• 소음진동
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• 제10권5호
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• pp.873-879
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• 2000

Experimental investigation was conducted to study the effects of pitch angle maximum camber on the performance and noise of an axial-flow fan used in outdoor-unit of air -conditioner. For this study the axial-flow fan whose pitch angle can be varied was made and the Specific sound Pressure Level and other coefficients were measured using the anechoic fan tester. It is found that pitch angle affects more severly than the maximum camber on the fan performance. On the while the maximum camber affects much on the specific sound power level. Present results show that it is important to choose the optimum pitch angle and maximum camber to design the high-performance and low-noise axial-flow fan and specific noise measured in the anechoic fan tester can be sued effectively for the design of low-noise fan.

• 한국주거학회논문집
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• 제19권1호
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• pp.1-8
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• 2008

This study is an attempt to understand the floor-specific characteristics of facade road traffic noise in apartment buildings. For this purpose, it sampled a total of seven roadside apartment building complexes: three with no soundproof bar barrier installed at roadside, one with a forest buffer zone, one with a sound-absorbing hill, and two with soundproof barriers. The measured noise level was highest on the 5th floor of apartment buildings with no soundproof barrier, and the upper stories from the 5th floor showed lower-noise measurements in order. For apartment buildings with soundproof barriers, however, the noise level was lower on the 10th floor than the 5th floor. Two apartment building groups--one with a sound-absorbing hill and the other with no soundproof barrier--showed similar measurement results in the floor-specific characteristics of facade road traffic noise. This suggests that such installations have little sound insulation effect. In the apartment building complex with a forest buffer zone around it, a slight sound insulation effect was measured on the lower floors of the buildings.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.548-553
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• 1998

The specific noise level of 18 rotary compressor mufflers were measured and these data were analyzed by the Taguchi robust design method and the neural network. The optimal design value obtained by the neural network generally showed good agreement with that by the Taguchi method. The effects of eight important design variables on the specific noise level were discussed.

• 한국음향학회지
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• 제19권6호
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• pp.23-27
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• 2000

소음이란 듣고 싶지 않거나 시끄러운 소리로 정의될 수 있다. 이동전화 벨소리가 특정한 상황에서 너무 크다면 소음으로 간주된다. 이동전화 벨소리의 특정한 수준을 소음으로 분류하기 위해서는 특정한 상황에서의 벨소리 수준에 대한 평균호감도를 평가하는 것이 유용하다. 본 논문에서는 이동전화 벨소리의 여러 수준(dBA)에 대한 평균호감도를 벨소리의 종류(벨/멜로디), 성별(남/녀), 장소(거리/사무실)에 대하여 평가한다.

• 한국환경보건학회지
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• 제45권6호
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• pp.569-576
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• 2019

Objectives: The main purpose of this study was to assess firefighters' daily personal noise exposure and explore noise levels related to specific tasks and their contributions to total noise exposure using 24-hour full-shift noise exposure measurements with task-based data. Methods: Noise exposure was assessed for eight firefighters (two rescuers, two drivers, and four suppressors) using time-activity diaries. We collected a total of 24 full-shift personal noise sample sets (three samples per a firefighter). The 24-hour shift-adjusted daily personal noise exposure level (L_ep,d), eight weekly personal noise exposures (L_eq,w), and 40 task-specific L_eq values (L_{eq activity}) were calculated via the ISO/NIOSH method. Results: The firefighter noise-sample datasets showed that most firefighters are exposed to noise levels above EU recommended levels at a low-action value. The highest noise exposure was for rescuers, followed by drivers and suppressors. Noise measurements with time-at-task information revealed that 82.3% of noise exposure occurred when checking equipment and responding to fire or emergency calls. Conclusions: The results indicate that firefighters are at risk of noise-induced hearing loss. Therefore, efforts at noise-control are necessary for their protection. This task-specific noise exposure assessment also shows that protective measures should be focused on certain tasks, such as checking and testing equipment.

