• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2020년도 봄 학술논문 발표대회
• /
• pp.10-11
• /
• 2020

Currently, the most used forms, such as euro form and aluminum form, has many problems. There are issues with noise of construction site because of existing forms' material and issues with safety because of heavy weight. To solve these problems, there are many researches on using plastic and composite materials on the formwork. However, plastic has lower tensile strength than the steel and aluminum and composite materials are expensive. Therefore, constructors are avoid to use the forms with new materials. The purpose of this study is to develop light-weight plastic form to solve these existing problems by using ABS with optimized design. To verify, the study measured the amount of deflection from developed form through a load test. The test result showed a deflection of 1.15mm when 1.4ton was loaded in the middle of form. The result of the study verified that the usage of ABS and optimized design effectively reduced the weight and noise. Also, it's performance was verified through the load test.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
• /
• pp.634-637
• /
• 1997

This paper is on the research and development of new SIV(Static Inverter) using IGBT(Insulated Gate Bipolar Transistor) semiconductor for a wide range of electric railway applications. For the simplification and higher controllability, the direct PWM control method with 3level inverter topology was adopted. In the new SIV system, the cost as well as bulk and weight was appreciably reduced about 40% lower than those of conventional SIV, the electrical efficiency was increased above 95% and the audible noise level was less than 65dB. In addition, the THD(Total Harmonic Distortion) factor was below 5% and the voltage fluctuation on a transient state was below 10%.

• 한국소음진동공학회논문집
• /
• 제24권6호
• /
• pp.483-492
• /
• 2014

Uncomfortable feelings of occupants by indoor floor impact noise in a residential building are not accurately represented by the floor impact noise from a standard impact source. It is due to the characteristics of standard impact sources, which are different from the impact forces produced by occupants. It varies significantly by impact source, and it is not easy to be replicated for testing. As a result, the indoor floor impact noise under different acoustic conditions cannot be directly compared. Using frequency response function(FRF), which represents the input-output relationships of a dynamic system, it is possible to examine the characteristics of the system. Especially, FRF can predict the response of a linear dynamic system subjected to various excitation. To determine the relationship between impact force and the corresponding response of dynamic system in residential building, the acceleration response of a concrete slab and the floor impact noise in the living room, produced by bang-machine and rubber-ball excitation, were measured. The test results are compared to the estimates based on FRF and impact force spectrum.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2004년도 추계학술대회논문집
• /
• pp.261-264
• /
• 2004

Impact sounds, such as those created by footsteps, the dropping of an object or the moving of furniture, can be a source of great annoyance in residential buildings. The character and level of impact noise generated depends on the object striking the floor, on the basic structure of the floor, and on the floor covering. This study base on the evaluate of isolation performance of impact sound according to the installation of ceiling and wall. In this test, we measured the reduction of impact sound in the case of inserting absorption materials, increasing of the thickness of air layer and using anti-vibration rubber in ceiling, install of absorption materials in wall. The results of this study show that treatment of ceiling and wall have some reduction of the light weight impact sound and heavy weight impact sound.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 추계학술대회논문집
• /
• pp.932-937
• /
• 2003

In apartment buildings, floor-impact sound has bean regarded as the major source which induces complaints from residents. It is mainly due to the use of light-weight structures. The vibration produced by impact on one part of an apartment building would travel as far as the other parts of structure with a little alleviation. As a result, the impact sound from upstairs has been regarded as a main source of noise causing discontentment among accupants. This study was carried out to measure the floor-impact sound levels and evaluate the insulation performance of floor-impact sound for seven apartment buildings. The floor-impact sound levels were measured for seventeen On-dol floor structures and various factors which influence the floor-impact sound were analyzed.

• Current Optics and Photonics
• /
• 제7권6호
• /
• pp.683-691
• /
• 2023

A typical terahertz time-domain spectroscopy system requires large, expensive, and heavy hardware such as a lock-in amplifier and a function generator. In this study, we replaced the lock-in amplifier and the function generator with a single sound card built into a typical desktop computer to significantly reduce the system size, weight, and cost. The sound card serves two purposes: 1 kHz chopping signal generation and raw data acquisition. A unique software lock-in (Python coding program to eliminate noise from raw data) method was developed and successfully extracted THz time-domain signals with a signal-to-noise ratio of ~40,000 (the intensity ratio between the peak and average noise levels). The built-in sound card with the software lock-in method exhibited sufficiently good performance compared with the hardware-based method.

