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Transactions of the Korean Society for Noise and Vibration Engineering
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Journal DOI :
The Korean Society for Noise and Vibration Engineering
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Volume & Issues
Volume 26, Issue 4 - Aug 2016
Volume 26, Issue 3 - Jun 2016
Volume 26, Issue 2 - Apr 2016
Volume 26, Issue 1 - Jan 2016
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Vibration and Acoustic Analysis of Balanced Armature Micro Speaker
Ko, Dong Shin ; Hur, Duk Jae ; Kwon, Sang Yup ; Lee, Sung Su ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 1, 2016, Pages 5~12
DOI : 10.5050/KSNVE.2016.26.1.005
This paper describes the development process for vibration and acoustic characteristics of a balanced armature speaker. The design parameters were chosen in consideration of the influence of the bending stiffness of balanced armature which is the form of a cantilever structure in the speaker. For study of the performance of the speaker according to the design parameters, in the first step, we analyzed the characteristics of the velocity of the diaphragm to the electrical input. Next step, acoustic characteristics were analyzed by structural-acoustic coupled analysis. And the reliability of the analysis was verified by comparing the result of analysis with test results. Finally, we proposed a design method for implementing an enhanced balanced armature speakers through analysis method.
Numerical Investigation of Serration Effect on the Helmholtz Resonance
Lee, Seungsoo ; Jeon, Minu ; Lee, Soogab ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 1, 2016, Pages 13~19
DOI : 10.5050/KSNVE.2016.26.1.013
The flow-excited Helmholtz resonance phenomenon was investigated numerically using Reynolds averaged Navier-Stokes approach. The fundamental cause of the Helmholtz resonance phenomenon is known as shedding of a single discrete vortex from orifice edge that travels during one period of the oscillation. In this study, serrated deflector, which is biomimetic design of the owl's feather, is used to split a single vortex into small vortices. Rectangular deflector and serrated deflector are compared with numerical results of pressure and streamline inside the cavity. Consequently, the serration breaks the shedding period of vortex core and eliminates the resonance. Also, it changes the flow pattern in according to the location of different serration height. By making inflows and outflows occur simultaneously in spanwise direction in the cavity, the period of Helmholtz resonance disappears. Comparing between rectangular deflector and serrated deflector, the serrated deflector can deal with the Helmholtz resonance more effectively.
Noise Characteristics of Air Cleaners and Humidifiers
Kim, Yong Hee ; Park, Ji Hoon ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 1, 2016, Pages 20~26
DOI : 10.5050/KSNVE.2016.26.1.020
This study investigated noise characteristics of air cleaners and humidifiers in terms of frequency domains and measurement directions. Noise levels of 31 air cleaners and 36 humidifiers were measured in an anechoic chamber according to the related group standards. As for air cleaners, 5 receiving points of 1 m off from front, rear, left, right and top surfaces of the product were considered. In case of humidifiers, 4 receiving points without the rear position were considered in the same manner as air cleaners. In each case, A-weighted equivalent continuous sound level was measured three times for 1 min. As a results, most of the measured air cleaners and humidifiers showed the highest noise levels at top directions due to the air ventilating location. In case of air cleaners, averaged noise levels of top and rear positions were 49.9 and 48.2 dB(A), respectively, whereas averaged noise level of other positions was all 45.2 dB(A). In case of humidifiers, averaged noise level of top position was 44.1 dB(A) whereas averaged noise levels of other positions were 38.7 to 39.1 dB(A). In addition, high frequency content of 1 kHz and 3.15 kHz to 4 kHz for air cleaners and middle frequency content of 500 Hz to 1.6 kHz for humidifiers showed significant contribution to determination of overall noise levels with correlation coefficient of 0.9 and above.
The Effect of Moving Mass on Resonance Phenomenon and Natural Frequency of a Simply Supported Beam
Min, Dong-Ju ; Jung, Myung-Rag ; Park, Sung-Min ; Kim, Moon-Young ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 1, 2016, Pages 27~38
DOI : 10.5050/KSNVE.2016.26.1.027
The purpose of this study is to investigate the influence of moving mass on the vibration characteristics and the dynamic response of the simply supported beam. The three types of the moving mass(moving load, unsprung mass, and sprung mass) are applied to the vehicle-bridge interaction analysis. The numerical analyses are then conducted to evaluate the effect of the mass, spring and damper properties of the moving mass on natural frequencies and dynamic responses of the simply supported beam. Particularly, in the case of the sprung mass, variations of the natural frequency of simply supported beam are explored depending on the position of the moving mass and the frequency ratio of the moving mass and the beam. Finally the parametric studies on the resonance phenomena are performed with changing mass, spring and damper parameters through the dynamic interaction analyses.