• 한국유체기계학회 논문집
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• 제1권1호
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• pp.32-40
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• 1998

Aerodynamic performance of a cooling fan of driving motor was enhanced modifying the vane-shroud configuration. Performance of a target model was evaluated to obtain baseline data. The aerodynamic performance and sound pressure level were tested and measured with different numbers of vane of increased length. The tested models show high and stable performance and low values of specific noise level. The long vane-shroud structure induces more stable through flow and decreases the tip leakage flow, which contributes to the increases of performance and efficiency. The sound pressure level increases for the modified model, however, specific noise level decreases.

• 한국안전학회지
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• 제11권4호
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• pp.135-142
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• 1996

Prolonged in-plant personnel exposure to high noise levels results in permant hearing damage. There are no way to correct this hearing damage by treatment or use of hearing aids. Therefore, every employer is responsible for providing a workplace free of such hazards as excessive noise. This study was carried out to evalute and predict a given noise environment based on specific limit as the noise guarantee for a newly-founded petrochemical plant. The maximum total sound level should not exceed 85dBA in the work area, except where the area is defined as a restricted area and 70dBA at the plant boundary. Prediction of the noise levels within the plant area for a newly-founded petrochemical plant was achieved by dividing all plant area into 20m$\times$20m regular grid spaces and noise level inside the area or unit that in-plant personel exposure to high noise levels was estimated computed into 5m$\times$5m regular grid spaces. The noise level at the grid point that was propagated from each of the noise sources(equipments) computed using the methematical formula was defined as follows : $SPL_2$=$SPL_1-20log{\frac{r_2}{r_1}}$(dB) where $SPL_1$ =sound pressure level at distance $r_1$ from the source $SPL_2$=sound pressure level at distance $r_2$ from the source As a result, the equipments exceeded noise limit or irritaring noise levels were identified on the specific grid coordinates. As for equipments in the area that show high noise levels, appropriate counter-measures for noise control (by barriers, enclosure, silencers, or the change of equipments, for example) should be reviewed. Methods for identifying sources of noise applied in this study should be the model for prediction of the noise levels for any newly-founded plant.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.371-376
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• 2003

The objective of this paper is to compare the site-to-site variability of ISO 10844 pass-by-noise test sites. In order to investigate the site-to-site variance of test surfaces, European commercial tires are tested at seven different test sites. Three Korea test sites and four Europe test sites are selected.. The pass by noise test is executed according to a 2001/43/EC regulation. A]though the ISO surface has a very specific track composition, it does not reduce the variation of pass-by-noise measurements over the surface of test sites. This paper shows that the test results of pass-by-noise level are different depending on the test sites. The correlation obtained in this work is able to predict the pass by noise level for certain test site using the data measured from another test site. 17he prediction value is range with an error within 1dB(A).

• 한국소음진동공학회논문집
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• 제25권4호
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• pp.255-265
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• 2015

Shelter system is applying to weapon systems as usage of performing specific mission with arranging several electronic equipments and operators. Recently the electronic equipments is changing from development products to COTS(commecial off-the-shelf) for demonstrating high performance at low cost. As internal operators of shelter system conduct several missions for specific or long time in this present situation, one of the most important element considering the best combat power is internal noise level. Therefore, I desire to analyze the features and foresee multiple noise level with test for conforming whether requirements of design is met or not in this research paper.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.60-65
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• 2014

Shelter system is applying to weapon systems as usage of performing specific mission with arranging several electronic equipments and operators. Recently the electronic equipments is changing from development products to COTS(Commecial on-the-shelf) for demonstrating high performance at low cost. As internal operators of shelter system conduct several missions for specific or long time in this the present situation, One of the most important element considering the best combat power is internal noise level. Therefore, I desire to analyze the features and foresee muliple noise level with test for conforming whether requirements of design is met or not in this research paper.