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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Journal of the Acoustical Society of Korea
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Journal DOI :
The Acoustical Society of Korea
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Volume & Issues
Volume 33, Issue 6 - Nov 2014
Volume 33, Issue 5 - Sep 2014
Volume 33, Issue 4 - Jul 2014
Volume 33, Issue 3 - May 2014
Volume 33, Issue 2 - Mar 2014
Volume 33, Issue 1 - Jan 2014
Selecting the target year
Empirical Prediction of Acoustic Load of Launch Vehicle Including Jet Impingement
Park, Seoryong ; Lee, Kyuho ; Kong, Byunghak ; Kang, Kyung Tai ; Jang, Seokjong ; Lee, Soogab ;
The Journal of the Acoustical Society of Korea, volume 33, issue 3, 2014, Pages 153~162
DOI : 10.7776/ASK.2014.33.3.153
Empirical prediction method of the acoustic load on the fairing is based on jet experimental data on the basis of similarity principle. Representative empirical prediction method, DSM-II(Distributed Source Method-II), is a distributing source method along the jet plume. But the empirical prediction model is limited to reflect the impingement source in real environment because it is based on the free jet data. So, we propose a empirical prediction method considering the impinging jet effect by adding a impingement source in the existing prediction method. Considering the additional source`s displacement, spectrum, strength and directivity, we calculate the acoustic load on the KSR-III(Korean Sounding Rocket-III) rocket and compare the results with the existing method and experiment data.
Development of Range-Dependent Ray Model for Sonar Simulator
Jung, Young-Cheol ; Lee, Keunhwa ; Seong, Woojae ; Kim, Hyoung-Rok ;
The Journal of the Acoustical Society of Korea, volume 33, issue 3, 2014, Pages 163~173
DOI : 10.7776/ASK.2014.33.3.163
Sound propagation algorithm for a sonar simulator is required to run in real-time and should be able to model the range and depth dependence of the Korean ocean environments. Ray model satisfies these requirements and we developed an algorithm for range-dependent ocean environments. In this algorithm, we considered depth-dependence of sound speed through rays based on a rectangular cell method and layer method. Range-dependence of sound speed was implemented based on a split-step method in the range direction. Eigen-ray is calculated through an interpolation of ray bundles and Gaussian interpolation function was used. The received time signal of sonar was simulated by Fourier transform of eigen-ray solution in the frequency domain. Finally, for the verification of proposed algorithm, we compared the results of transmission loss with other validated models such as BELLHOP, SNUPE, KRAKEN and OASES, for the Pekeris waveguide, wedge, and deep ocean environments. As a result, we obtained satisfactory agreements among them.
Modeling and Experimental Verification of Echo Characteristics of 3 Dimensional Underwater Target
You, Seung-Ki ; Kim, Sunhyo ; Choi, Jee Woong ; Kang, Donhyug ; Jeong, Dongmin ;
The Journal of the Acoustical Society of Korea, volume 33, issue 3, 2014, Pages 174~183
DOI : 10.7776/ASK.2014.33.3.174
When a active sonar signal is transmitted and returned back from a target, it has been distorted by various properties of acoustic channel such as multipath arrivals. And signals have been appeared to be different form by target position and attitude. Therefore, we simulated the target echo signal using 3 dimensional target model include reflects target features. In this paper, we develop components form of a simulated target model is made up equally spaced highlight points, and each part of the target consists of shape function. We can simulate a target echo signal and Target strength (TS) according to wave incident angle. To verify, we made small scale target in kit form and we had got underwater target signal for comparing simulation result in water tank.
An Effective Crossover Filter Choice of Multi-Way Loudspeaker System
Kang, Seong-Hoon ; Jung, Han-Kyo ;
The Journal of the Acoustical Society of Korea, volume 33, issue 3, 2014, Pages 184~190
DOI : 10.7776/ASK.2014.33.3.184
Although it is ideal that the sound with the range of 20 ~ 20,000 Hz is produced by the loudspeaker system composing of only one loudspeaker unit, it is almost impossible now. Therefore, the audible frequency range is now produced by the loudspeaker system, which is consisted of more than two loudspeaker units. The multi-way loudspeaker system certainly requires a crossover filter, which is divided the audible frequency into low and high frequency ranges. The crossover frequency of filter usually is in the range of 1 ~ 4 kHz, the frequency range can largely affect to the sound articulation and quality. It is an example that the phase and amplitude at the crossover frequency can be different from each other, due to the variously reasons. Conversely, they can not produce the smooth frequency response due to the different distance between the two loudspeaker units and electrical properties. As a result, the sound articulation and quality can be degraded. Therefore, the phase and amplitude response at the crossover frequency has to be deeply considered, in order to exactly match the woofer and tweeter. In this study, it is proposed the methods which are the flat frequency and phase response to be obtained by adjusting of the delay time between loudspeaker units, and the choice of filter to be considered the roll-off properties of each unit. It is achieved the frequency response with
dB, and the sound articulation is also improved.
