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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 34, Issue 6 - Nov 2015
Volume 34, Issue 5 - Sep 2015
Volume 34, Issue 4 - Jul 2015
Volume 34, Issue 3 - May 2015
Volume 34, Issue 2 - Mar 2015
Volume 34, Issue 1 - Jan 2015
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Acoustic Band Structures in Two-dimensional Phononic Crystals with a Square Lattice in Water
Kim, Yoon Mi ; Lee, Kang Il ; Kang, Hwi Suk ; Yoon, Suk Wang ;
The Journal of the Acoustical Society of Korea, volume 34, issue 5, 2015, Pages 335~342
DOI : 10.7776/ASK.2015.34.5.335
Phononic crystals are composite materials consisting of a periodic arrangement of scattering inclusions in a host material. One of the most important properties of phononic crystals is the existence of band gaps, i.e., ranges of frequencies at which acoustic waves cannot propagate through the structure. The present study aims to investigate theoretically and experimentally the acoustic band structures in two-dimensional (2D) phononic crystals consisting of periodic square arrays of stainless steel solid cylinders with a diameter of 1 mm and a lattice constant of 1.5 mm in water. The theoretical dispersion relation that depicts the relationship between the frequency and the wave vector was calculated along the
direction of the first Brillouin zone using the finite element method to predict the band structures in the 2D phononic crystals. The transmission and the reflection coefficients were measured in the 2D phononic crystals with 1, 3, 5, 7, and 9 layers of stainless steel cylinders stacked in the perpendicular direction to propagation at normal incidence. The theoretical dispersion relation exhibited five band gaps at frequencies below 2 MHz, the first gap appearing around a frequency of 0.5 MHz. The location and the width of the band gaps experimentally observed in the transmission and the reflection coefficients appeared to coincide well with those determined from the theoretical dispersion relation.
Asymmetric Directionality of Broadband Ship Radiation Noise at Bow-Stern Aspect
Lee, Keunhwa ; Kim, Minkyu ; Seong, Woojae ;
The Journal of the Acoustical Society of Korea, volume 34, issue 5, 2015, Pages 343~350
DOI : 10.7776/ASK.2015.34.5.343
In this paper, we perform a study on the directionality of broadband ship radiation noise, mainly resulting from propeller cavitation. By examining a few foreign studies for ship radiation noise and domestic data measured in Korean waters, it is reconfirmed that the asymmetric directionality of the ship radiation noise at bow and stern aspect is observed commonly. In order to explore the reason of this asymmetric directionality, a numerical analysis, based on the acoustic boundary element method, is applied into the geometric form equal to the commercial ship used in the domestic experiment. The numerical result demonstrates that the diffraction of the propeller cavitation noise by ship is a primary cause of the bow-stern asymmetry in the directionality of ship radiation noise.
Fabrication and Characterization of an Underwater Acoustic Tonpilz Vector Sensor for the Estimation of Sound Source Direction
Lim, Youngsub ; Roh, Yongrae ;
The Journal of the Acoustical Society of Korea, volume 34, issue 5, 2015, Pages 351~359
DOI : 10.7776/ASK.2015.34.5.351
Typical underwater acoustic transducers detect only the magnitude of an acoustic pressure and they have the limitation of not being able to recognize the direction of the sound signal. Hence, the authors of this paper proposed a new vector sensor structure based on Tonpilz transducers that could detect both the magnitude and the direction of a sound pressure. In the proposed structure, the piezoceramic ring was divided into four segments, and proper combination of the output voltages of the segments in response to the external sound pressure could provide the information on the orientation of the sound source. In this paper, a Tonpilz transducer has been fabricated to have the proposed structure and its characteristics has been measured to confirm the validity of the proposed structure.
Vibration Analysis for Infinite Length Waveguide Structures Connected with Finite Length Structures Using Impedance Coupling
Ryue, Jungsoo ; Lee, Jaehong ; Hong, Chinsuk ; Shin, Ku-Kyun ;
The Journal of the Acoustical Society of Korea, volume 34, issue 5, 2015, Pages 360~370
DOI : 10.7776/ASK.2015.34.5.360
In case that an infinite length waveguide structure is connected with a finite length structure, it is required to combine a wave approach for the waveguide structure and a modal approach for the finite length structure to investigate the dynamic response of the connected target structure. In this study, the wavenumber finite element (WFE) analysis is adopted for the infinite length waveguide substructure and a finite element (FE) method is applied for the finite length substructure and then their results are coupled in terms of the impedance or mobility at the connected points between the substructures. As a structural model, an infinite length cylindrical shell with a rectangular plate inside is regarded. These two substructures are connected at the four corner points of the plate, rigidly or resiliently. From this investigation, it was confirmed that the wave approach (WFE method) and modal approach (FE method) can be combined by the impedance coupling.