Turbulent-induced Noise of 2-dimensional Sonar Dome Shaped Structure
Choi, Yo-Seb ; Hong, Suk-Yoon ; Song, Jee-Hun ; Kwon, Hyun-Wung ; Choi, Woen-Sug ; Jung, Chul-Min ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 1, 2016, Pages 39~48
DOI : 10.5050/KSNVE.2016.26.1.039
The latest research has shown that the turbulence-induced noise is important in total characteristics of flow noise. Also, turbulence-induced noise have a significant influence for performance of sonar dome. In this paper, Flow analysis is performed on vicinity of the sonar dome model using Large Eddy Simulation method. Also, direct method that extracts perturbational sound pressure, FW-H method without turbulence-induced noise and permeable FW-H method that is able to calculate turbulence- induced noise were compared in order to show turbulence effect.
Study on a Development of the Prediction Equation of the Wind Power Plant Noise
Gu, Jinhoi ; Lee, Jaewon ; Lee, Woo Seok ; Jung, Sungsoo ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 1, 2016, Pages 49~54
DOI : 10.5050/KSNVE.2016.26.1.049
The wind power plants were installed in many places because of the low climate changing effects since 2000. Generally, the wind power plants located in the seaside and the mountainous area and the heights of the windmills are about 40 m~140 m above the ground level. So the noises emitted from the wind power plants propagate far away compared with other environment noise sources like trains and cars noise. Because of these reasons, the noise emitted from the wind power plant is easy to cause the additional social problems like as noise complaints. Under the situation, the ministry of environment has established the guideline to evaluate the environmental effects for the wind power plant. According to the guideline, the noise of the wind power plant has to meet 55 dB(A) at daytime and 45 dB(A) at night in the residential area, which is regulated in the noise and vibration management law. But, it is difficult to estimate the noise emitted from the wind power plant because of the absence of the prediction model of the wind power plant noise. Therefore, the noise prediction model for wind power plants using the regression analysis method is developed in this study. For the development of the model, the sound pressure levels of the wind power plants in Jeju island are measured and the correlations between the sound pressure levels are analyzed. Finally, the prediction equation of the wind power plant noise using by regression analysis method derived. The prediction equation for the wind power plant noise proposed in this study can be useful to evaluate the environmental effects in any wind power plant development district.
Vibration Simulation Using LuGre Friction Model for Cladding Tube Fretting Wear Analysis
Park, Nam-Gyu ; Kim, Jin-Seon ; Kim, Joong-Jin ; Kim, Jae-Ik ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 1, 2016, Pages 55~62
DOI : 10.5050/KSNVE.2016.26.1.055
Nuclear fuels are always exposed to hot temperature and high speed coolant flow during the reactor operation. Thus the fuel rod accompanies small amplitude vibration due to the turbulent flow. The random vibration causes friction between the fuel rod and the grid structure which provides the lateral supports. The friction is critical to the fuel rod fretting wear, and it degrades fuel performance when a severe wear is developed. LuGre friction model is introduced in the paper, and the performance was evaluated comparing to the classical Coulomb model. It is shown that the developed friction force considering the Coulomb friction is not enough to stop or delay the motion while the stick-slip can be simulated using LuGre friction model. Numerical solutions of the two dimensional spacer grid cell model with the modern friction are also reviewed, and it is discussed that the new friction model simulates well the nonlinear mechanism.
A Study on Deploying Time of Active Hood Lift System of Passenger Vehicles with Principal Design Parameters
Lee, Tae-Hoon ; Yoon, Gun-Ha ; Choi, Seung-Bok ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 1, 2016, Pages 63~68
DOI : 10.5050/KSNVE.2016.26.1.063
This research investigates the deployment time of an active hood lift system(AHLS) activated a gunpowder actuator for the passenger vehicle. The deployment time of the system is investigated by changing the principal design parameters of the system. In order to achieve this goal, after introducing the geometric structure and operating principle of the AHLS, the dynamic equations of the system are formulated for deploying motion. Subsequently, using the dynamic equations, the deployment time of the system is determined by changing several geometric design parameters such as location of actuator. It is then identified which design parameters are main factors to affect the deployment time of AHLS.
An Accuracy Improvement Method on Acoustic Source Localization Using Ground Reflection Effect
Go, Yeong-Ju ; Choi, Donghun ; Lee, Jaehyung ; Choi, Jong-Soo ; Ha, Jae-Hyoun ; Na, Taeheum ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 1, 2016, Pages 69~74
DOI : 10.5050/KSNVE.2016.26.1.069
A technique for improving estimation accuracy is introduced in order to locate the impact position of artillery shell during the weapon scoring test. Study on localization of impacts using acoustic measurement has been conducted and the usability of sensor array is verified with experiments. When the blast occurs above the ground in the firing range, the acoustic sensor above the ground can measure the directly propagated sound with the ground-reflected one. In this study, a method for reducing estimation error by using the reflection signal measurements based on the time difference of arrival method. Considering the reflection sound works as same as placing a virtual sensor symmetrically through the ground. This idea enables a virtual three-dimensional array configuration with a two-dimensional plane array above the ground as such. The time difference between the direct and the reflected propagations can be estimated using cepstrum analysis. Performance test has been made in the simulation experiment in the football size area.
