• 한국소음진동공학회논문집
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• 제24권11호
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• pp.854-860
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• 2014

Workers engaged in car inspection works have been exposed to many occupational hazards including noise, particulate matter, and volatile organic substances. Noise-induced hearing loss(NIHL) is one of the leading health hazards among Korean workers. The aim of this study is to evaluate the noise levels in several car inspection shops by introducing the evaluation methods of KMOEL/OSHA and ACGIH. Six sites in central area of Korea were selected to monitor the noise levels of workers by personal and area sampling methods for two consecutive days in spring, summer, fall and winter seasons. Dosimeters have been used for this noise monitoring program. Obtained noise levels by the evaluation method according to KMOEL/OSHA are the range of 50.2~88.2 dB(A), these are lower than KOEL/OSHA standards level of 90 dB(A). But highest noise by ACGIH's evaluation methodology is recorded 92.3 dB(A) and is greater than NIHL standard level of 85 dB(A). So that many workers may be exposed to the dangerous noise environment. The higher the car inspection loads daily, the higher the noise levels in the sites. Seasonal fluctuation of noise levels at the process might give monitoring results with high variations. Area noise levels showed higher than those of personal sampling, which illustrate some high noise spots in the car inspection areas.

• 교육시설 논문지
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• 제28권3호
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• pp.3-14
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• 2021

Speech information of teachers is transmitted to students in classrooms so that appropriate aural environment should be provided for academic purposes. Many researches have been undertaken for classroom acoustics, and acoustic standards of domestic classrooms were suggested based on the reverberation time and background noise level. However, these standards are suitable for middle and high schools and so not consider the auditory ability by ages. As a precedent research, the present study was begun to suggest an acoustic standard for lower grade elementary school classrooms with children under age 9 who have not normal auditory ability. In order to do this, acoustic performances of the lower grade classrooms were measured and compared with the general classrooms. Also, change of acoustic parameters depending on the desk layout was measured and analyzed. The measured acoustic parameters were background noise, signal to noise ratio, RT, STI, D₅₀, and IACC. As a result, it was found that background noise is exceed the standard of 35dB(A) at the schools along the road sides. Also, it was shown that most of acoustic parameters are higher in the classrooms built recently rather than the old classrooms. Generally, there are not much difference of acoustic parameters among the various desk layouts but, better acoustic performances are acquired at the center line and the seats near sound source. Also, Higher IACC was measured at the seats on the center line facing the source squarely.

• 센서학회지
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• 제14권6호
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• pp.395-401
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• 2005

A highly stable quartz crystal microbalance (QCM) that showed a stability of frequencies and exhibited a very low noise level has been developed. The long-term drift was <0.05 Hz/h over a period of 10 h, and the short-term rms (root mean square) noise was <0.015 Hz. Our QCM sensor was used as a humidity sensor employing a poly(methyl methacrylate) (PMMA) polymer film as a hygroscopic layer, which showed good characteristics in the relative humidity (RH) range of $2{\sim}90%$ RH. Comparing the characteristics of the QCM sensor with those of other types of humidity sensors employing PMMA film as a hygroscopic layer, and with other QCM sensors employing other hygroscopic layers is represented.

• Progress in Superconductivity
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• 제9권1호
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• pp.56-61
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• 2007

The most recent improvement in the 10 V array system was carried out with focusing on noise reduction. We have evaluated the uncertainty of the 10 V Josephson array system after the improvement. The uncertainty evaluation of 10 V standard included a comparison with a programmable Josephson array system at 1 V. Every contribution to the measurement uncertainty was evaluated in the level of $10^{-10}$. The estimated combined uncertainty was found to be approximately $10^{-9}$ at 10 V, which was limited only by the indirect verifying method. In the near future, a direct comparison with another 10 V Josephson voltage standard is expected to be carried out to provide more accurate uncertainty evaluation for the KRISS Josephson voltage standard.

• 한국소음진동공학회논문집
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• 제19권10호
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• pp.1075-1082
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• 2009

Using GIS data of C-si as basic data when making noise map of road traffic, we estimated exactly the noise excess areas and consequently suggested the population and the area exposed to road traffic noise accurately. We made 3D noise map to assess regional distribution of noise quantitatively. The noise map consists of noise prediction model based on data base such as traffic volume and speed changes for estimating quantitatively the noise and 3D urban space model which includes locations of noise sources, 3D buildings, topography and roads. We made noise standard map according to land use conditions and compared this map to road traffic noise map, and consequently made excess noise map. Using excess noise map, we assessed areas which exceed environmental noise level standards and noise guidelines quantitatively and effectively through GIS spatial analysis, and consequently more accurate noise exposed area and noise exposed population could be estimated. To show buildings' outer walls noise exposure, we analyzed 3D urban noise distributions using 3D-analysis of GIS.

