• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.50-54
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• 1996

최근들어 전력수요와 상시 전력공급이 요구되는 시설이 증가함에 따라 독립적으로 전력을 공급할 수 있는 상용 또는 비상용발전기가 많이 이용되고 있는 추세이다. 이러한 소형 발전시스템에는 디젤엔진이나 터빈 엔진에 발전기를 연결하여 전력을 공급하는 코젠 시스템(co-generation system)이 주로 이용된다[1]. 일반적으로 코젠시스템은 운전중에 매우 높은 수준의 소음이 발생되므로 건물 주변이나 사람의 왕래가 잦은 곳에 설치되는 경우에 필히 소음저감을 위한 대책이 필요하게 된다[2,3]. 본 사례는 대형놀이시설의 전력공급용으로 설치된 옥내(발전실내)의 상용/비상용 발전기(3600 KW 디젤엔진 2대)에서 발생한 상당량의 소음이 놀이시설주변까지 전달되어, 소음원 및 그 전달경로를 규명하고 대책을 수립한 내용이다. 놀이시설의 개장을 앞두고 소음문제가 발생되었기 때문에 신속하고 현실적인 해결책의 적용이 요구되었으므로 발전기 및 발전실 주변의 소음레벨 및 주파수특성의 분석을 통하여 주소음원을 규명하는 방법을 택했다. 분석결과로부터 주 소음원은 엔진 배기구에서 발생되는 저주파수 특성을 갖는 소음으로 규명되었고, 그 주파수특성에 적합한 흡음 및 반사특성을 동시에 갖는 조합형 2차 소음기를 추가로 설치하여 발전실 주변소음레벨을 크게 저감할 수 있었다.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.11
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• pp.1193-1197
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• 2005

The low frequency noise below 200 Hz, including inaudible infra-sound, is known to affect human physiology ; circulation, respiration, nerve, endocrine, etc. Legislation has been introduced in several countries regarding evaluation guideline and measurement method of low frequency noise. In this work, low frequency characteristics of the Seoul subway transportation system was investigated in terms of the noise level and spectrum in the interior of running passenger car and the subway station. The interior sound pressure level of the passenger car was between 60 and 105 dB in the frequency range of $1{\sim}200\;Hz$ and varied with car speed. The marked sound pressure level peak at 8 Hz, infra-sound, observed for the most of Lines is shown to correspond to the resonance frequency of passenger car. The level of station platform noise was lower than the interior noise of running car because of the lower speed at arriving/departure. The results indicated that the interior noise level of running passenger car was inside the oppressive feeling region, proposed by Ochiai, in the frequency range of $20{\sim}80\;Hz$ which makes a little concern.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.8
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• pp.787-794
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• 2010

Recently, with sudden increase of supplying rate of cars and quantity of goods transported, traffic noisy becomes one of important factors obstruct environment of exhibition and view facilities have purpose in calmness and unsatisfaction about this is high now. Therefore, in case of exhibition and view facilities, it has to be grasped that satisfaction degree about the noisy in and out of the exhibition room by performing effect valuation on traffic noisy from design step. However the level of internal noise cannot be measured at the design phrase of the structure due to the noise of traffic. Up until now a walls transmission loss, based on the law of mass, is predicted using this method. However measuring the internal sound level after actual construction reveals that there is a large difference from measurements made at the design stage, and it is very difficult to find a solution after the opening of the structure. From research looking from this perspective the internal sound level was predicted- calculating the internal sound absorption ability, using acoustic simulation and loss prevention of an insulated wall- based on data collected to evaluate the internal sound of an exhibition room at a Folk Museum adjacent to a freeway. The results of this research are considered to provide important data for the prediction of internal sound level at the time of construction of exhibition facilities similar to this.

• The Journal of the Acoustical Society of Korea
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• v.39 no.4
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• pp.322-330
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• 2020

This study investigates the far-field noise from three Falcon 9 vehicle launches from Vandenberg Air Force Base, CA, USA, as measured from the same location within the nearby community of Lompoc. The overall sound pressure levels for the three launches are shown to be similar, but some differences in the early launch period are thought to be weather-related. The peak directivity angle in overall level is approximately 65 deg, which is consistent with horizontally-fired, static rocket data. For the third launch, waveforms and spectra are analyzed for different events during the launch sequence. The measured spectral bandwidth decreases with time, but spectral levels remain above the ambient noise throughout the main-engine firing. Additionally, late-launch phenomena observed in the data appear to be correlated with main-engine cutoff and second-stage engine start.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1991.04a
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• pp.53-56
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• 1991

