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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 24, Issue 8 - Nov 2005
Volume 24, Issue 7 - Oct 2005
Volume 24, Issue 6 - Aug 2005
Volume 24, Issue 5 - Jul 2005
Volume 24, Issue 4 - May 2005
Volume 24, Issue 3 - Apr 2005
Volume 24, Issue 2 - Feb 2005
Volume 24, Issue 1 - Jan 2005
Selecting the target year
Construction of Ultrasonic Power Measurement System and Its Performance Evaluation
Jho Moon Jae ; Kim Yong Tae ; Yun Yong Hyeon ; Jung Suug Soo ;
The Journal of the Acoustical Society of Korea, volume 24, issue 8, 2005, Pages 431~440
The precise measurement of ultrasonic power is important to the qualify assurance and the safety of medical ultrasonic equipments In the Present work, a brier theory was introduced to determine the ultrasonic Power from the time valving balance-indication due to the radiation force acting on an absorbing target and/or other causes such as buoyancy during the repetition of on/off behavior of ultrasonic irradiation. The developed automated system measuring the ultrasonic power was described in detail with the precise mechanical alignment tool , the electric signal generation network, the control and measurement network and the appropriate procedure. The ultrasonic power measured by the developed system was compared to the reference data calibrated by the other national metrology institute at 1 MHz, 5 MHz, 10 MHz, and 15 MHz over the range 10 mW to 10 W. Their relative differences are within
High Frequency Scattering from Cylindrical Scatterer
Kim Kitaek ; Yoon Kwan-Seob ; La Hyoungsul ; Na Jungyul ;
The Journal of the Acoustical Society of Korea, volume 24, issue 8, 2005, Pages 441~446
This paper presents the changes of acoustic scattering pattern from a single cylinder and two identical cylinders in both theoretical calculations and experimental measurements. Bi-static scattering pattern by single cylinder and two parallel cylinders (length 2m, radius 30mm) was measured in
water tank using high frequency projector (120 kHz) and hydrophone. The results show similar agreement between experiment and theory. In case of single cylinder scattering. omni-directional pattern was observed in backward but there are fluctuations or target strength in forward. Interference between each cylinder's scattering fields produce fluctuations of target strength in all directions of two cylinders.
Characteristics of Backscattering of Harmful Algae Using Underwater Ultrasound
Kim Eunhye ; Bok Tae-hoon ; Na Jungyul ; Paeng Dong-Guk ;
The Journal of the Acoustical Society of Korea, volume 24, issue 8, 2005, Pages 447~453
Laboratory measurements were performed in a uni-algae medium Cochlodinium polykrikoides (Phytoplankton, dinoflagellates) using an Underwater Ultrasound
to study Characteristics of Acoustic Backscattering of Harmful algae. In an effort to detect the harmful algal scatterers with population density of less than 300 cells/ml that corresponds to the precaution stage of red tide, backscattered signals from various scatterer-density samples were obtained and analyzed. Correlations between volume backscattering strength (Sv) and population density (cells/ml) of scatterers in the medium have been investigated. Comparison of Volume Backscattering Strengths calculated with the fluid-sphere model  and the measured values showed an agreement.
Bit Error Parameters on Passive Phase Conjugation Underwater Acoustic Communication
Yoon, Jong-Rak ; Park, Moon-Kab ; Ro, Yong-Ju ;
The Journal of the Acoustical Society of Korea, volume 24, issue 8, 2005, Pages 454~461
Time spread due to the multipath in underwater acoustic channel, induces ISI (Inter-Symbol Interference) which degrades the performance of the underwater acoustic communication system. The passive phase conjugation (PPC) which improves the signal to multipath interference ratio (SMR) and therefore reduces the frequency selectivity. is a diversity communication technique giving a less ISI under multipath fading channel. Its frequency selectivity depends on the number of receiver array sensors and time varying source to receiver range. In this study, frequency selectivity of the PPC and its effects on bit error of underwater acoustic communication is analyzed by numerical simulation.
Frame Synchronization Scheme for High Oversampling Rate Based QPSK Receiver in the Underwater Acoustic Burst Transmission
Park Jong-Won ; Kim Seung-Geun ; Lim Young-Kon ; Kim Youngkil ;
The Journal of the Acoustical Society of Korea, volume 24, issue 8, 2005, Pages 462~468
In this paper, we present a frame synchronization scheme for high oversampling rate based QPSK receiver system in the underwater acoustic burst transmission. The proposed frame synchronization scheme determines the frame synchronization by comparing a threshold value with the correlation between the received symbol sequence and rotated 16-symbol length CAZAC sequence, which is made by dividing into two 8-symbol length sequences and then concatenating the latter sequence and the former one. If the correlation value is bigger than the threshold value, the frame detector determines that the frame synchronization is achieved at that sample. Also, the approximated performance of designed frame detector is derived and it is well fit the simulated result.
