목적 : 소음으로 인한 스트레스가 다양한 시기능에 미치는 영향에 대해 알아보고자 하였다. 방법 : 안과적 질환, 수술이력 및 안구운동에 이상이 없는 젊은 성인 60명(23.12±1.26세)을 대상으로 하였으며 소음에 노출되기 전, 후로 지각된 스트레스 척도, 최대조절력, 조절반응량, 원-근거리 사위량, 비침습적 눈물 막 파괴시간의 변화를 관찰하였다. 결과 : 소음 스트레스에 노출이 된 후에는 지각된 스트레스 척도는 증가하였다. 푸쉬업 및 마이너스렌즈 부가 법으로 측정된 최대조절력과 조절반응량은 감소하였고, NITBUT 역시 감소하였으며, 원-근거리 사위량은 증가하는 경향을 나타내었다. 결론 : 본 연구의 결과를 통해 소음 스트레스는 시기능에 다양한 형태로 영향을 미치고 있다고 볼 수 있으며, 굴절검사 및 시기능 평가 시 주변 환경에 의한 소음 스트레스가 작용하지 않도록 검사실 환경을 구성하는 것이 중요할 것이라 사료된다.

The noise environment was evaluated using the ISO recommended NR evaluation curve and PSIL (Preferred Sound Interference Level) in order to investigate the onboard educational environment according to the noise in the Motor Vessel Saehaerim, a fishing training ship under making way. As a result, NRNs were measured at 37-61 dB in accommodation areas, 44-56 dB in work areas, 37-57 dB in educational and conference areas, 83-103 dB in engine areas and 65.3 dB and 51.2 dB in the work and education areas respectively based on PSIL. The NRNs, which evaluated the cabin of the experimental ship according to the purpose, exceeded all of the indoor standard noise recommended by the ISO, and the PSIL had a generally short conversational distance within 0.25-2.3 m and 0.75-1.3 m for teaching and work areas.

철도소음은 도시지역의 철도건설과 유지에 가장 큰 장애 요소 중 하나이므로 보다 효과적으로 철도소음을 저감하기 위한 연구가 활발히 진행되고 있다. 방음터널은 철도소음을 저감할 수 있는 가장 효과적인 방법 중 하나이나, 하절기 높은 내부 온도 증가로 인하여 궤도좌굴 또는 전력, 신호 등 선로 설비의 안정성을 저하시킬 우려가 있다. 이러한 온도 상승 문제는 통기 형 방음판을 이용하여 해결할 수 있으나, 방음터널 적용 시의 소음저감 성능에 대한 연구는 미흡한 상황이다. 이 논문에서는 수치해석을 통하여 통기형 슬릿방음판의 효과적인 방음터널 적용 방법에 대한 연구 결과를 제시하였다. 수치해석은 음향해석 프로그램인 Pachyderm Acoustics으로 모델링한 복선 방음터널을 이용하여 수행하였다. 철도소음은 기존 연구결과를 이용하여 모사하였으며, 슬릿방음판의 적용 위치가 다른 6가지 경우에 대하여 소음저감 효과 변화를 검토하였다. 음향해석 결과 20% 정도 의 슬릿방음판 적용 시에도 철도소음을 최소 5dB 감소할 수 있는 것으로 나타났다.

PURPOSES : The purpose of this study is to enhance the reliability of artificial intelligence for a noise-based pavement condition rating system (to a target performance of 95 %). METHODS : By comparing four types of pattern recognition artificial intelligence, this work acquires high-quality learning data and optimizes data learning through analysis of error characteristics. RESULTS : The system reliability improved up to 97 % (82 % in a prior study). In addition, 100 % was achieved for the E(F) condition grade, which has a direct impact on maintenance decision making. CONCLUSIONS : KNN-DTW (K-nearest neighbor dynamic time warping) is judged to be the most suitable type of artificial intelligence for a noise-based pavement condition rating system; a 4-grade system is the most suitable for classifying pavement condition.

There are many disadvantages to existing silencers used in power plants. Recently, high-performance silencers are required in society, so it is necessary to develop silencers accordingly. Therefore, in this study, to develop the flow silencer by taking advantage of the foamed aluminum, the property values such as loss coefficient and porosity were obtained through experiments, based on the Forchheimer's law. CFD analysis was performed by applying a porous modeling technique to foamed aluminum and the results were compared with experimental values. The error rate between the results of the experiment and the flow analysis is within about 2.79%, so the results of the experiment and the analysis agree relatively well. When the foamed aluminum was installed, the flow noise was reduced by about 5.14dB.

선체 부가물에서 발생하는 유동소음은 자체소음 관점에서 소나의 성능과 직결되고, 추진기 및 방향타와 상호작용을 통해 2차 소음원을 야기해 근접장 범위의 엄밀한 분석이 요구된다. 하지만 유동소음 해석에 적용되는 기존의 음향상사법은 음향 신호의 전파를 직접 모사하지 않는 간접법에 해당해 회절, 반사, 산란 특성을 고려할 수 없으며, 근접장 해석이 제한적이다. 본 연구에서는 격자 볼츠만 기법을 적용해 수중환경 유동소음의 전파과정을 직접 모사하였다. 격자 볼츠만 기법은 분자의 충돌과 흐름 과정을 통해 유동소음을 해석하는 기법으로, 압축성과 낮은 소산율, 낮은 분산율의 특성을 가지고 있어 소음해석에 적합하다. 선체 부가물 형상을 대상으로 RANS 해석을 통해 유동소음원을 도출하고, 유동-음향 경계면을 적용한 격자 볼츠만 기법으로 유동소음의 전파과정을 직접적으로 모사했다. 도출된 결과를 수음점의 위치에 따라 FW-H 결과 및 유체동압력 결과와 비교를 통해 근접장에서 타 기법 대비 격자 볼츠만 기법의 유용성을 확 인했다.

