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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of the Korean Society for Noise and Vibration Engineering
Journal Basic Information
Journal DOI :
The Korean Society for Noise and Vibration Engineering
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Volume & Issues
Volume 21, Issue 12 - Dec 2011
Volume 21, Issue 11 - Nov 2011
Volume 21, Issue 10 - Oct 2011
Volume 21, Issue 9 - Sep 2011
Volume 21, Issue 8 - Aug 2011
Volume 21, Issue 7 - Jul 2011
Volume 21, Issue 6 - Jun 2011
Volume 21, Issue 5 - May 2011
Volume 21, Issue 4 - Apr 2011
Volume 21, Issue 3 - Mar 2011
Volume 21, Issue 2 - Feb 2011
Volume 21, Issue 1 - Jan 2011
Selecting the target year
Evaluation for Noise Reduction of the HVAC by Modification of CAM Curve
Jeong, J.E. ; Jung, C.Y. ; Seo, B.J. ; Jeong, U.C. ; Oh, J.E. ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 21, issue 9, 2011, Pages 787~797
DOI : 10.5050/KSNVE.2011.21.9.787
The noise in a vehicle is an important factor for customers purchasing a car. Particularly, reduction of the noise that is generated from HVAC(heating, ventilation and air conditioning) is very important since it has considerable effects on interior noise. In general, identification of noise source is crucial to reduce noise level. The complex acoustic intensity method is widely used to obtain the accurate measurement and identification of noise source. Therefore, in the previous study, noise source of HVAC was identified through experimental approach using the complex acoustic intensity method. In this study, we are intended to confirm reduced level of noise by comparing the result between before and after modification of cam curve that is based on identified noise source of HVAC. It is found out that noise source of HVAC are motor and cam area using the complex acoustic intensity method in the previous study. We performed experiments to compare noise level between before and after modification of cam curve. Especially, it can be seen that complex acoustic intensity method using both active and reactive intensity is vital in devising a strategy for comparison to noise level. Also, the vector flow of acoustic intensity was investigated to identify sound intensity distributions and energy flow in the near field of HVAC.
A Study on an Optimal Spot-weld Layout Design for a Shock Tower Structure Considering the Fatigue Life under Random Vibration Loads
Lee, Yong-Hoon ; Lee, Seung-Yoon ; Bae, Bok-Soo ; Lee, Sang-Beom ; Yim, Hong-Jae ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 21, issue 9, 2011, Pages 798~804
DOI : 10.5050/KSNVE.2011.21.9.798
In this paper, optimal spot weld layout design for a shock tower structure is presented. This design increases the fatigue life of the spot-welds thereby increasing the fatigue life of the shock tower itself. In order to predict the fatigue life, a quasi-static analysis has been conducted then a fatigue analysis was performed through the application of random vibration loads. In order to optimize the spot weld layout, the design variables that have an effect on the spot weld fatigue life were determined. A spot weld fatigue analysis was then conducted based on the experiment design. Finally, a response surface model was made using the fatigue analysis results and an optimized spot weld layout model, one that increases the fatigue life of the spot welds and thereby the fatigue life of the shock tower, was developed.
Experimental Studies for Analysing of Characteristics of Floor Impact Sound through a Scale Model with Box-frame Type Structure
Yoo, Seung-Yup ; Jeon, Jin-Yong ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 21, issue 9, 2011, Pages 805~812
DOI : 10.5050/KSNVE.2011.21.9.805
This study investigated the characteristics of heavy-weight floor impact sounds of box-frame type structure using 1:10 scale model. Ten types of floor structures(bare slabs and floating floors) were evaluated in terms of dynamic stiffness and loss factor. Floor vibrations and radiated sounds generated by simulated impact source were also measured. The results showed that the bakelite was appropriate for simulating concrete slab in the 1:10 scale model, and surface velocity and sound pressure level of concrete slab measured from the scale model showed similar tendencies with the results from in-situ in frequency domain. It was also found that dynamic behaviors of layered floor structures in the 1:10 scale model were similar to those in a real scale. Therefore, the use of 1:10 scale model would be useful for evaluating the heavy-weight floor impact sound insulation of layered floor structures when the frequency-dependent dynamic properties of each material are known.
