• Journal of the Korean Home Economics Association
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• v.43 no.4 s.206
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• pp.31-47
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• 2005

This study is a preliminary investigation into improving the environmental quality of schools. The purpose was to clarify the present conditions and reasons of noise in elementary schools located near airports and roads by noise level measurements and questionnaire surveys of subjective responses. fold measurements on equivalent and instantaneous noise levels, indoor and outdoor, were carried out in 3 schools during the periods 11th~ 13th of February and 2nd~ 7th of July,2003. The respondents were 94 teachers working in the 3 schools. The results were as follows. 1) Indoor noise levels of the 3 schools were 36.g~73 dB(A) in winter, and 46.9~ 91 dB(A) in summer. These values were higher than the indoor noise standard of 50 dB(A), except for the average of equivalent noise levels in winter.2) Outdoor noise levels of the schools were 41.1 ~ 101 dB(A) in winter, and 52.4~ 102 dB(A) in summer. These values were generally inappropriate relative to the standard for environmental noise of 65 dB(A). 3) The respondents showed relatively non- positive responses during school hours for interruptions by environmental noise.4) The frequently checked types of environmental noise of the schools were 'airplane noise','surrounding facilities', and 'traffic noise'. The frequently checked types of damage by environmental noise were 'Interrupting school hours' and 'Interrupting business'.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.594-601
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• 1997

Propeller fans are commonly equipped in outdoor units of air-conditioners to provide effective cooling in a dried heat exchanger. A new design technique was developed to satisfy requirements of aerodynamic and aeroacoustic performance, which employs the intersection method of two cylinders for mean camber line. Three proto-types of propeller fan including Palm-Shaped, Highly-Swept(PSHS) fan (proto 3)were not only to provide low lift forces for dipole sound, but also to reduce the organized tip vortices interacting with the fan guide causing narrow-banded rotating instabilities. Cross-correlation technique was applied to study flow noise source characteristics for three proto-type fans designed. The cross-correlations between a microphone at far field and a hot-wire sensor at near field show that flows near hub region of proto 3 fan are less organized and the flow structures especially at high flow rate coefficients for proto 3 fan are less correlated with noise generated than other proto-types fans.

• KIEAE Journal
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• v.9 no.1
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• pp.99-106
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• 2009

This study aims to survey the acoustical environment in the region around airport where there are various transportation noises such as aircraft noise, railway noise and traffic noise, and to analyze the subjective response on the noise to the people who live in house or work in office nearby airport. Measurement and subjective response evaluation were carried out at the same time and outdoor noise level was measured all day long to calculate one day results such as average Leq or one day WECPNL etc. The results showed that the military aircraft produces very high level comparing with commercial aircraft, for instance the sound level of commercial outdoor was lower than that of military aircraft indoor. Double and triple window were more effective for controlling the noise than single window, which showed the possibility of sound insulation treatment by installing windows having higher sound insulation performance. Finally the subjective response was resulted that the most annoying noise is from aircraft and counterplan they hope is 'airport moving out'. Leq 65 dB(A), the criteria value of sound insulation treatment, was corresponding to the subjective response of median annoyance '4' out of 7th scale.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.472-472
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• 2009

The safety of cultural properties, medical treatment and electrical communication equipments in a building was hardly considered against the earthquake induced vibration, while the integrity of the building structure has been taken into account through the resistant earthquake design. This paper presents design of a seismic isolation table for both indoor and outdoor electrical communication equipment. First of all, artificial earthquake waves compatible with floor and ground response spectra for electrical communication equipments are generated using previously recorded seismic waves. Two kinds of one-degree-of-freedom seismic isolation table systems: spring-linear damper and spring-friction damper systems are considered and their responses to artificial earthquake waves are simulated. Design parameter study for two seismic isolation tables are performed through simulations and a seismic isolation table for both indoor and outdoor electrical communication equipment is designed considering the simulation results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.333-337
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• 2003

The use of reactive shearing structural intensity to place small patches of constrained layer damping material in order to achieve the largest reduction in the radiated sound power of Air-conditioner outdoor unit is described. The normal surface velocity of each panel was measured using a laser doppler vibrometer. Experimental results indicated that patches of constrained layer damping material placed over areas of high reactive structural intensity reduced the radiated sound power significantly more than patches of the same area placed over areas of low reactive structural intensity

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.4
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• pp.175-184
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• 2017

With the improvement of living standards, the ventilation for the mitigation of indoor or outdoor air-pollution problems has recently attracted a lot of attention. Consequently, the ventilation for the supply of outdoor fresh air into a room is treated as an important building-design factor. The ventilation is generally divided into the forced and natural types; here, the former can control the ventilation rate by using mechanical devices, but it has the disadvantages of the equipment costs, maintenance costs, and noise generation, while the latter is applied to most workshops due to the absence of noise and the low installation and maintenance costs. In this experimental study, the ventilation performance of a typical rotating-type natural ventilator, which is called a "wind turbine," was investigated with the outdoor-wind velocity and the indoor/outdoor-temperature difference. From the experiment results, it was confirmed that the temperature difference of $10^{\circ}C$ corresponds to the ventilation driving force with an outdoor-wind velocity of 1.0 m/s. Additionally, the intake-opening area of a building also exerts a great effect on the ventilation rates.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.727-734
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• 2008

This research presents a laboratory study about difference of subjective response between with and without pictures. A main source is impulsive sound caused by leisure shooting. The sources are sampled from outdoor noise and their levels range from 40 to 75 dB at the interval of 5dB. The noise unit is based on A-weighted sound exposure level (ASEL; $L_{AE}$). To make equal ASEL of outdoor noise, finite impulse response (FIR) filter is applied to the originally sampled source to include the effect of distance attenuation. The evaluation method of the jury test adopted a Semantic Difference(SD) Method. The intersection point which two lines crossed was used as reference point. The intersecting point of mean response rating between with and without pictures was approximately 44ASEL and that of %HA was about 60ASEL. In the result of the test, the negative effect of pictures was given at a lower levels than intersection point while the positive effect was given at a higher levels than that.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.5
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• pp.355-364
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• 2002

The goal of this research is to reduce noise level of an outdoor unit of air conditioner by changing its dynamic characteristics using SDM (structural dynamics modification) technique. At first, the emitting noise was measured and analyzed. The measurement records show the most critical frequency components which influences on the noise level. Then it was tried to move the natural frequencies outside the critical frequency region by SDM. Since it is very difficult to get a reliable FE model of air conditioner, experimentally measured frequency response functions were used to derive sensitivities that are very important to obtain design changes. The positions of modification and the thickness of modifying structures were determined to improve the dynamic characteristics of air conditioner. The recommended design guideline to move its natural frequencies outside the targeting frequency range was obtained. Then in order to prove its effectiveness, the changed design was experimentally tested and found that the SDM result is very effective to reduce not only its vibration but also its emitting noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.530-531
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• 2009

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.137-138
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• 2014