Aircraft noise loss in residential areas around small heliports is becoming more and more serious. Under the condition of long-term exposure to aircraft noise, it will not only cause physical and mental harm to human body, but also cause social and economic losses to the living environment around the airport. Therefore, it has been a serious contradiction factor in the community for a long time. This study points out the impact of noise caused by helicopter flying in aviation brigade of small heliport on the nearby residence area, The fixed noise monitoring system is set up to measure the aircraft noise every day. and selects the measurement site to facilitate the impact of noise caused by helicopter flight on the surrounding life.

The area around a certain airbase was affected by the noise of military helicopters, which seriously reduced the quality of the living environment in the surrounding area. In this paper, an automatic noise measurement system is set at 3 measurement points around the flight path of the 00 flight field. The fixed noise monitoring system is set up to measure the aircraft noise every day。 and selects the measurement site to facilitate the impact of noise caused by helicopter flight on the surrounding life. There is also a manual noise level measurement of the helicopter's maximum noise level for 7 days at 3 locations. Calculate the WECPNL value of 3 measuring points. Analyze the correlation between the aircraft noise evaluation unit WECPNL-Lden.

PURPOSES : The purpose of this study is to estimate the reduction in traffic noise in a double-layered specific porous pavement at roadsides based on variations in traffic volume and driving speed. METHODS : A statistical pass-by (SPB) method was employed in this study to measure noise. Variations in the following parameters were measured: running speed, heavy traffic percentage, and traffic volume. RESULTS : Quantitative analysis revealed that the double-layered porous pavement reduced noise levels by 9.16 dB(A) at a 95% confidence level at the sides of roads. CONCLUSIONS : As a countermeasure of traffic noise, porous pavement has been recommended. This research quantitatively proved that double-layered porous pavement can reduce traffic noise by more than 9.0 dB(A) at roadsides

The purpose of this study was to improve the noise measurement method of noise sources and the corresponding noise reduction measures during each manufacturing process closest to the workers in the large and hige power machine. To this end, the noise generated in the large and high power machine was measured and analyzed, and the frequency characteristics of noise sources and the causes of noise were identified. The noise map was used to predict the noise reduction effect. Moreover, it is expected that this will ultimately contribute to the reduction of human risks caused by the noise of the large and high power machine.

Industrial facilities need design to predict and reduce noise from design to prevent and reduce noise. The purpose of this study is to predict worker's environment and evaluate safety by analyzing noise inside underground blower room and air compressor room with fluid machinery in waste facility. This waste incineration facility was analyzed based on the ground floor, ground floor blower chamber, and air compressor chamber. The results of SPL(Sound Pressure Level) analysis at 1.5m away, which are frequently used to measure the SPL as a noise source, are as follows. SPL of basement level: 46.80[dB], SPL of ground layer: 48.57[dB]. As a result, it was expected that the noise level would be considerably lower than the 8 hours 50[dB] noise exposure per day.

PartI of this paper identified the location and size of the noise sources from the axial flow fans, and partII based on that, identified the magnitude of sound pressure from the case and the blade according to frequency in the range of 2200 Hz to 5000 Hz. The equation of Lighthill was used for calculation. Generally, when measuring noise, the analytical area was extended more than 1m from the outlet of the fan. To eliminate the effects of backflow coming from the rear of the fan, the analytical area was extended a little longer than 1m. From the results of the analysis, high noise occurs in the low frequency area, and the lower noise becomes in the high frequency area. The maximum sound pressure generated in the range of 2000Hz~5000Hz is 65dB at a distance of 1m and 82dB at the outlet of the fan. Noise of the fan mainly occurred around the blade and guide, and the noise decreased as the frequency increased between 2200Hz and 3400Hz, but the noise increased as the frequency increased between 3800Hz and 5000Hz.

In this study, numerical analysis was carried out to develop low-noise axial fans, which are often used for ventilation in houses. A commercial program and the turbulence models are used for the analysis of internal fan. Proudman acoustic power model and the Curle surface acoustic power model were used for analysis. As a result, the distribution of flow velocity and pressure around the blade and guide of the fan was high, and low in the center of the fan. Noise from the inner wall of the fan case and the blade surface was the highest at the body and vane connections of the blade, and low at the center of the vane and the center of the body.

PURPOSES : The purpose of this study is to estimate the reduction of traffic noise in a double-layered specific porous pavement based on the traffic speed variation. METHODS : The close-proximity method was used in noise measurement, and the running speed was measured at 10 km/h and from 50 to 80 km/h. RESULTS : From the quantitative analysis, it was found that the double-layered porous pavement reduced by 9.4 dB (A) on the average and 9.16 dB (A) at a 95% confidence level. CONCLUSIONS : The use of porous pavements have been recommended to minimize traffic noise. In this study, it is quantitatively demonstrated that the double-layered porous pavement can reduce the traffic noise by more than 9.0 dB(A).