Exact Solution for Bending Vibration of Rotating Cantilever Beam with Tapered Width Using Transfer Matrix Method
Lee, Jung Woo ; Kwak, Jong Hoon ; Lee, Jung Youn ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 1, 2016, Pages 75~81
DOI : 10.5050/KSNVE.2016.26.1.075
In this study, a transfer matrix method in which can produce an infinite number of accurate natural frequencies using a single element for the bending vibration of rotating Bernoulli-Euler beam with linearly reduced width, is developed. The roots of the differential equation in the proposed method are calculated using the Frobenius method in the power series solution. To demonstrate the accuracy of the method, the calculated natural frequencies are compared with the results given by using the commercial finite element analysis program(ANSYS), and the comparison results between these two methods show the excellent agreement. Based on the comparison results, a parametric study is performed to investigate the effect of the centrifugal forces on the non-dimensional natural frequencies for rotating beam with the variable width.
Performance Evaluation of a Semi-active Vehicle Suspension Using Piezostack Actuator Valve
Han, Chulhee ; Yoon, Gun-Ha ; Park, Young-Dai ; Choi, Seung-Bok ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 1, 2016, Pages 82~88
DOI : 10.5050/KSNVE.2016.26.1.082
This paper proposes a new type of semi-active direct-drive valve(DDV) car suspension system using piezoelectric actuator associated with displacement amplifier. As a first step, controllable piezoelectric DDV damper is designed and governing equation of a quarter-vehicle suspension system consisting of sprung mass, spring, tire and the piezostack DDV damper is constructed. After deriving the equations of the motion, in order to control spool displacement and damping force the skyhook controller is designed and applied. The performance evaluation of the proposed semi-active suspension system is conducted with different displacement of spool. Then, the ride comfort analysis is undertaken in time domain with bump road profile.
Study on Error Correction of Impact Sound Position Estimation Using Ray Tracing
Choi, Donghun ; Go, Yeong-Ju ; Lee, Jaehyung ; Na, Taeheum ; Choi, Jong-Soo ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 1, 2016, Pages 89~96
DOI : 10.5050/KSNVE.2016.26.1.089
TDOA(time delay of arrival) position estimate from acoustic measurement of artillery shell impact is studied in order to develop a targeting evaluation system. Impact position is calculated from the intersections of hyperbolic estimates based on the least square Taylor series method. The mathematical process of Taylor series estimation is known to be robust. However, the concern lays with the accuracy because it is sensitive to the bias caused by the randomness of measurement situation. The measurement error typically occurs from the distortion of waveform, change of travelling path, and sensor position error. For outdoor measurement, a consideration should be made on the atmospheric condition such as temperature and wind which can possibly change the trajectories of rays of sound. It produces wrong propagation time events accordingly. Ray tracing and optimization techniques are introduced in this study to minimize the bias induced by the ray of sound. The numerical simulation shows that the atmospheric correction improves the estimation accuracy.
A Study on Interior Noise Contribution Analysis of Trains based on OTPA Method
Jung, Jae-Deok ; Hong, Suk-Yoon ; Song, Jee-Hun ; Kwon, Hyun-Woung ; Noh, Hee-Min ; Kim, Jun-Kon ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 1, 2016, Pages 97~103
DOI : 10.5050/KSNVE.2016.26.1.097
The sensitivity of interior noise that the passengers perceive is comparatively high in the train, and structure-borne and air-borne types of noises come into the train. In this paper, to analyze contributions of these noise sources operational transfer path analysis(OTPA) is used. OTPA has some advantages of executing the contribution rates of several sources simultaneously, and in this work, 29 points are measured while running. Transfer functions between reference measurement points and response measurement points are calculated by the singular value decomposition(SVD) and Principal component analysis(PCA) method, and the frequency characteristics of the noise source are successfully derived. Also the interior noise is predicted and compared with measurement data to show the reliability.
Study on the Development of Noncontact Vibration Exciter for Thin Plates Using Magnetism
Hur, Kwan-Do ; Son, In-Soo ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 1, 2016, Pages 104~109
DOI : 10.5050/KSNVE.2016.26.1.104
The noncontact vibration exciter system using the electro-magnet for a thin plate is studied in this paper. Based on the Euler-Bernoulli beam theory, the equation of motion of thin plate is derived. The main purpose of this experiment is to match the input-frequency and response frequency of thin plate. The test equipment is configured to vibrate on both sides of the thin plate using the electro-magnet. Two frequencies(input frequency and response frequency) in our experiments show very good agreement. This study results will contribute to basic investigate of an alternative air-knife system for the steel industry.