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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 32, Issue 6 - Nov 2013
Volume 32, Issue 5 - Sep 2013
Volume 32, Issue 4 - Jul 2013
Volume 32, Issue 3 - May 2013
Volume 32, Issue 2 - Mar 2013
Volume 32, Issue 1 - Jan 2013
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Performance Evaluation of Underwater Acoustic Communication in Frequency Selective Shallow Water
Park, Kyu-Chil ; Park, Jihyun ; Lee, Seung Wook ; Jung, Jin Woo ; Shin, Jungchae ; Yoon, Jong Rak ;
The Journal of the Acoustical Society of Korea, volume 32, issue 2, 2013, Pages 95~103
DOI : 10.7776/ASK.2013.32.2.095
An underwater acoustic (UWA) communication in shallow water is strongly affected by the water surface and the seabed acoustical properties. Every reflected signal to receiver experiences a time-variant scattering in sea surface roughness and a grazing-angle-dependent reflection loss in bottom. Consequently, the performance of UWA communication systems is degraded, and high-speed digital communication is disrupted. If there is a dominant signal path such as a direct path, the received signal is modeled statistically as Rice fading but if not, it is modeled as Rayleigh fading. However, it has been known to be very difficult to reproduce the statistical estimation by real experimental evaluation in the sea. To give an insight for this scattering and grazing-angle-dependent bottom reflection loss effect in UWA communication, authors conduct experiments to quantify these effects. The image is transmitted using binary frequency shift keying (BFSK) modulation. The quality of the received image is shown to be affected by water surface scattering and grazing-angle-dependent bottom reflection loss. The analysis is based on the transmitter to receiver range and the receiver depth dependent image quality and bit error rate (BER). The results show that the received image quality is highly dependent on the transmitter-receiver range and receiver depth which characterizes the channel coherence bandwidth.
High-frequency Reverberation Simulation of High-speed Moving Source in Range-independent Ocean Environment
Kim, Sunhyo ; Lee, Wonbyoung ; You, Seung-Ki ; Choi, Jee Woong ; Kim, Wooshik ; Park, Joung Soo ; Park, Kyoung Ju ;
The Journal of the Acoustical Society of Korea, volume 32, issue 2, 2013, Pages 104~115
DOI : 10.7776/ASK.2013.32.2.104
In a shallow water waveguide, reverberation signals and their Doppler effects form the primary limitation on sonar system performance. Therefore, in the reverberation-limited environment, it is necessary to estimate the reverberation level to be encountered under the conditions in which the sonar system is operated. In this paper, high-frequency reverberation model capable of simulating the reverberation signals received by a high-speed moving source in a range independent waveguide is suggested. In this model, eigenray information from the source to each boundary is calculated using the ray-based approach and the optimizing method for the launch angles. And the source receiving position changed by the moving source is found by a scattering path-finding algorithm, which considers the speed and direction of source and sound speed to find the path of source movement. The scattering effects from sea surface and bottom boundaries are considered by APL-UW scattering models. The model suggested in this paper is verified by a comparison to the measurements made in August 2010. Lastly, this model reflects well statistical properties of the reverberation signals.
Underwater Acoustic Communication Channel Modeling Regarding Magnitude Fluctuation Based on Ocean Surface Scattering Theory and BELLHOP Ray Model and Its Application to Passive Time-reversal Communication
Kim, Joonsuk ; Koh, Il-Suek ; Lee, Yongshik ;
The Journal of the Acoustical Society of Korea, volume 32, issue 2, 2013, Pages 116~123
DOI : 10.7776/ASK.2013.32.2.116
This paper represents generation of time-varying underwater acoustic channels by performing scattering simulation with time-varying ocean surface and Kirchhoff approximation. In order to estimate the time-varying ocean surface, 1D Pierson-Moskowitz ocean power spectrum and Gaussian correlation function were used. The computed scattering coefficients are applied to the amplitudes of each impulse of BELLHOP simulation result. The scattering coefficients are then compared with measured doppler spectral density of signal components which were scattered from ocean surface and the correlation time used in the Gaussian correlation function was estimated by the comparison. Finally, bit-error-rate and channel correlation simulations were performed with the generated time-varying channel based on passive time-reversal communication scenario.
Performance Analysis of Underwater Acoustic Communication Systems with Turbo Equalization in Korean Littoral Sea
Park, Tae-Doo ; Han, Jeong-Woo ; Jung, Ji-Won ; Kim, Ki-Man ; Lee, Sang-Kook ; Chun, Seung-Yong ; Son, Kweon ;
The Journal of the Acoustical Society of Korea, volume 32, issue 2, 2013, Pages 124~130
DOI : 10.7776/ASK.2013.32.2.124
The performance of underwater acoustic communication system is sensitive to the ISI(Inter-Symbol Interference) due to delay spread develop of multipath signal propagation. The equalizer is used to combat the ISI. In this paper, the performances of underwater acoustic communication with turbo equalizer were evaluated by real data collected in Korean littoral sea. As a result, when one iterative decoding using turbo equalizer is applied, the performance was improved 1.5 dB than the case of the non-iterative equalizer at BER
. In the case of two or three iterations the performance was enhanced about 3.5 dB, but the performance wasn't improved any more in the case of more than three times.