Investigation of the Acoustic Performance of Music Halls Using Measured Radiation Characteristics of the Korean Traditional Musical Instruments
Haan Chan-Hoon ; Lee Wangu ; Jeong Cheol-Ho ;
The Journal of the Acoustical Society of Korea, volume 24, issue 8, 2005, Pages 469~480
There have been always some difficulties in target setting and conditioning of acoustic performances or the Korean traditional music hall due mainly to the lack of the information on the sound radiation characteristics of Korean musical sources. As the 2nd experiment succeeding the previous study, the radiation characteristics of eight typical Korean traditional musical sources were investigated if precision. The selected musical sources were Geomungo, Haegeum (string), Piri, Taepyeongso (woodwind), Buk, Kwaengguari, Jing (drum), and male Pansori Chang (vocal Performance). The results show that the directivity pattern of each instrument is different and has their own directivity characteristics. Measured directional and spectral characteristics of traditional Korean music sources were implemented into the computation of architectural acoustic measures. Significant differences in the acoustic measures at receiver positions were observed between the results in using the omni-directional source and the directional one. In order to investigate the acoustical characteristics of the instruments depending on the spatial variation four different shapes of halls were introduced including rectangular, fan. horse-shoe and geometrical shapes. Room acoustical parameters such as RT, SPL, C80, LF, STI were calculated at each type or hall. As the results, It was found that the rectangular hall has the most high clarity. lateral energy and STI values among low shapes of halls. It is thought that the suggested source data and design method can be used as a basic reference in the future acoustic design of performance halls for the Korean traditional music.
The Evaluation Structure of Auditory Images on the Streetscapes - The Semantic Issues of Soundscape based on the Students' Fieldwork -
Han Myung-Ho ;
The Journal of the Acoustical Society of Korea, volume 24, issue 8, 2005, Pages 481~491
The purpose of this study is to interpret the evaluation structure of auditory images about streetscapes in urban area on the basis of the semantic view of soundscapes. Using the caption evaluation method. which is a new method, from 2001 to 2005, a total of 45 college students participated in a fieldwork to find out the images of sounds while walking on the main streets of Namwon city. It was able get various data which include elements, features, impressions, and preferences about auditory scene. In Namwon city, the elements of the formation of auditory images are classified into natural sound and artificial sound which include machinery sounds, community sounds. and signal sounds. Also, the features of the auditory scene are classified by kind of sound, behavior, condition, character, relationship of circumference and image. Finally, the impression of auditory scene is classified into three categories, which are the emotions of humans, atmosphere of the streets, and the characteristics of the sound itself. From the relationship between auditory scene and estimation, the elements, features and impressions of auditory scene consist of the items which are positive, neutral, and negative images. Also, it was able to grasp the characteristics of auditory image of place or space through the evaluation model of streetscapes in Namwon city.
Robust Audio Watermarking Using Frequency Coefficient Analysis for MP3 Compression Attack
Jeong Won-Kyo ; Lee Kyeong-Hwan ; Woo Hong-Chae ; Lee Yong-Doo ;
The Journal of the Acoustical Society of Korea, volume 24, issue 8, 2005, Pages 492~497
In this paper, we suggest that the new volume of robust audio watermarking method protects form the MP3 compression attack, mostly used in audio field. Watermarks were inserted at the coefficients repeatedly from low frequencies to high frequencies after DCT transform in commonly used Cox's spread spectrum method. However, our method could be investigated losing frequency when MP3 attacks and make order by small amount of losing frequency and then insert watermarks rightly through statistical analysis. In the result about various sound clips, the suggested method have better performances than Cox's method by preserving watermarks and reducing distortions of the original sounds.
Development of a Korean Speech Recognition Platform (ECHOS)
Kwon Oh-Wook ; Kwon Sukbong ; Jang Gyucheol ; Yun Sungrack ; Kim Yong-Rae ; Jang Kwang-Dong ; Kim Hoi-Rin ; Yoo Changdong ; Kim Bong-Wan ; Lee Yong-Ju ;
The Journal of the Acoustical Society of Korea, volume 24, issue 8, 2005, Pages 498~504
We introduce a Korean speech recognition platform (ECHOS) developed for education and research Purposes. ECHOS lowers the entry barrier to speech recognition research and can be used as a reference engine by providing elementary speech recognition modules. It has an easy simple object-oriented architecture, implemented in the C++ language with the standard template library. The input of the ECHOS is digital speech data sampled at 8 or 16 kHz. Its output is the 1-best recognition result. N-best recognition results, and a word graph. The recognition engine is composed of MFCC/PLP feature extraction, HMM-based acoustic modeling, n-gram language modeling, finite state network (FSN)- and lexical tree-based search algorithms. It can handle various tasks from isolated word recognition to large vocabulary continuous speech recognition. We compare the performance of ECHOS and hidden Markov model toolkit (HTK) for validation. In an FSN-based task. ECHOS shows similar word accuracy while the recognition time is doubled because of object-oriented implementation. For a 8000-word continuous speech recognition task, using the lexical tree search algorithm different from the algorithm used in HTK, it increases the word error rate by
relatively but reduces the recognition time to half.