• The Journal of the Acoustical Society of Korea
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• v.42 no.4
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• pp.285-297
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• 2023

The present study aims to investigate the acoustic performance of the creative convergence classrooms in Korea used by elementary school students under the age of 9 introduced through the school space innovation project. In order to do this, acoustic performances of three creative convergence classrooms were measured. The measured acoustic parameters were background noise levels, Reverberation Time (RT), D₅₀, Speech Transmission Index (STI), and Inter-Aural Cross Correlation (IACC). Also, acoustic parameters including Transmission Loss (TL) and standardized level difference (D_nT) have been measured for the analysis of sound insulation performance of walls. In addition, the noise level was measured according to the opening conditions of doors and windows in the classroom. As a result, background noise level was measured at an average of 28.0 dB(A) to 32.8 dB(A) when the air conditioner was not operated, and the RT did not exceed 0.6 s. There were differences in IACC according to various desk layouts, and IACC values were high in the center line and the seats near the sound source. In particular, higher IACC was measured at the seats on the center line facing the source squarely. Regarding noise level in the classroom according to the opening conditions of doors and windows, the standards were exceeded when all windows, or windows and doors front onto the corridor were opened.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.102-107
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• 2009

Window system is an essential component for lighting, ventilation and thermal environment in buildings. Moreover, as balcony extension in apartment houses become legalized, the performance requirements of window systems in balcony space are getting complicated. However, at this moment, five properties of the windows are used to represent the performance aspects of the system, including wind resistance, air tightness, water tightness, sound insulation, thermal resistance. And such single properties are not capable to express the performance of a space with the window systems in terms of performance concept. A performance analysis with wholistic approach is required to see the effect of the window system in built environment. Thus, performance-based approach should be established, which will be able to evaluate the goal/function and comfort of occupants/owners. As the first step to develop the performance indicator for the window systme for balcony space, this study conducts a survey to find the required performance aspects. A complete set of performance-based indicators will be developed with verification methods in the later stage of research.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.356-362
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• 2016

Light-weight concrete uses forming agents for reducing weight and high heat insulation property. However, the forming agents make problems of decreased volume and compressive strength of the concrete. This research aims to having weight-reduction and securing heat insulation property using recycled wasted form polyurethane without any forming agents. A small quantity of admixture used for constructability and avoiding material segregation. We picked admixtures from two different companies which shows evenly dispersed of wasted form polyurethane. This research conducts a study on the effect of mixing ratio of admixture on the light-weight concrete used wasted form polyurethane. As a result of the test, increased mixing ratio of the admixtures results reduced fluidity of concrete. On the other hand, percentage of moisture content and compressive strength are increased slightly. Combustibility performance and sound insulation performance are also secured, as well.

• Journal of the Korean Society for Railway
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• v.16 no.1
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• pp.20-25
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• 2013

The frame elements of modern high speed trains are typically fabricated with extruded aluminum panels. However, the sound transmission loss (STL) of extruded aluminum panels is less satisfactory than flat panels with the same surface density. This study proposes a method for prediction of the sound transmission loss of extruded aluminum panels using finite element analysis. The panel is modeled by finite element analysis, and the STL is calculated using a measure of Sommerfeld radiation at the specimen surface, boundary conditions, and the internal loss factor of the material. In order to verify the validity of the predicted value, intensity transmission loss was measured on the aluminum specimen according to ASTM E2249-02. The proposed method of analysis will be utilized to predict the sound insulation performance of extruded aluminum panels for railway vehicles in the design stage, and to establish measures for their improvement.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2226-2228
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• 2005

High voltage induction motor is the important equipment for ensuring the driving performance of the electric train. PD(partial discharge) is a good indicator for showing the insulation performance of stator coil in HV induction motor. This paper has investigated the characteristics of PD occurrence aspects for both the sound and defective stator coil which consist of maximum PD amplitude(V), total occurrence number, average PD amplitude(V) and PD amplitude(v) - PD occurrence number(n). They were compared with each other depending on applied voltages and reconstructed to $60{\times}60$ matrices of PD amplitude(v)-occurrence phase (${\phi}$)-occurrence number(n) which is the good way to estimate the PD sources in stator coil.