• KIEAE Journal
• /
• 제9권4호
• /
• pp.23-28
• /
• 2009

Standard sound source currently used in heavy-weight floor impact sounds that cause many social problems has excessive low-frequency energy within a range from 63 Hz to 125 Hz, and is difficult to evaluate and measure. To solve these problems, studies are widely performed using a new impact source, the impact ball. In this study, the sound fields in a receiving room were compared and analyzed according to the current impact source, the bang machine, and the impact ball. And deviation of sound pressure level according to the impact source positions were compared. In case of impact ball, the sound pressure level was lower at 63 Hz and below and higher at 125 Hz and above. The same trend was observed at the low-frequency range on the horizontal and vertical planes, regardless of the type of the impact source, which showed the influence of the room mode. There was a problem with the variations in the sound pressure level according to the size or shape of the receiving room. And it also shows that change of source positions may effect the single number rating scheme.

• 전기학회논문지
• /
• 제61권1호
• /
• pp.179-185
• /
• 2012

Since the eco-era is getting closer, the importance of noise reducing in the passenger cars of high-speed train is very important. The active noise control is best choice to reduce low frequency noise because the passive one is too heavy for high speed trains where weight is so critical. Also ANC is able to reduce the ambient noise when the environmental-factor changes. To reduce a three-dimensional closed-space sound field like a car of a high-speed rail is hard to do using single channel ANC control system. We used multi-channel FXLMS algorithm which calculation speed is fast and the secondary path estimation is possible in order to take into account the physical delay in electro acoustic hardware control loudspeaker and power amplifier. Firstly, we have measured interior noise of KTX and estimated noise path in KTX test-bed. However there was some problem related to algorithm divergence and increasing the filter order. We have made a simulation of interior environment of KTX car by using three frequency bands of 120Hz, 280Hz, 360Hz as the most important for KTX ANC system. During this research the interior noise reduction of KTX car was made by using the multi-channel FXLMS algorithm. Reduction performance was evaluated and compared each other for open space section and tunnel section. in-situ experiment for the KTX noise reduction by proposed ANC was performed based on data obtained in simulation and they were compared for open space section and tunnel section as well.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2008년도 춘계학술대회논문집
• /
• pp.17-20
• /
• 2008

To develop floor impact sound resilient materials of apartment house effectively, floor impact sound insulation performance test lab. was designed and constructed in T company. Introducing specification and basic performance of this lab. could be helpful in plan and design of another lab. Floor space size of this lab. is $4.2m{\times}5.5m$ and this size is similar with that of living room of usual apartment house's (about $100m^2$) and the height of lab. is 2.4m. Slab thickness is designed by 180mm. Frequency characteristics is similar to general apartment house. Reverberation time of sound receiving room displays 1.26sec in 125Hz by establishing sound-absorbing materials. For light weight impact sound insulation performance of concrete bare floor structure is estimated by $L_{i,AW}\;=\;73$ and for heavy weight is estimated by $L_{i,Fmax,AW}\;=\;50$. Sound pressure level distribution of sound receiving room is ranged very uniformly. With these results, floor impact sound resilient materials could be evaluated and the results could be trusted by comparison tests.

• 한국소음진동공학회논문집
• /
• 제23권3호
• /
• pp.218-225
• /
• 2013

Vertically-launched missiles are supported as erected vertically in the vertical launching system of warship, and they should be mounted in the same way when vibration-tested. However, mounting missiles vertically makes a fixture, which is a supporting structure, bulky and heavy so requiring a high-performance exciter. Mounting missiles as laid down horizontally in a vibration test is economical regarding fixture manufacturing and exciter performance, but it makes test results incorrect because the different mounting direction has effects on the test results. A bending moment due to missiles' weight happens to missiles, and resilient mounts, which support missiles in the vertical launch system, deflect differently from the real situation because of the static deflection of these mounts due to missiles' weight. If the resilient mounts supporting missiles have nonlinear force-deflection characteristics, vibration test results become more different from the true results. This paper proposes to support missiles with an additional resilient mount such as a bunge code in order to solve those problems coming from mounting vertically-launched missiles as laid down horizontally in vibration tests. The proposed approach enables to obtain the same test results as in their actual mounting condition even though vertically-launched missiles are mounted in a different direction.