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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 27, Issue 8 - Nov 2008
Volume 27, Issue 7 - Oct 2008
Volume 27, Issue 6 - Aug 2008
Volume 27, Issue 5 - Jul 2008
Volume 27, Issue 4 - May 2008
Volume 27, Issue 3 - Apr 2008
Volume 27, Issue 2 - Feb 2008
Volume 27, Issue 1 - Jan 2008
Selecting the target year
Optimal Design and Analysis of a Medical Imaging Ultrasonic Array Sensor
Kim, Hoe-Yong ; Roh, Yong-Rae ;
The Journal of the Acoustical Society of Korea, volume 27, issue 6, 2008, Pages 263~270
The performance of an ultrasonic array sensor is determined by the properties of constituent materials and the effects of many structural parameters. In this study, with the finite element method, variation of the performances of an ultrasonic array sensor was analyzed in relation to its structural variables. Based on the analysis result, the structure of the ultrasonic array sensor was optimized to provide the highest sensitivity while satisfying such requirements as fractional bandwidth, center frequency and -20 dB pulse length. The optimization was carried out with the SQP-PD method for a target function composed of the ultrasonic array sensor performance. The optimized ultrasonic array sensor satisfied all the required specifications to be applicable to medical imaging diagnosis. The design technology in this paper can be utilized for other ultrasonic array sensors of a similar structure.
Characteristics Variation Analysis by Shape of Piezoelectric Ultrasonic Transducer with Non-Uniform Thickness
Kim, Dong-Hyun ; Kim, Jung-Soon ; Kim, Moo-Joon ; Ha, Kang-Lyeol ;
The Journal of the Acoustical Society of Korea, volume 27, issue 6, 2008, Pages 271~278
The electro-mechanical characteristics were theoretically analyzed for the wideband ultrasonic transducer made of non-uniform thickness piezoelectric vibrator. This paper proposes a combination of exponential functions which describes the thickness variation along the length of the vibrator to derive the input admittance and power transfer function of the transducer. The bandwidth and the power transfer function of the transducer were investigated while the lateral shape of the vibrator changes. The results showed there is an optimum shape for the wideband characteristics of the transducer, and the bandwidth has increased up to over 100% as the ratio of minimum value of thickness to maximum value decreases. However, the power transfer function had a downward trend as the ratio of thickness decreases. Also we confirmed that even though the value of transfer function increases as the length of the piezoelectric vibrator increases, the shape providing wideband characteristics is very limited. It means that precision processing is required to manufacturing a wideband ultrasonic transducer with high efficiency.
Evaluation of Multiple Access Protocols for Controlling UUV
Jung, Seung-Back ; Cho, Jin-Soo ; Shim, Tae-Bo ;
The Journal of the Acoustical Society of Korea, volume 27, issue 6, 2008, Pages 279~285
This study includes the efficiency assessment of a multiple access protocol for UUV (Underwater unmanned vehicle) control. Most of UUVs are controled by wire now; however, wireless control is demanded because of the demerit of the wire control that limits the place and activity. This study simulates efficiency of a standardization multiple access protocol (Pure ALOHA, Slotted ALOHA, Nonpersistent CSMA, Slotted Nonpersistent ISMA) formed for the purpose of performing wireless communication controlled by the ship or communication buoy at the sea surface and by the under water communication node at the bottom in order to efficiently control the UUV's. Results show that no significant changes occur related to changing type of the mother ship and the communication node; In addition, the Non-persistent CSMA and the Slotted Non-persistent ISMA show relatively high efficiency for underwater acoustic communication.
The Analysis about Channel Code Performance of Underwater Channel
Bae, Jong-Tae ; Kim, Min-Hyuk ; Choi, Suk-Soon ; Jung, Ji-Won ; Chun, Seung-Yong ; Dho, Kyeong-Cheol ;
The Journal of the Acoustical Society of Korea, volume 27, issue 6, 2008, Pages 286~295
Underwater acoustic communication has multi path error because of reflection by sea-level and sea-bottom. The multipath of underwater channel causes signal distortion and error floor. In this paper, we consider the use of various channel coding schemes such as RS code, convolutional code, cross-layer code and LDPC code in order to compensate the multipath effect in underwater channel. As shown in simulation results, characteristic of multipath error is similar to that of random error, so interleaver has little effect for error correcting. For correcting of error floor by multipath error, it is necessary strong channel codes like LDPC code that is similar to Shannon's limit. And the performance of concatenated codes including RS codes has better performance than using singular channel codes.
