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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
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Volume & Issues
Volume 29, Issue 8 - Nov 2010
Volume 29, Issue 7 - Oct 2010
Volume 29, Issue 6 - Aug 2010
Volume 29, Issue 5 - Jul 2010
Volume 29, Issue 4 - May 2010
Volume 29, Issue 3 - Apr 2010
Volume 29, Issue 2 - Feb 2010
Volume 29, Issue 1 - Jan 2010
Selecting the target year
Optimization of Array Configuration in Time Reversal Processing
Joo, Jae-Hoon ; Kim, Jea-Soo ; Ji, Yoon-Hee ; Chung, Jae-Hak ; Kim, Duk-Yung ;
The Journal of the Acoustical Society of Korea, volume 29, issue 7, 2010, Pages 411~421
A time-reversal mirror (TRM) is useful in diverse areas, such as reverberation ing, target echo enhancement and underwater communication. In underwater communication, the bit error rate has been improved significantly due to the increased signal-to-noise ratio by spatio-temporal focusing. This paper deals with two issues. First, the optimal number of array elements for a given environment was investigated based on the exploitation of spatial diversity. Second, an algorithm was developed to determine the optimal location of the given number of array elements. The formulation is based on a genetic algorithm maximizing the contrast between the foci and area of interest as an objective function. In addition, the developed algorithm was applied to the matched field processing with ocean experimental data for verification. The sea-going data and simulation showed almost 3 dB improvement in the output power at the foci when the array elements were optimally distributed.
Analysis of the Radiation Pattern in Relation to the Head Mass Shape Applicable to a Tonpilz Transducer
Kim, Hoe-Yong ; Roh, Yong-Rae ;
The Journal of the Acoustical Society of Korea, volume 29, issue 7, 2010, Pages 422~430
The radiation property of a Tonpilz transducer is influenced by the structural variables of the transducer. In this study, with respect to a single mode Tonpilz transducer, the radiation patterns were calculated for different head mass geometries of the same effective radiation area. The shapes of the head mass analyzed were the most popular circular, regular triangular, square, regular hexagonal and regular octagonal types, and radiation pattern equations were derived for each of the head mass shapes. Based on the derived equations, radiation patterns in accordance with the shape and size of the head mass were calculated and the results were compared with each other. Validity of the calculation results were confirmed by means of finite element analysis.
Analysis of the Radiation Pattern of Conformal Array Transducers
Kim, Hoe-Yong ; Roh, Yong-Rae ;
The Journal of the Acoustical Society of Korea, volume 29, issue 7, 2010, Pages 431~438
The radiation pattern of conformal transducers installed on a curved surface is likely to be complicated depending on the array pattern on the curved surface. In this research, the acoustic sources constituting a conformal transducer are arrayed in equi-angle, equi-interval, and geodesic dome forms, and the radiation pattern function of each of the array geometries has been derived, and therewith the radiation pattern has been analyzed for each array geometry. Based on the analysis result, we have determined the equi-interval array geometry that provides the widest beam width with the lowest side lobe level among the three array geometries. Results of the present work are expected to be utilized to the design of conformal transducer structures.
A Study on the Resonant Characteristics of a Tonpilz Transducer with a Fixed Tail Mass
Kim, Jin-Wook ; Kim, Won-Ho ; Joh, Chee-Young ; Roh, Yong-Rae ;
The Journal of the Acoustical Society of Korea, volume 29, issue 7, 2010, Pages 439~447
In this paper, the resonant characteristic of a Tonpilz transducer with a fixed tail mass has been researched and the feasibility to utilize the transducer in that resonant frequency has been analyzed. The additional resonance is occurred by adhering an elastic tube to the tail mass of a conventional Tonpilz transducer and fixing the other end of the tube. The characteristic of this low resonant mode is analyzed by means of the finite element method, then it is shown that this mode is affected by the variation of the stiffness of the tube as well as the mass of the head mass and tail mass. Based on the analysis results, the Tonpilz transducer is designed to meet specific performance conditions.
A Numerical Method for Analysis of the Sound and Vibration of Waveguides Coupled with External Fluid
Ryue, Jung-Soo ;
The Journal of the Acoustical Society of Korea, volume 29, issue 7, 2010, Pages 448~457
Vibrations and wave propagations in waveguide structures can be analysed efficiently by using waveguide finite element (WFE) method. The WFE method only models the 2-dimensional cross-section of the waveguide with finite elements so that the size of the model and computing time are much less than those of the 3-dimensional FE models. For cylindrical shells or pipes which have simple cross-sections, the external coupling with fluids can be treated theoretically. For waveguides of complex cross-sectional geometries, however, numerical methods are required to deal with external fluids. In this numerical approach, the external fluid is modelled by the boundary elements (BEs) and connected to WFEs. In order to validate this WFE/BE method, a pipe submerged in water is considered in this study. The dispersion diagrams and point mobilities of the pipe simulated are compared to those that theoretically obtained. Also the acoustic powers radiated from the pipe are predicted and compared in both cases of air and water as an external medium.
Development of a Listener Position Adaptive Real-Time Sound Reproduction System
Lee, Ki-Seung ; Lee, Seok-Pil ;
The Journal of the Acoustical Society of Korea, volume 29, issue 7, 2010, Pages 458~467
In this paper, a new audio reproduction system was developed in which the cross-talk signals would be reasonably cancelled at an arbitrary listener position. To adaptively remove the cross-talk signals according to the listener's position, a method of tracking the listener position was employed. This was achieved using the two microphones, where the listener direction was estimated using the time-delay between the two signals from the two microphones, respectively. Moreover, room reverberation effects were taken into consideration where linear prediction analysis was involved. To remove the cross-talk signals at the left-and right-ears, the paths between the sources and the ears were represented using the KEMAR head-related transfer functions (HRTFs) which were measured from the artificial dummy head. To evaluate the usefulness of the proposed listener tracking system, the performance of cross-talk cancellation was evaluated at the estimated listener positions. The performance was evaluated in terms of the channel separation ration (CSR), a -10 dB of CSR was experimentally achieved although the listener positions were more or less deviated. A real-time system was implemented using a floating-point digital signal processor (DSP). It was confirmed that the average errors of the listener direction was 5 degree and the subjects indicated that 80 % of the stimuli was perceived as the correct directions.
Method for Spectral Enhancement by Binary Mask for Speech Recognition Enhancement Under Noise Environment
Choi, Gab-Keun ; Kim, Soon-Hyob ;
The Journal of the Acoustical Society of Korea, volume 29, issue 7, 2010, Pages 468~474
The major factor that disturbs practical use of speech recognition is distortion by the ambient and channel noises. Generally, the ambient noise drops the performance and restricts places to use. DSR (Distributed Speech Recognition) based speech recognition also has this problem. Various noise cancelling algorithms are applied to solve this problem, but loss of spectrum and remaining noise by incorrect noise estimation at low SNR environments cause drop of recognition rate. This paper proposes methods for speech enhancement. This method uses MMSE-STSA for noise cancelling and ideal binary mask to compensate damaged spectrum. According to experiments at noisy environment (SNR 15 dB ~ 0 dB), the proposed methods showed better spectral results and recognition performance.