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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 32, Issue 6 - Nov 2013
Volume 32, Issue 5 - Sep 2013
Volume 32, Issue 4 - Jul 2013
Volume 32, Issue 3 - May 2013
Volume 32, Issue 2 - Mar 2013
Volume 32, Issue 1 - Jan 2013
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Parametric Array Signal Generating System using Transducer Array
Lee, Jaeil ; Lee, Chong Hyun ; Bae, Jinho ; Paeng, Dong-Guk ; Choe, Mi Heung ; Kim, Won-Ho ;
The Journal of the Acoustical Society of Korea, volume 32, issue 4, 2013, Pages 287~293
DOI : 10.7776/ASK.2013.32.4.287
We present a parametric array signal generating system using
transducer array which is composed of multi-resonant frequency transducers of 20kHz and 32.5kHz. To drive transducer array, sixteen channel amplifier using LM1875 chips is designed and implemented, and the PXI system based on the LabView 8.6 for arbitrary signal generation and analysis is used. Using the proposed system, we measure sound pressure level and beam pattern of difference frequency and verify the nonlinear effect of difference frequency. The theoretical absorption range and the Rayleigh distance are 15.51m and 1.933m, respectively and we verify that sound pressure of difference frequency is accumulated and increased at the near-field shorter than the Rayleigh distance. We verify that the beam pattern of the measured difference frequency and the beam pattern obtained by the superposition of two primary frequencies are similar, and high directional parametric signal was generated.
Performance of Parametric Array Communication System in Underwater AWGN Channel
Lee, Jaeil ; Lee, Chong Hyun ; Bae, Jinho ; Paeng, Dong-Guk ; Kim, Won-Ho ;
The Journal of the Acoustical Society of Korea, volume 32, issue 4, 2013, Pages 294~300
DOI : 10.7776/ASK.2013.32.4.294
In this paper, we present performance analysis results of parametric array communication system in terms of theoretical BER and channel capacity of MIMO in underwater AWGN channel by using simplified SNR of difference frequency. The SNR of the difference frequency is calculated by using transmission loss, noise level, and source level of difference frequency in which nonlinear effect is considered. By assuming primary frequencies as 210 kHz and 190 kHz, difference frequency as 20 kHz, transducer diameter as 0.1 m, and noise level as 50 dB and the requested BER as
, we obtain parametric array communication range gains over the communication system using primary frequency of 59.11 km in fresh water and 5 km in sea water, respectively. Also we obtain range gains of 38.84 km and 46.38 km in fresh water, and 3.88 km and 4.38 km in sea water when we use SISO and
MIMO parametric array communications for the channel capacity of 10 bps/Hz.
An Acoustic Reception Ability Analysis of SONAR Multilayer Structures by Using Elastic Theory
Kwon, Hyun-Wung ; Hong, Suk-Yoon ; Song, Jee-Hun ; Kim, Sung-Hee ; Jeon, Jae-Jin ; Seo, Young-Soo ;
The Journal of the Acoustical Society of Korea, volume 32, issue 4, 2013, Pages 301~307
DOI : 10.7776/ASK.2013.32.4.301
SONAR detection performance is one of the key survivability factors in underwater weapon systems. In order to catch the acoustic ability of SONAR, multilayer SONAR structures are analyzed using the elastic theory. The applied results for the simple models are compared with those from commercial program, ANSYS, and the reliable results are obtained. The analysis of sound pressure level (SPL) and echo reduction (ER) by the thickness change of multilayer SONAR structures are performed using the verified elastic theory. As the thickness of anechoic layer is increased, SPL is distributed evenly and ER is increased slightly with the frequency. In decoupling layers and steel layers, SPL are hardly changed and ER is slightly decreased with the thickness increase of those layers. SPL and ER are not affected by the thickness change of the carbon reinforced plastic (CRP) layer. Therefore, to improve the acoustic ability of multilayer SONAR structures, the thickness increase of the anechoic layer and minimization of the decoupling layer, steel layer and CRP layer are desirable.
Time-domain Geoacoustic Inversion of Short-range Acoustic Data with Fluctuating Arrivals
Park, Cheolsoo ; Seong, Woojae ; Gerstoft, Peter ; Hodgkiss, William S. ;
The Journal of the Acoustical Society of Korea, volume 32, issue 4, 2013, Pages 308~316
DOI : 10.7776/ASK.2013.32.4.308
A set of experiments (Shallow Water 2006, SW06) was carried out in shallow water near the New Jersey shelf break in summer 2006. Significant fluctuations in direct and surface reflected arrivals were observed from the chirp data (1100~2900 Hz) measured on a vertical line array. This paper presents a geoacoustic inverssion technique for short-range acoustic data with fluctuating arrivals and inversion results of experimental data. In order to reduce effects of random sea surface on the inversion, the acoustic energy back-propagated from the array to the source through direct and bottom-reflected paths is defined as the objective function. A multi-step inversion scheme is applied to the data using VFSR (Very Fast Simulated Reannealing) optimization technique. The inversion results show a source depth oscillation period equal to the measured ocean surface wave period. The inverted bottom sound speed is 1645 m/s and is similar to that estimated by other work at the same site.
Study on Design Optimization of a Planar Multi-layer Structure for Noise Reduction of Underwater Acoustic Sensors
Kim, G.C. ; Kim, S.H. ; Kim, J.K. ; Kil, H.G. ; Hong, S.Y. ; Song, J.H. ; Gwon, H.W. ; Seo, Y.S. ; Jeon, J.J. ;
The Journal of the Acoustical Society of Korea, volume 32, issue 4, 2013, Pages 317~328
DOI : 10.7776/ASK.2013.32.4.317
In this paper, the optimization has been performed to design a multi-layer structure that is used as a structure for noise reduction of acoustic sonar sensors in underwater vehicles. Two design goals are considered to reduce self-noise from own machineries and to enhance acoustic signals detected from outside. Both distinct and continuous design parameters have been used such as selection of material properties of each layer and thickness of each layer, respectively. The sensitivity of design parameters has been analyzed and the evolutionary algorithm has been implemented for design optimization. For design optimization process, each of the design goals and the two combined design goals have been considered to analyze the achievement of those design goals.
