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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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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 26, Issue 8 - Nov 2007
Volume 26, Issue 7 - Oct 2007
Volume 26, Issue 6 - Aug 2007
Volume 26, Issue 5 - Jul 2007
Volume 26, Issue 4 - May 2007
Volume 26, Issue 3 - Apr 2007
Volume 26, Issue 2 - Feb 2007
Volume 26, Issue 1 - Jan 2007
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Calculation and Uncertainty Estimation of the Volume of Reverberation Chamber with Indeterminate Form
Suh, Jae-Gap ; Suh, Sang-Joon ;
The Journal of the Acoustical Society of Korea, volume 26, issue 8, 2007, Pages 375~380
A reverberation chamber should be designed and constructed so as to satisfy its purposes and available space. However, it is somewhat difficult to meet the intended design requirements due to various errors from construction process. So, the post-construction measurement of its volume and surface areas is very essential to check the actual volume and volume uncertainty of a reverberation chamber These values should be carefully calculated and accurately estimated since they are used not only to evaluate the acoustic characteristics of building materials but also to calculate uncertainties for other acoustic characteristics. In this work, the method for the calculation and uncertainty estimation of the volume of a reverberation chamber is presented. To this end, the coordinates of all corners was measured with Total Station after construction. The results showed that the calculated volume of the measured reverberation chamber differs by 5 % from the design specification. The expanded volume uncertainty was also estimated to be about 2 % of the total calculated volume.
Shallow Water Acoustic Communication Channel Characteristic Analysis Using PN Sequence with 25 kHz Carrier at the Shore of Geojea Island
Kim, Jae-Gap ; Kim, Sea-Moon ; Lim, Young-Kon ;
The Journal of the Acoustical Society of Korea, volume 26, issue 8, 2007, Pages 381~389
In this paper, the measuring method of underwater acoustic communication channel characteristics in the shallow water using the autocorrelation characteristic of PN sequence and the undorwater communication channel analysis results from the received signal sample data are described. For measuring the underwater acoustic communication channel characteristics, two PN sequences are used as a transmitted data of I-channel and Q-channel of QPSK symbol and QPSK signal is transmitted with symbol rate of 5 kHz and carrier frequency of 25 kHz. In the receiver the received signal, which pass through 675 m and 1492 m, is sampled and then stored. Using the stored sample data, the scattering function, coherent time, delay power profile, spaced-tone autocorrelation function, delay spread, and coherent bandwidth of each propagation distance cases are analyzed. Based on the analysis results, several guidelines are suggested for the design and implementation of underwater transmission system.
Analysis and Implementation of Speech/Music Classification for 3GPP2 SMV Based on GMM
Song, Ji-Hyun ; Lee, Kye-Hwan ; Chang, Joon-Hyuk ;
The Journal of the Acoustical Society of Korea, volume 26, issue 8, 2007, Pages 390~396
In this letter, we propose a novel approach to improve the performance of speech/music classification for the selectable mode vocoder(SMV) of 3GPP2 using the Gaussian mixture model(GMM) which is based on the expectation-maximization(EM) algorithm. We first present an effective analysis of the features and the classification method adopted in the conventional SMV. And then feature vectors which are applied to the GMM are selected from relevant Parameters of the SMV for the efficient speech/music classification. The performance of the proposed algorithm is evaluated under various conditions and yields better results compared with the conventional scheme of the SMV.
Voice Activity Detection Based on SVM Classifier Using Likelihood Ratio Feature Vector
Jo, Q-Haing ; Kang, Sang-Ki ; Chang, Joon-Hyuk ;
The Journal of the Acoustical Society of Korea, volume 26, issue 8, 2007, Pages 397~402
In this paper, we apply a support vector machine(SVM) that incorporates an optimized nonlinear decision rule over different sets of feature vectors to improve the performance of statistical model-based voice activity detection(VAD). Conventional method performs VAD through setting up statistical models for each case of speech absence and presence assumption and comparing the geometric mean of the likelihood ratio (LR) for the individual frequency band extracted from input signal with the given threshold. We propose a novel VAD technique based on SVM by treating the LRs computed in each frequency bin as the elements of feature vector to minimize classification error probability instead of the conventional decision rule using geometric mean. As a result of experiments, the performance of SVM-based VAD using the proposed feature has shown better results compared with those of reported VADs in various noise environments.
