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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
The Journal of the Acoustical Society of Korea
Journal Basic Information
Journal DOI :
The Acoustical Society of Korea
Editor in Chief :
Volume & Issues
Volume 8, Issue 5 - Oct 1989
Volume 8, Issue 4 - Aug 1989
Volume 8, Issue 1 - Feb 1989
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A Study on the Characteristics of the Parameters for the Statistical Analysis of Vibration Signal by Using Bearing Wear Test
Jun, Oh-Sung ; Hwang, Cheol-Ho ; Yoon, Byung-Ok ; Eun, Hee-Joon ;
The Journal of the Acoustical Society of Korea, volume 8, issue 1, 1989, Pages 5~12
This paper is concerned with the characteristics on the statistical parameters of vibration signal from bearing with changing its operating conditions as well as the spreading of faults. The rms, Kurtosis, crest factor, probability of exceedance and probability density function have been chose as the statistical parameters. To characterize of each, vibration signals have been recorded from four ball tester at different loads, operation speeds and time. The values of the statistical parameters for each frequency band have been calculated after A/D conversion and digital filtering of the recorded signals. It has been found that unlike rms values the statistical parameters such as Kurtosis etc. are almost unchanging with the change of the operating conditions such as load and speed. This suggests that the statistical parameters may be used for determining the development of faults independent of the operating conditions. In fact, the statistical parameters deviate considerably from their respective normal values when the faults developed under load conditions in the samples, conforming the suggestion.
A Study on Piano String Vibration
Kang, T.-H. ; Yoon, Y.-K. ; Lee, S.-J. ;
The Journal of the Acoustical Society of Korea, volume 8, issue 1, 1989, Pages 13~22
This study made an analysis of the characteristics of vibration & tone color of the piano strings on which a concentrated mass was set to give variety of different variations to the gamut. Theoretical analyses in this study were based on discrete and continuous system, of which the former was transformed into a multi-degree of freedom system by dividing into a number of small parts, while the latter utilized mode summation and Laplace transformation methods. And experiments were carried out with setting concentrated masses on upright piano string.
Pressure Wave Propagation Phenomena in Water Containing Uniformly Distributed Gas Bubbles
Kim, D.-H. ;
The Journal of the Acoustical Society of Korea, volume 8, issue 1, 1989, Pages 23~30
Propagation phenomena of nonlinear pressure waves in a bubbly mixture are studied. The governing equations for a bubbly mixture are derived heuristically and energy equation is incorporated with other governing equations to take thermal effects into consideration inside the bubble. This non-isothermal condition of the bubble inside is especially important when high amplitude pressure waves are treated. Keller's equation is adapted for the bubble dynamics as practical problem. Some numerical simulations are carried out for the shock tube problem using a computer program based on the above model. A comparison with experimental results of Noordzij and van Wijngaarden shows that the structure of the wave in the shock tube experiment seems to be much more significantly affected 요 the complex heat transfer phenomena inside the bubbles than by the relative translational motion between bubbles and surrounding liquid.
Optimal Viscoelastic Layered Dynamic Vibration Absorber
Im, Seong-Dae ; Lee, Si-Bok ;
The Journal of the Acoustical Society of Korea, volume 8, issue 1, 1989, Pages 31~37
The effectiveness of using a composite beam with constrained visco-elastic layer as a dynamic vibration absorber is investigated. The performance of this absorber is evaluated in terms of displacement transmissibility when to a primary beam with built-in ends and compared to that of the uniform beam absorber. The results of analysis and design show that it is possible to suppress simultaneoulsy the peak transmissibilities at two or more resonance frequencies and the optimal parameters are located within the available viscoelastic material properties.
Optimal Mounts Design for a Rotation Machine on a Flexible Plate
Kim, Joon-Yeop ; Lee, Si-Bok ;
The Journal of the Acoustical Society of Korea, volume 8, issue 1, 1989, Pages 38~47
The optimal mounting system for reciprocating comperssor supported on a flexible is designed. Four short hollow rubber cylinders are used as mounting pads, and so the thickness, diameter, height and location of the rubber mounts are considered as design parameters. The optimal mounts parameters which give the smallest force transmittance, are obtained by Constrained Rosenbrock Method.