• Composites Research
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• v.17 no.3
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• pp.15-22
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• 2004

Acoustic load generated by rocket propulsion system is one of major dynamic loads during lift-off phase so that it causes the structural failure and electronic malfunction of payloads. Acoustic loads can be greatly reduced by an appropriate acoustical design of nose faring structures. This paper deals with the acoustical design of the nose fairing structure for launch vehicle. It is well known that a honeycomb sandwich structure is a poor sound insulator because of its high specific stiffness. In this paper, the sound transmission characteristics of four kinds of honeycomb structures for noise fairing were investigated by means of numerical and experimental ways. In order to estimate transmission loss, infinite plate theory by Moore and Lyon and statistical energy analysis (SEA) method were used. The predicted results showed a good agreement with measured ones. These enabled us to determine a proper core material for nose fairing, which shows good sound insulation performance per weight.

• Environmental Engineering Research
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• v.20 no.4
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• pp.383-391
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• 2015

Transparent type noise barrier is a desirable facility since it provides a secure view to drivers and passengers. However, reflection from this type of barrier could annoy dwellers on the sides of the road. To reduce reflection noise by transparent type barrier, modification can be made to the shapes on the front side and hence get effects by distortion of sound transmission. To achieve this, we have conducted simulation by which the effects of patterned screens of noise barrier on high-ways were investigated. The reduction effects of reflected sounds were evaluated for swelling, swelling with curved, rectangular and V-shaped screen type barriers, compared to the planar panel. The emitting noise was generated by 6-lane road and the patterned noise barriers had shown the reduction effects, especially in swelling and swelling with curved type for middle height dwellers, and the V-shaped screen type for higher elevation dweller. The swelling-type showed a decrease of 0.7~1.2 dB, performing the best diminution effect among the tested noise barriers.

• Journal of Biosystems Engineering
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• v.40 no.3
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• pp.159-164
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• 2015

Purpose: Recently, environmental pollution and safety problems in agricultural production have become important issues. Initially, bio-production machines focused on high production efficiency rather than workers' safety and comfort, but this trend slowly has changed as time went on. Methods: This study was carried out to identify sound efficiently and reliably for noise reduction by using a combine cabin model. Ethylene propylene diene monomer (M-class) rubber (EPDM) was applied to improve noise reduction performance from parts connected directly to the front, rear, left side, and bottom side of the cabin. Results: As a result, an average noise reduction of 1.85 dB was achieved in the normal hearing range between 500 Hz to 2 kHz. Conclusions: Reducing the cabin noise levels can reduce a worker's fatigue, improve working environment, and contribute to future low-noise and high-quality cabin environment.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.1087-1092
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• 2006

Recently, traffic noise level is rapidly increasing, and it is crowed caused by recently overcrowded and overgrown cities, and increasing traffic volume is emerging as a major factor of disrupting the living and working environment. In this situation, citizens are increasingly complaining about the traffic noise. The noise level of in major cities in Korea is serious and affects on citizens physically and psychologically. Many people live in residential areas around crowed roads in major cities, such as Seoul. Accordingly, the purpose of this study is to predict outside noise distribution of building through survey and simulation to make better sound insulation performance research. The result of this study shows that the traffic noise is influenced from ground 50m and analyzed that form of building and arrangement type must be considered to the level of noise decrease.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.227-228
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• 2023

A floating floor generally consists of mortar bed separated from the structural RC slab by a continuous resilient layer. It is known that the floating floors are a type of vibration-isolation system to improve the impact sound insulation performance. However, some researchers have demonstrated that the amplification of vibration response at a specific range of frequencies results in an increase in the impact sound level. This study carried out the forced vibration tests to obtain the frequency response function (FRF) of a floating floor compared with a bare RC slab. Test results shows that the additional peak occur in vibrational spectrum of the floating floor except natural vibration modes of the bare RC slab. This is because the relatively flexible resilient material and mass of the mortar bed offer an additional degree of freedom in the structural system. Therefore, it could be efficient for reduction of floor impact vibration and noise to control the additional mode frequency and response of floating floors.