A Unit Selection Methods using Flexible Break in a Japanese TTS
Song, Young-Hwan ; Na, Deok-Su ; Kim, Jong-Kuk ; Bae, Myung-Jin ; Lee, Jong-Seok ;
The Journal of the Acoustical Society of Korea, volume 26, issue 8, 2007, Pages 403~408
In a large corpus-based speech synthesizer, a break, which is a parameter influencing the naturalness and intelligibility, is used as an important feature during a unit selection process. Japanese is a language having intonations, which ate indicated by the relative differences in pitch heights and the APs(Accentual Phrases) are placed according to the changes of the accents while a break occurs on a boundary of the APs. Although a break can be predicted by using J-ToBI(Japanese-Tones and Break Indices), which is a rule-based or statistical approach, it is very difficult to predict a break exactly due to the flexibility. Therefore, in this paper, a method is to conduct a unit search by dividing breaks into two types, such as a fixed break and a flexible break, in order to use the advantages of a large-scale corpus, which includes various types of prosodies. As a result of an experiment, the proposed unit selection method contributed itself to enhance the naturalness of synthesized speeches.
Enhancement of Ultrasonic Sonoluminescence Image Using Digital Image Processing
Kim, Jung-Soon ; Jo, Mi-Sun ; Mun, Kwan-Ho ; Ha, Kang-Lyeol ; Jun, Byung-Doo ; Kim, Moo-Joon ;
The Journal of the Acoustical Society of Korea, volume 26, issue 8, 2007, Pages 409~414
In spite of many studies of the acoustic field visualization by using sonoluminescence phenomena, the visualization method has not been used widely because it needs high acoustic intensity to get the luminescence intensity enough to observe. Recently, the digital camera with high resolution and big memory makes it possible to get the digital image data even though the brightness of the image is too weak to observe with naked eyes. In this study we investigated the variation of sonoluminescence intensity with the acoustic intensity from an ultrasonic transducer. From this result, the inverse function, which makes the tendency of the variation to linear, was obtained. Using the order of the inverse function, we can expect a matching function. Applying the matching function to digital image data, the distribution of the histogram could be controlled appropriately and the image from relatively weak acoustic intensity could be enhanced by the method.
A Study on Underwater Source Localization Using the Wideband Interference Pattern Matching
Chun, Seung-Yong ; Kim, Se-Young ; Kim, Ki-Man ;
The Journal of the Acoustical Society of Korea, volume 26, issue 8, 2007, Pages 415~425
This paper proposes a method of underwater source localization using the wideband interference patterns matching. By matching two interference patterns in the spectrogram, it is estimated a ratio of the range from source to sensor5, and then this ratio is applied to the Apollonius circle. The Apollonius circle is defined as the locus of all points whose distances from two fixed points are in a constant value so that it is possible to represent the locus of potential source location. The Apollonius circle alone, however still keeps the ambiguity against the correct source location. Therefore another equation is necessary to estimate the unique locus of the source location. By estimating time differences of signal arrivals between source and sensors, the hyperbola equation is used to get the cross point of the two equations, where the point being assumed to be the source position. Simulations are performed to get performances of the proposed algorithm. Also, comparisons with real sea experiment data are made to prove applicability of the algorithm in real environment. The results show that the proposed algorithm successfully estimates the source position within an error bound of 10%.
MIMO Vector Channel Modeling and Performance Analysis in Underwater Channel Environments
Lee, Deok-Hwan ; Ko, Hak-Lim ; Lim, Yong-Kon ;
The Journal of the Acoustical Society of Korea, volume 26, issue 8, 2007, Pages 426~431
In this paper we have studied the underwater vector channel modeling for MIMO(Multiple Input Multiple Output) to increase the performance and efficiency for ultrasound communication in underwater channel environments. Also we have analyzed the MIMO techniques using the proposed channel modeling. For underwater MIMO channel modeling. experiments were done in real channel environments and the data were analyzed to estimate parameters such as fading, Doppler, time delay, angle of arrival, and receiving power. These were used for modeling of underwater vector channel modeling for MIMO. Additionally, we have analyzed the performance of MIMO systems using our proposed channel models. As a result we could see that the BER has decreased severely with the same SNR when using the MIMO system.