and direction of wind can be freely controled, out of linear-type diffusers with the highest possibility to be adopted for living space of apartments whose height between floors is not so high and utilizing the linear-type diffuser in design. For the purpose, I examined necessary flow and noise properties of linear-type diffusers. Besides, I evaluated its ventilation capacity for persons in there by applying this in the actual living space. I evaluated features and air blast and found that in time of horizontal and vertical effusion, its T/L ratio is 1-1.5, similar to existing cardioid-type linear diffusers, while in time of slope effusion, it is similar to horizontal effusion in terms of range and it has medium figure in terms of pressure drop and effusion speed, indicating it can provide safe and pleasant indoor environment for persons in there in terms of ventilation.

• Korean Journal of Health Education and Promotion
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• v.18 no.2
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• pp.141-156
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• 2001

This study was performed to identify the occupational diseases in the dental technicians working in Korea, and to elucidate the main related affecting factors for the occurrence of the occupational diseases. The research was carried out using a mail questionnaire and data collection was done for two months from April 15, 2000. The questionnaires were delivered to 1000 dental technicians working at 250 dental laboratories which were chosen among the total 1330 dental laboratories in south Korea. And 763 questionnaires were collected, then 739 questionnaires were used for a logistic and a multiple regression analyses. The results obtained in this study are summarized as follows: 1. The occupational diseases in the dental technicians included pneumoconiosis, chronic bronchitis, asthma, pneumonia, hyposmia, allergic dermatitis, eczema, contagious dermatitis, central nervous disorder, dysfunction of finger, vertebral disorder, dysfunction of interphalangeal joint, ophthalmitis, auditory dysfunction, otitismedia, optic trauma, and bum. 2. The main related affecting factors for the occurrence of the occupational diseases in the dental technicians were elucidated as follows: On the ccurrence of chronic bronchitis, vibration of equipment and job career were affected positively. On the ccurrence of asthma, job career and career on current working part were affected positively, but exhaust ventilation, work hour were affected negatively. On the occurrence of eczema, career on current working part and vibration of equipment were affected positively, but personal protective equipment, local exhaust ventilation, isolation of gas source were affected negatively. And eczema was occurred more in methyl methacrylate work than in any other work part. On the occurrence of finger dysfunction, vibration of equipment and noise of work place were affected positively. But personal protective equipment, local exhaust ventilation, isolation of dust and gas source were affected negatively. But finger dysfunction was occurred more in metal polishing than in any other work part. On the occurrence of auditory dysfunction, noise of work place were affected negatively. The results obtained in this study can give a valuable information for a prevention of the occupational diseases in the dental technicians working in Korea, and for keeping them in healthy. This study also can be helpful for a researcher who is aiming at a identification of occupational diseases and a elucidation of related affecting factors in a similar occupation.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.4
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• pp.364-374
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• 2006

Natural ventilation technique could be the substitute for or the complement to the local exhaust ventilation system in the sense of protecting work environment. Moreover, it has many strong points ; almost no mechanical parts, no energy use and no noise. If applied appropriately, it could have the very high ventilation rate and save a lot of energy expense. But, it depends on the outdoor environment, especially temperature and wind speed/direction. Predicting the capacity of natural ventilation is not an easy job because it comes from both buoyancy and wind effect. Another problem is too much flow through the ventilator especially in winter time due to too much difference between indoor and outdoor temperature. Thus some ventilators in industries are sealed by door or plastic sheet, resulting in bad work environment. Various types of dampers are used to control the flow rate through ventilators. The capabilities of flow control by damper has not been estimated. In addition, it was not tested whether the damper could obstruct the flow through ventilator when fully opened. To answer these questions, 4 types of dampers were tested by using computational fluid dynamics. 10 different configurations includes no damper, full open and half open. Flow rates were estimated and airflow fields were analysed to clarify the before-mentioned questions. The dual type damper was the best choice for controling the capability of ventilator. In addition, the upward grill type damper was the best for not obstructing the air flow when fully opened.

• Journal of the Korean Institute of Educational Facilities
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• v.18 no.4
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• pp.3-12
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• 2011

This study investigates interior and exterior environments and arrangement forms of school buildings from elementary to high school which were recently built in Daegu since the 7th Educational Curriculum. In addition, this study analyses how outside noise affects inside environment of schools. This study found that the noise level criteria of school facilities(such as exterior learning sites and outer walls of school buildings) adjacent to street of one side satisfiedly corresponded to the level and criteria, 65dB(A), of school health law. However, the noise level and vibration criteria of school facilities adjacent to street of two sides did not satisfiedly corresponded to the level or criteria, 65dB(A). In case of classrooms, the inner noise of educational facilities with windows closed and also close to both the street of one side and of two sides satisfiedly corresponded to the level or criteria. 55dB(A), of school health law. In spring and tall, the windows are more open them usual for ventilation, and leaving windows open can lead to noise from outside. Thus, it is urgent to prepare for this situation.