Nonlinear Dynamic Response of Cantilevered Carbon Nanotube Resonator by Electrostatic Excitation
Kim, Il-Kwang ; Lee, Soo-Il ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 21, issue 9, 2011, Pages 813~819
DOI : 10.5050/KSNVE.2011.21.9.813
This paper predicted nonlinear dynamic responses of a cantilevered carbon nanotube(CNT) resonator incorporating the electrostatic forces and van der Waals interactions between the CNT cantilever and ground plane. The structural model of CNT includes geometric and inertial nonlinearities to investigate various phenomena of nonlinear responses of the CNT due to the electrostatic excitation. In order to solve this problem, we used Galerkin`s approximation and the numerical integration techniques. As a result, the CNT nano-resonator shows the softening effect through saddle-node bifurcation near primary resonance frequency with increasing the applied AC and DC voltages. Also we can predict nonlinear secondary resonances such as superharmonic and subharmonic resonances. The superharmonic resonance of the nano-resonator is influenced by applied AC voltage. The period-doubling bifurcation leads to the subharmonic resonance which occurs when the nano-resonator is actuated by electrostatic forces as parametric excitation.
Active Window to Reduce the Exterior Noise Flowed Through the Open Window
Kwon, Byoung-Ho ; Park, Young-Jin ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 21, issue 9, 2011, Pages 820~827
DOI : 10.5050/KSNVE.2011.21.9.820
Recently, noise has been regarded as one of the most notorious and frequent environmental pollutions which can be often encountered not only in the living space but also in the industrial site. Studies on physiological and psychological effects of long-term noise exposure to human being have commanded the public interest on noise issues. Since environmental noises such as traffic noise and construction noise is mainly flowed through the open window, it is necessary to develop the active noise control system to reduce it inside the building. Although control speakers and microphones for the noise signal measurement in the control region are essential for the conventional active noise control methods, it is impossible to implement them in the control region in the building environment because the control region is the living quarter and they may hinder activities of the residents. Therefore, we proposed the active window system to reduce the exterior noise flowed through the open window with microphones installed outside the window and control speakers installed at the frame of the window. To confirm the performance of the proposed active window, we carried out the simulation and experiment using active window system with 8 control speakers. Simulation results showed the noticeable noise reduction effect inside the control region within the frequency range without the spatial aliasing. Experimental result showed that the total acoustic potential energy inside the room of the scale model is reduced to about 10dB within the interest of frequency range.
An Experimental Study on Micro-vibration Measurement Methods of a Reaction Wheel
Kim, Dae-Kwan ; Oh, Shi-Hwan ; Lee, Seon-Ho ; Yong, Ki-Lyuk ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 21, issue 9, 2011, Pages 828~833
DOI : 10.5050/KSNVE.2011.21.9.828
A reaction wheel assembly(RWA) is the largest disturbance source that can induce high frequency micro-vibration on an optical payload of satellites. To ensure a tight pointing-stability budget of satellites, the RWA disturbance effect on spacecraft should be accurately analyzed and evaluated for whole design phases. For this purpose, the micro-vibration disturbance of RWA should be precisely measured. In the present study, two measurement methods on RWA micro-vibration disturbances are compared and investigated. One is a free run-down speed test and the other is a constant speed test. The micro-vibration data measured by the two methods are analyzed in terms of spectrum characteristics, static and dynamic imbalance values, and root sum square(RSS) values. The analysis results show that both methods can measure very similar results in time and frequency domains and that the free run-down speed method is more adequate in respects to wheel friction modeling, noise rejection of imbalance and RSS peak evaluation.