Noise Control Requirements for Airport
Ok, C.-K. ; Joo, S.-D. ;
The Journal of the Acoustical Society of Korea, volume 8, issue 1, 1989, Pages 48~58
Airplane noise become a serious problem today. Using the noise patterns at KIMPO and CHEJU INTERNATIONAL AIRPORTS, the impact area of noise for the newly planned international airport was predicted. Contours for noise level were made by a plotter based on WECPNL estimated by a computer program with basic noise data for FAA requirement. The result was also compared with the noise control level abroad.
The Characteristics of HVAC Noise in Office Buildings
Do, Young-Ju ; Kim, Dong-Gyu ; Kim, Heung-Sik ;
The Journal of the Acoustical Society of Korea, volume 8, issue 1, 1989, Pages 59~66
This study aims to provide the basic data useful in assessing indoor-noise and designing sound devices in office buildings of HVAC system. The measurements of HVAC noise were carried out in office room and mechanical room. The performance of absorptive chamber and side branch was also estimated in the office buildings which have HVAC noise problems. The results of experiments show that the NR value of indoor HVAC noise is rather higher than that of ISO recommendations at the frequencies below 500Hz. In addition, the results indicated that the absorptive chamber attenuates noise over broad band frequencies and side branch reduces noise at the special resonant frequency.
Measurement of Complex Sound Pressure Reflection Coefficient Using Standing Wave Tube
Suh, Sang-Joon ; Jho, Moon-Jae ; Kim, Youn-Soo ;
The Journal of the Acoustical Society of Korea, volume 8, issue 1, 1989, Pages 67~74
The reflection coefficients of the sound absorbing materials are obtained from the standing wave ratio in the standin wave tube. This method is rather laborious to find the sound pressure maximum and minimum. We devised new method for determination of the complex reflection coefficients of the materials. The sound pressures and the phases are measured at least three points along the axis of the tube. The complex reflection coefficients are determined from the measured values by least square method. The measured results for the glasswool with thickness of 5cm and density of
and the steel plate with thickness of 1.5cm are in good agreement with those of the conventional method. It is possible to measure the complex reflection coefficients at low frequencies with short standing wave tube and to interface with the personal computer which is very useful for the handling of amount of samples.
Signal Stabilization of Optical Fiber Acoustic Sensor Using a Cylindrical Piezoelectric Stretcher
Lee, D.-H. ; Jho, M.-J. ; Suh, S.-J. ; Eun, H.-J ;
The Journal of the Acoustical Society of Korea, volume 8, issue 1, 1989, Pages 75~80
A Mach-Zehnder interferometer using single mode optical fiber was constructed which operates in homodyne detection scheme. Its response to air-borne soun pressure was examined experimentally. A signal stabilizer was developed for maintaining optical fiber interferometer in quadrature condition using a cylindrical piezoelectric stretcher. This maintains the optical fiber sensor at a maximum sensitivity in the presence of the phase drift caused by temperature fluctuation and other types of environmental disturbances.
Korean Phoneme Recognition Using duration-dependent 3-State Hidden Markov Model
Yoo, H.-C. ; Lee, H.-J. ; Park, B.-C. ;
The Journal of the Acoustical Society of Korea, volume 8, issue 1, 1989, Pages 81~87
This paper discribes the method associated with modeling of Korean phonemes. Hidden Markov models(HMM's) may be viewed as an effective technique for modeling the inherent nonstationarity of speech signal. We propose a 3-state phoneme model to represent the sequentially changing characteristics of phonemes, i.e., transition-to-stationary-to-transition. Also we clarify that the duration of a phoneme is an important factor to have an effect in recognition accuracy and show that improvement in recognition rate can be obtained by using duration-dependent 3-state hidden Markov models.