• 한국소음진동공학회논문집
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• 제26권1호
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• pp.20-26
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• 2016

This study investigated noise characteristics of air cleaners and humidifiers in terms of frequency domains and measurement directions. Noise levels of 31 air cleaners and 36 humidifiers were measured in an anechoic chamber according to the related group standards. As for air cleaners, 5 receiving points of 1 m off from front, rear, left, right and top surfaces of the product were considered. In case of humidifiers, 4 receiving points without the rear position were considered in the same manner as air cleaners. In each case, A-weighted equivalent continuous sound level was measured three times for 1 min. As a results, most of the measured air cleaners and humidifiers showed the highest noise levels at top directions due to the air ventilating location. In case of air cleaners, averaged noise levels of top and rear positions were 49.9 and 48.2 dB(A), respectively, whereas averaged noise level of other positions was all 45.2 dB(A). In case of humidifiers, averaged noise level of top position was 44.1 dB(A) whereas averaged noise levels of other positions were 38.7 to 39.1 dB(A). In addition, high frequency content of 1 kHz and 3.15 kHz to 4 kHz for air cleaners and middle frequency content of 500 Hz to 1.6 kHz for humidifiers showed significant contribution to determination of overall noise levels with correlation coefficient of 0.9 and above.

• Current Optics and Photonics
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• 제6권6호
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• pp.598-607
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• 2022

In this paper, a simple nondestructive technology is used to investigate unstained biological blood cells in three dimensions (3D). The technology employs a reflective phase-only spatial light modulator (SLM) for displaying the phase hologram of the object being tested, and a Fourier lens for its reconstruction. The phase hologram is generated via superposing a digital random phase on the 2D image of the object. The phase hologram is then displayed by the SLM with 256 grayscale levels, and reconstructed by a Fourier lens to present the object in 3D. Since noise is the main problem in this method, the windowed Fourier filtering (WFF) method is applied to suppress the noise of the reconstructed object. The quality of the reconstructed object is refined and the noise level suppressed by approximately 40%. The technique is applied to objects: the National Institute of Standards (NIS) logo, and a film of unstained peripheral blood. Experimental results show that the proposed technique can be used for rapid investigation of unstained biological blood cells in 3D for disease diagnosis. Moreover, it can be used for viewing unstained white blood cells, which is still challenging with an optical microscope, even at large magnification.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.476-479
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• 2007

Kitchen hood was used exhausting contaminants and heat during cook. But many people do not use it easily because of the noise. Therefore this study was measured the noise when kitchen hood was working according to air flow mode. Because there are no measuring and analyzing standards in the setting house, it was referred to KS C 9304(Korean Standard). The result was shown the higher sound level than 45dB. Also it was compared the air flow that measured in the house and specified the brochure during the operation of the hood.

• 한국소음진동공학회논문집
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• 제21권11호
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• pp.1005-1012
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• 2011

Diverse sports are appearing due to the enhanced quality of life and improved cultural standards of the present society. In particular, as golf gains greater popularity from the public, many golf ranges are being constructed near residential areas. However, the hitting noise generated by golf disrupt the pleasant living environment of neighboring residents to generate strong disputes related with noise. In this perspective, this study analyzed the characteristics and dispersion of sound pressure level according to the frequency of hitting noises generated in golf driving ranges and used this data to predict the range of effect through computer simulation. Thus, it is stipulated that these research results can be used as useful data for establishing effective plans in the future during civil complaints reported in relation to hitting noises in golf driving ranges.

• 조명전기설비학회논문지
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• 제23권8호
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• pp.124-129
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• 2009

최근 생활수준의 향상과 세계적인 녹색성장 정책으로 환경에 대한 관심이 고조되어, 전력분야에서도 환경친화적인 설비가 요구되어 지고 있다. 이에 따라 전력용 변압기도 소음저감에 대한 연구가 진행되어, 최근 55[dBA]급 154[kV] 저소음 변압기가 개발되었다. 저소음 변압기는 소음레벨은 저감되었지만, 중량 및 부피의 증가, 고무댐퍼의 적용 등이 변화가 있다. 이로 인하여 현장적용시 시험, 수송, 설치 및 운용 등에 대한 면밀한 검토가 필요한 실정이다. 따라서 본 논문에서는 효과적인 현장적용을 위해 소음레벨 기준치, 수송중량, 설치공간, 장기운용에 대한 사항을 검토하였다.