Sound Quality Improvement of Car Interior Noise Through the Change of Order Spectrum
Shin, Sung-Hwan ; Hashimoto, Takeo ;
The Journal of the Acoustical Society of Korea, volume 32, issue 4, 2013, Pages 329~334
DOI : 10.7776/ASK.2013.32.4.329
Order spectrum analysis is widely used to grasp the features of noises due to powertrain system including engine and intake/exhaust system. It is known from many previous researches that order components related to the first and second firing frequencies of engine considerably affect the noise of car interior. The purpose of this paper is to find out the difference in sound quality: Pleasantness of car interior noise according to the change of its order spectrum. For this, car interior noises of 6-cylinder and 4-cylinder engines are recorded and their order spectrum levels are modified by applying adaptive digital filters. After subjective listening test employing paired comparison method is conducted, it is investigated that the level change of half-order components is a noticeable factor to improve Pleasantness of the car interior noises whereas level decrease of firing order does not always give the positive effect on its sound quality.
Effect of the Inter-aural Level Differences on the Speech Intelligibility Depending on the Room Absorption in Classrooms
Park, Chan-Jae ; Haan, Chan-Hoon ;
The Journal of the Acoustical Society of Korea, volume 32, issue 4, 2013, Pages 335~345
DOI : 10.7776/ASK.2013.32.4.335
The present study investigates the effect of the inter-aural level difference(ILD) on the syllable articulation test in classrooms which can be occurred by the absorption of interior surfaces. In order to do this, the sound absorbing materials were installed in the classroom and sound pressure level(SPL) at each ear was measured using binaural recording systems. Also, syllable articulation tests were carried out at a classroom with and without sound absorption materials by 20 students who have normal hearing condition, in order to investigates the effect of the ILD on the speech intelligibility. As a result, it was found that the larger inter-aural level differences was occurred at the nearer positions to lateral walls after sound absorptions were applied to lateral walls in the classroom. At some places, the measured ILD was lager than JND of sound level (3dB). Also, it was shown that the correlation coefficient of inter-aural level difference with the score of syllable test has the significant result(-0.441). Thus, It is concluded that ILD can affect the subjective speech intelligibility in classrooms.
Implementation of the High-Quality Audio System with the Separately Processed Musical Instrument Channels
Kim, Tae-Hoon ; Lee, Sang-Hak ; Kim, Dae-Kyung ; Lee, Sang-Chan ;
The Journal of the Acoustical Society of Korea, volume 32, issue 4, 2013, Pages 346~353
DOI : 10.7776/ASK.2013.32.4.346
This paper deals with the implementation of a high-quality audio system for karaoke. For improving the key/tempo changes performance, we separated the audio into many musical instrument channels. By separating musical instrument channels, high-quality key/tempo changes can be achieved and we confirmed this using the cross-correlation distribution and the MOS evaluation. The improved audio system was implemented using the TMS320C6747 DSP with fixed/floating-point operations. The implemented audio system can perform the multi-channel WMA decoding, the MP3 encoding/decoding, the wav playing, the EQ, and the key/tempo changes in real time. The WMA channels used for processing the separated instrument channels. The audio system includs the MP3 encoding/decoding function for playing and recording and the wav channel for the effect sound.
Hough Transform Clutter Reduction Algorithm for Piecewise Linear Path Active Sonar Target Detection and Tracking Improvement
Kim, Seong-Weon ;
The Journal of the Acoustical Society of Korea, volume 32, issue 4, 2013, Pages 354~360
DOI : 10.7776/ASK.2013.32.4.354
In this paper, it is discussed that the detection and tracking performance of the piecewise linear path underwater target is improved using clutter reduction algorithm in heavy clutter density environment. Through clutter reduction algorithm using Hough Transform, measurements which represent clutter features are removed and the performance of target tracking on the remaining measurements is demonstrated applying CMKF-L(Converted Measurement Kalman Filter with Linearization) as tracking filter. Algorithm performance test is conducted using simulation data and real sea-trial data and by applying the proposed algorithm in heavy clutter density environment, it is confirmed that the target is tracked consistently and stably with clutter rejected measurements.
Transmission Line Based Plucked String Model
Lee, Jingeol ; French, Mark ;
The Journal of the Acoustical Society of Korea, volume 32, issue 4, 2013, Pages 361~368
DOI : 10.7776/ASK.2013.32.4.361
As one way to describe the behavior of a vibrating string, analogies to a transmission line have been made based on the fact that they have oppositely travelling waves on each of them. In such analogies, a rigid end to the string has been represented as an open circuit, and the displacement of the string as the current on the transmission line. However it turns out that the rigid end corresponds to a short circuit, the displacement to the voltage by the theory of the transmission line, and it is confirmed by experiments with circuit simulations. Based on these discoveries, a transmission line based plucked string model comprising a transmission line, two piecewise linear current sources, and switches is proposed. The proposed model is validated by showing that the voltage at the arbitrarily chosen location, and the voltage calculated over an infinitesimal portion at the end of the transmission line are consistent with the displacement at the corresponding location and the force on the rigid end of the string from the well known difference form of a wave equation governing the behavior of the string with its fundamental frequency tuned to that for the proposed model, respectively. Moreover, the applicability of the proposed model to modeling string and wind instruments is presented.