Connection between Acoustical Parameters and Solo Performance on a Concert Hall Stage
Kim, Yong-Hee ; Lee, Chang-Woo ; Seo, Chun-Ki ; Jeon, Jin-Yong ;
The Journal of the Acoustical Society of Korea, volume 27, issue 6, 2008, Pages 296~302
This study investigated that the preference model of soloist performers for both vocal and instrumental types in terms of a stage support parameter, ST1. The test was carried out on a stage of a fan-shaped multi-purpose hall with orchestra shell. Objective measurements were carried out at 15 positions on the stage to evaluate various stage condition. The results showed that ST1 varies between -19.9 and -11.3 dB. Vocal and instrumental players participated in performance evaluation test as they played at 5 selected positions according to ST1 values. Players' preference was evaluated by 5-point rating and rank ordering method. As a result, it was found that the preference model of vocalist is different from that of instrumentalist. It was also found that the ST1 does not correlate well with the performer's preference.
The Effect of Word Frequency on Noun Definitions
Lee, Chan-Jong ;
The Journal of the Acoustical Society of Korea, volume 27, issue 6, 2008, Pages 303~308
The purpose of the present study is to investigate that word frequency has significant influence on noun definitions in Korean. The experimental group was 80 students from Elementary school, Middle school, High school and University. They rated familiarity and wrote definitions for nouns. Noun definitions were analyzed with semantic categories such as "use/purpose," "description," "association/relation," "partial explanation," "explanation," "error," "partial explanation-attribute," "partial explanation-specific class," "partial explanation-nonspecific class," "explanation-specific class," "explanation-nonspecific class." As a result, they showed familiarity for high-frequency nouns. "EXPL" categories that use class terms or critical attributes were used more frequently in definitions of high-frequency nouns compared with low-frequency nouns. They increased with age and errors decreased with age. Word frequency had a significant influence on noun definitions.
A Study of BWE-Prediction-Based Split-Band Coding Scheme
Song, Geun-Bae ; Kim, Austin ;
The Journal of the Acoustical Society of Korea, volume 27, issue 6, 2008, Pages 309~318
In this paper, we discuss a method for efficiently coding the high-band signal in the split-band coding approach where an input signal is divided into two bands and then each band may be encoded separately. Generally, and especially through the research on the artificial bandwidth extension (BWE), it is well known that there is a correlation between the two bands to some degree. Therefore, some coding gain could be achieved by utilizing the correlation. In the BWE-prediction-based coding approach, using a simple linear BWE function may not yield optimal results because the correlation has a non-linear characteristic. In this paper, we investigate the new coding scheme more in details. A few representative BWE functions including linear and non-linear ones are investigated and compared to find a suitable one for the coding purpose. In addition, it is also discussed whether there are some additional gains in combining the BWE coder with the predictive vector quantizer which exploits the temporal correlation.
Enhancement of Speech/Music Classification for 3GPP2 SMV Codec Employing Discriminative Weight Training
Kang, Sang-Ick ; Chang, Joon-Hyuk ; Lee, Seong-Ro ;
The Journal of the Acoustical Society of Korea, volume 27, issue 6, 2008, Pages 319~324
In this paper, we propose a novel approach to improve the performance of speech/music classification for the selectable mode vocoder (SMV) of 3GPP2 using the discriminative weight training which is based on the minimum classification error (MCE) algorithm. We first present an effective analysis of the features and the classification method adopted in the conventional SMV. And then proposed the speech/music decision rule is expressed as the geometric mean of optimally weighted features which are selected from the SMV. The performance of the proposed algorithm is evaluated under various conditions and yields better results compared with the conventional scheme of the SMV.