산업구조의 급속한 발전과 공업화는 사회구조의 변화 및 대도시로의 인구집 중, 고밀도화, 교통량의 증가를 초래하여 이로부터 기인한 도시지역의 환경 오염 문제는 쾌적한 인간생활을 위협하는 단계에까지 이르렀다. 그중에서 소 음에 관한 문제도 대기 및 수질의 오염과 동시에 도시생활 환경에 많은 영 향을 미치게 되었다. 도시 소음의 주 원인은 주로 도로교통소음이며 이는 기 하급수적으로 늘어가는 자동차의 양에 의해 더욱 심해지고 있다. 따라서 현 재 우리나라에서도 주거지역 및 준주거지역 등의 지역별 소음도 규제 및 신 설되는 공동주택 단지에서의 소음레벨규제등이 있긴 하나 이들은 상당히 소 극적이며 미온적일 뿐 아니라 실제 거주하는 주민들의 반응과는 상당한 차 이를 보이고 있으며 더욱이 주민의 소음에 대한 주관적 반응을 적절히 표현 할 수 있는 지표마저 명확하지 않은 실정이다. 이러한 관점에서 본 고찰에서 는 피험자들의 주관적 반응을 실험할 때 발생하는 변수요인들을 통제 할 수 있는 실험 실시행 청감실험을 실시하기에 앞서 대상지역의 도로교통소음을 여러가지 평가척도에 의해 평가한 후 그 현장에서 이 소음에 노출된 피험자 들의 반응을 파악하여 청취자들이 인지하는 소음레벨을 적절히 평가하는 지 표를 찾고자 한다.

• Explosives and Blasting
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• v.29 no.2
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• pp.81-88
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• 2011

Most of the blast pollution that causes complaints is noise and vibration. Hence, special attentions need to be paid to controlling the underwater noise in designing blasting for those areas. This study estimated underwater sound pressure using distance from blasting and charge per delay and underwater sound pressure level using the underwater sound pressure. To identify the validity of the estimated value, the study demonstrated the results at other areas and compared actual results with estimated results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.447-451
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• 1997

주변에 소음 유발 기기가 많아 소음 레벨이 열악한 태안화력 1,2호기 사이의 사무실을 제어 대상으로 하여 여러 형태의 유리창에 대한 투과 손실을 이론적으로 예측하였으며, 기존 형태를 대체하여 현장에 적용시의 삽입 손실을 추정하였다.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.4
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• pp.232-238
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• 2012

In this study, the noise mapping simulation is executed to design an effective barrier reducing noise levels of a school site. The geographical features of the ambient site and the school buildings are modelled in detail in order to consider sound propagation, deflection, and absorption phenomena etc. The main sound source, sound power level of expressway, is estimated on the basis of measured noise levels at several points of the site. The noise mapping simulation is performed by using ENPro, environmental noise prediction program based on ISO 9613 to analysis the effectiveness of noise barrier. Consequently, the noise barrier is designed to meet an environmental noise standard and satisfy low cost and safety conditions.

• The Journal of the Acoustical Society of Korea
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• v.37 no.5
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• pp.369-377
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• 2018

This study investigated the effect of noise and reverberation on subjective measure of speech transmission performance for elderly person with hearing loss in residential space through listening test. Floor impact, road traffic, airborne, and drainage noise were employed as the residential noise, and several impulse responses were obtained through room acoustical computer simulation for an apartment building. Sound sources for the listening test consisted of residential noises and speech sounds for boh the young (the original sound) and the aged (the sound filtered out by filters with frequency responses of hearing loss of 65 years elderly person). In the listening test, subjects evaluated speech intelligibility and listening difficulty for the presented word ($L_{Aeq}$ 55 dB) at three noise levels ($L_{Aeq}$ 30, 40, 50 dB) and three reverberation times (0.5, 1.0, 1.5 s). Results showed that the residential space with noise level lower than equal to 50 dB ($L_{i,Fmax,AW}$) for jumping noise and 40 dB ($L_{Aeq}$) for road traffic, airborne, and drainage noise had speech intelligibility of 90 % and over and listening difficulty of 30 % and below. Speech intelligibility and listening difficulty for the aged sound source was shown to be 0 % ~ 5 % lower and 2 % ~ 20 % higher than those for the young sound source, respectively.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.8
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• pp.1170-1179
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• 2009

The purpose of this work is to predict the low frequency aero-acoustic noise generated from the horizontal axis wind turbine, NREL Phase VI for the whole operating conditions of various wind speeds using large eddy simulation and Ffowcs-Williams and Hawkings model provided in the commercial code, FLUENT. Because there is no experimental data about wind turbine noise, we first of all compared aerodynamic performance such as shaft torque and power with experimentally measured value. Performance results show a good agreement with experimental data within about 0.8%. As the wind speed increases, the overall sound pressure level and the sound pressure level by the quadrupole and dipole source show a increasing tendency. Also, sound pressure level is proportional to $r^{-2}$ in the near field and $r^{-1}$ in the far field according to the increase of distance from the center of hub of wind turbine. According to 2 times increase of distance, sound pressure level is reduced by about 6dB.