Propagation of Structural Waves along Waveguides with Non-Uniformities Using Wavenumber Domain Finite Elements
Ryue, Jungsoo ;
The Journal of the Acoustical Society of Korea, volume 33, issue 3, 2014, Pages 191~199
DOI : 10.7776/ASK.2014.33.3.191
Wave reflection and transmission characteristics in waveguides are an important issue in many engineering applications. A combined spectral element and finite element (SE/FE) method is used to investigate the effects of local non-uniformities but limited at relatively low frequencies because the SE is formulated by using a beam theory. For higher frequency applications, a method named a combined spectral super element and finite element (SSE/FE) method was presented recently, replacing spectral elements with spectral super elements. This SSE/FE approach requires a long computing time due to the coupling of SSE and FE matrices. If a local non-uniformity has a uniform cross-section along its short length, the FE part could be further replaced by SSE, which improves performance of the combined SSE/FE method in terms of the modeling effort and computing time. In this paper SSEs are combined to investigate the characteristics of waves propagating along waveguides possessing geometric non-uniformities. Two models are regarded: a rail with a local defect and a periodically ribbed plate. In the case of the rail example, firstly, the results predicted by a combined SSE/FE method are compared with those from the combined SSEs in order to justify that the combined SSEs work properly. Then the SSEs are applied to a ribbed plate which has periodically repeated non-uniformities along its length. For the ribbed plate, the propagation characteristics are investigated in terms of the propagation constant.
Analysis of Ultrasound Synthetic Transmit Focusing Using Plane Waves
Lee, Jong Pil ; Song, Jae Hee ; Song, Tai-Kyong ;
The Journal of the Acoustical Society of Korea, volume 33, issue 3, 2014, Pages 200~209
DOI : 10.7776/ASK.2014.33.3.200
In this paper, we present a general model for synthetic transmit focusing method using plane waves (STF-PW) of which the properties are investigated through mathematical analysis and compared with those of the conventional focusing method. The analysis results show that STF-PW produces non-diffracting beams in the sense that their main lobe widths do not change with depth. We also present a method for synthesis of plane waves to obtain a desired main lobe width while preventing grating lobe generation and a method for broadening the region over which the non-diffracting property is maintained. The proposed model and analysis results were validated through computer simulations.
Audio Fingerprinting Based on Constant Q Transform for TV Commercial Advertisement Identification
Ryu, Sang Hyeon ; Kim, Hyoung-Gook ;
The Journal of the Acoustical Society of Korea, volume 33, issue 3, 2014, Pages 210~215
DOI : 10.7776/ASK.2014.33.3.210
In spite of distortion caused by noise and echo, the audio fingerprinting technique must identify successfully an audio source. This audio fingerprinting technique is applying for TV commercial advertisement identification. In this paper, we propose a robust audio fingerprinting method for TV commercial advertisement identification. In the proposed method, a prominent audio peak pair fingerprint based on constant Q transform improves the accuracy of the audio fingerprinting system in real noisy environments. Experimental results confirm that the proposed method is quite robust than previous audio fingerprinting method in different noise conditions and achieves promising accurate results.
Fast Speaker Identification Using a Universal Background Model Clustering Method
Park, Jumin ; Suh, Youngjoo ; Kim, Hoirin ;
The Journal of the Acoustical Society of Korea, volume 33, issue 3, 2014, Pages 216~224
DOI : 10.7776/ASK.2014.33.3.216
In this paper, we propose a new method to drastically reduce computational complexity in Gaussian Mixture Model (GMM)-based Speaker Identification (SI). Generally, GMM-based SI systems have very high computational complexity proportional to the length of the test utterance, the number of enrolled speakers, and the GMM size. These make the SI systems difficult to be used in various real applications in spite of their broad applicability. Thus, a trade-off between computational complexity and identification accuracy is considered as a primary issue for practical applications. In order to reduce computational complexity sharply with a little loss of accuracy, we introduce a method based on the Universal Background Model (UBM) clustering approach and then we show that it can be used successfully in real-time applications. In experiments with the proposed algorithm, we obtained a speed-up factor of 6 with a negligible loss of accuracy.