Sound Blocking Using Acoustic Metamaterial Scaling
Park, SungJun ; Song, Kyungjun ; Kim, Jedo ;
The Journal of the Acoustical Society of Korea, volume 34, issue 5, 2015, Pages 371~376
DOI : 10.7776/ASK.2015.34.5.371
In this study, we use 1:1, 1:2, and 1:4 scale zig-zag shape acoustic metamaterial structure to achieve broad and effective sound blocking at the subwavelength scale. The SPL(Sound Pressure Level) results show that the SPL loss of the scaled metamaterial slab in series is a superposition of individual SPL losses. Also, we show that the metamaterial tailors the material properties to achieve high impedance and high refractive index using effective medium theory. Our results show that broad and effective sound blocking is possible at the subwavelength scale just by scaling acoustic metamaterial.
Secondary Path Estimation Algorithm Based on Residual Music Canceller for Noise Cancelling Headphone
Ji, Youna ; Lee, Keunsang ; Park, Youngcheol ;
The Journal of the Acoustical Society of Korea, volume 34, issue 5, 2015, Pages 377~384
DOI : 10.7776/ASK.2015.34.5.377
An active noise control (ANC) algorithm for noise canceling headphone is proposed. In this study, the feedback ANC operated with the filtered-x least mean square algorithm (FxLMS) algorithm is used to attenuate the undesired noise. Also an adaptive residual music canceller (RMC) is proposed for enhancing the accuracy of the reference signal of the feedback ANC. Simulation results show that a high quality of music sound can be consistently achieved in a time-varying secondary path situation.
Analyses of the Railway Noise Transmission Characteristics of the Rooms in High-speed Train Stations Depending on Building Types
Park, Chan-Jae ; Haan, Chan-Hoon ;
The Journal of the Acoustical Society of Korea, volume 34, issue 5, 2015, Pages 385~393
DOI : 10.7776/ASK.2015.34.5.385
The speed of train has rapidly been increased in accordance with the developed railway technology. Nowadays, high-speed trains were introduced which has the speed faster than 400 km/h. In Korea, a lots of efforts were undertaken to increase the speed of train faster than 350 km/h, however noise and vibration are still the main problems to solve for realization of the high-speed train. In the case of operation speed faster than 350 km/h, it can be easily presumed that the noise and vibration damages could be increased in the train stations which are close to the passing railway tracks. Thus, the noise in the five different types of high-speed train stations were analyzed including stations built on the ground, underground, under rail, and two types on rail. The present paper predicts noises inside the stations depending on the speed of the passing trains and analyze the noise comparing with noise criteria (NC). Sound insulation performance of each part of buildings was calculated using the transmission noise formula and computer modeling, Finally, a series of processes were introduced to satisfy the aural environment with the optimum interior noise criteria by changing interior finishing materials.
A Constant Modulus Algorithm (CMA) for Blind Acoustic Communication Channel Equalization with Improved Convergence Using Switching between Projected CMA and Algebraic Step Size CMA
Lim, Jun-Seok ; Pyeon, Yong-Guk ;
The Journal of the Acoustical Society of Korea, volume 34, issue 5, 2015, Pages 394~402
DOI : 10.7776/ASK.2015.34.5.394
CMA (Constant Modulus Algorithm) is one of the well-known algorithms in blind acoustic channel equalization. Generally, CMA converges slowly and the speed of convergence is dependent on a step-size in the CMA procedure. Many researches have tried to speed up the convergence speed by applying a variable step-size to CMA, e.g. the orthogonal projection CMA and algebraic optimal step-size CMA. In this paper, we summarize these two algorithms, and we propose a new CMA with improved convergence performance. The improvement comes from the switching between the orthogonal projection CMA and algebraic optimal step-size CMA. In simulation results, we show the performance improvement in the time invariant channels as well as in time varying channel.
Performance Improvement of Packet Loss Concealment Algorithm in G.711 Using Adaptive Signal Scale Estimation
Kim, Tae-Ha ; Lee, In-Sung ;
The Journal of the Acoustical Society of Korea, volume 34, issue 5, 2015, Pages 403~409
DOI : 10.7776/ASK.2015.34.5.403
In this paper, we propose Packet Loss Concealment (PLC) method using adaptive signal scale estimation for performance improvement of G.711 PLC. The conventional method controls a gain using 20 % attenuation factor when continuous loss occurs. However, this method lead to deterioration because that don't consider the change of signal. So, we propose gain control by adaptive signal scale estimation through before and after frame information using Least Mean Square (LMS) predictor. Performance evaluation of proposed algorithm is presented through Perceptual Evaluation of Speech Quality (PESQ) evaulation.