Estimation of Vibration Source and Sound Radiation of a Refrigerator Fan by using Measured Acceleration Signals
Jung, Byung-Kyoo ; Jeong, Weui-Bong ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 21, issue 9, 2011, Pages 834~841
DOI : 10.5050/KSNVE.2011.21.9.834
Obtaining the real exciting force is important for the analysis of structural vibration or sound radiation to represent the actual condition. But in most cases, it is so difficult to get the actual force signals by direct measurement using sensors due to complex geometry. This paper suggests advanced source identification method which can be applied to the prediction of radiated noise considering correlations between measured signals. This method was implemented to the identification of the fan force in the refrigerator. The analysis of structural vibration and radiated noise caused by the fan force was also performed. The comparison between predicted SPL and measured SPL of the radiated noise by the refrigerator fan showed good agreement.
Characteristics of Sound Response in Ear Canal of Human and Reproduction of Acoustical Space
Ahn, Tae-Soo ; Lee, Doo-Ho ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 21, issue 9, 2011, Pages 842~849
DOI : 10.5050/KSNVE.2011.21.9.842
The human ear canal amplifies the sound pressure level at specific frequency bands. The characteristics of the ear canal are very similar to those of curved cylindrical tube. In this study, the characteristics of sound transfer in human ear canal were measured and the acoustical space of ear canal was reproduced from the canal cavity geometry. For the measurement of sound transfer function in ear canal, a probe microphone and a reference microphone were used. The sound transfer functions were measured for 5 human subjects. To reproduce the acoustical space of the ear canal, two kinds of ear simulator were designed. The first one is a straight cylindrical tube type and the other is a real-shape ear of which geometry was taken from a micro-CT scanning of a human ear. The characteristics of the reproduced apparatus were compared with those of the human and a commercial ear simulator, RA0045 of G.R.A.S. Inc. The comparison results show that the developed apparatus well represent the ear canal characteristics in the low frequency, but have limited coincidence in level over high frequency range.
The Study on Improvement of Acoustic Performance for Automobile Sound-absorbing Materials Using Hollow Fiber
Lee, Jung-Wook ; Lee, Su-Nam ; Shim, Jae-Hyun ; Jung, Pan-Ki ; Lee, Won-Ku ; Bang, Byoung-Joo ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 21, issue 9, 2011, Pages 850~857
DOI : 10.5050/KSNVE.2011.21.9.850
Generally, sound-absorbing materials in vehicles are used for giving the comfort to passengers by reducing noise while driving. Materials of which targets are light weight, high performance, eco friendliness and recycling have been developed recently. In this study, sound-absorbing materials using PET(polyethylene terephthalate) hollow fibers to achieve the light weight and the high sound absorption performance are developed, and then evaluated to meet a requirement for the automotive components. The test results show that the acoustic performances of developed products having new fiber structure are better than those of the conventional product.
Examination on Active Pneumatic Vibration Isolation Table with Moving Masses on It by Time Delay Control
Shin, Yun-Ho ; Moon, Seok-Jun ; Chung, Jung-Hoon ; Kim, Byung-Hyun ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 21, issue 9, 2011, Pages 858~867
DOI : 10.5050/KSNVE.2011.21.9.858
As applying an active control technique to a pneumatic vibration isolation system, the settling time for the payload excitation could be remarkably reduced as well as the improvement of isolation performance for the ground vibration. Some previous researches were dealt with the settling time through the simulation or experiment but, the discussion on the simulation or experimental results including moving parts, such as a XY-stage, on the isolation table rarely exists. As considering the moving part, the dynamic model could be time varying system and in such a case the force imposed on pneumatic vibration isolation table could be described by inertial forces of moving parts according to Newton`s 3rd law, the action and reaction law. In this paper, the simulation procedure of the 3-DOF active pneumatic vibration isolation system including moving parts by TDC(time delay control) technique is proposed and the effectiveness through simulation results are also shown.