Signal Subspace-based Voice Activity Detection Using Generalized Gaussian Distribution
Um, Yong-Sub ; Chang, Joon-Hyuk ; Kim, Dong Kook ;
The Journal of the Acoustical Society of Korea, volume 32, issue 2, 2013, Pages 131~137
DOI : 10.7776/ASK.2013.32.2.131
In this paper we propose an improved voice activity detection (VAD) algorithm using statistical models in the signal subspace domain. A uncorrelated signal subspace is generated using embedded prewhitening technique and the statistical characteristics of the noisy speech and noise are investigated in this domain. According to the characteristics of the signals in the signal subspace, a new statistical VAD method using GGD (Generalized Gaussian Distribution) is proposed. Experimental results show that the proposed GGD-based approach outperforms the Gaussian-based signal subspace method at 0-15 dB SNR simulation conditions.
Multiband Enhancement for DEMON Processing Algorithms
Cheong, Myoung Jun ; Hwang, Soo Bok ; Lee, Seung Woo ; Kim, Jin Seok ;
The Journal of the Acoustical Society of Korea, volume 32, issue 2, 2013, Pages 138~146
DOI : 10.7776/ASK.2013.32.2.138
Passive sonars employ DEMON (Detection of Envelope Modulation on Noise) processing to extract propeller information from the radiated noise of underwater targets. Conventional DEMON processing improves SNR(Signal to Noise Ratio) characteristic by Welch method. The conventional Welch method overlaps several different time domain DEMON outputs to reduce the variance. However, the conventional methods have high computational complexity to get high SNR with correlated acoustic signals. In this paper, we propose new DEMON processing method that divides acoustic signal into several frequency bands before DEMON processing and averages each DEMON outputs. Therefore, the proposed method gathers independent acoustic signal faster than conventional method with low computational complexity. We prove the performance of the proposed method with mathematical analysis and computer simulations.
Robust Speech Endpoint Detection in Noisy Environments for HRI (Human-Robot Interface)
Park, Jin-Soo ; Ko, Han-Seok ;
The Journal of the Acoustical Society of Korea, volume 32, issue 2, 2013, Pages 147~156
DOI : 10.7776/ASK.2013.32.2.147
In this paper, a new speech endpoint detection method in noisy environments for moving robot platforms is proposed. In the conventional method, the endpoint of speech is obtained by applying an edge detection filter that finds abrupt changes in the feature domain. However, since the feature of the frame energy is unstable in such noisy environments, it is difficult to accurately find the endpoint of speech. Therefore, a novel feature extraction method based on the twice-iterated fast fourier transform (TIFFT) and statistical models of speech is proposed. The proposed feature extraction method was applied to an edge detection filter for effective detection of the endpoint of speech. Representative experiments claim that there was a substantial improvement over the conventional method.
Non-Intrusive Speech Quality Estimation of G.729 Codec using a Packet Loss Effect Model
Lee, Min-Ki ; Kang, Hong-Goo ;
The Journal of the Acoustical Society of Korea, volume 32, issue 2, 2013, Pages 157~166
DOI : 10.7776/ASK.2013.32.2.157
This paper proposes a non-intrusive speech quality estimation method considering the effects of packet loss to perceptual quality. Packet loss is a major reason of quality degradation in a packet based speech communications network, whose effects are different according to the input speech characteristics or the performance of the embedded packet loss concealment (PLC) algorithm. For the quality estimation system that involves packet loss effects, we first observe the packet loss of G.729 codec which is one of narrowband codec in VoIP system. In order to quantify the lost packet affects, we design a classification algorithm only using speech parameters of G.729 decoder. Then, the degradation values of each class are iteratively selected that maximizes the correlation with the degradation PESQ-LQ scores, and total quality degradation is modeled by the weighted sum. From analyzing the correlation measures, we obtained correlation values of 0.8950 for the intrusive model and 0.8911 for the non-intrusive method.
Classification of Diphthongs using Acoustic Phonetic Parameters
Lee, Suk-Myung ; Choi, Jeung-Yoon ;
The Journal of the Acoustical Society of Korea, volume 32, issue 2, 2013, Pages 167~173
DOI : 10.7776/ASK.2013.32.2.167
This work examines classification of diphthongs, as part of a distinctive feature-based speech recognition system. Acoustic measurements related to the vocal tract and the voice source are examined, and analysis of variance (ANOVA) results show that vowel duration, energy trajectory, and formant variation are significant. A balanced error rate of 17.8% is obtained for 2-way diphthong classification on the TIMIT database, and error rates of 32.9%, 29.9%, and 20.2% are obtained for /aw/, /ay/, and /oy/, for 4-way classification, respectively. Adding the acoustic features to widely used Mel-frequency cepstral coefficients also improves classification.
Decision Tree Based Context Clustering with Cross Likelihood Ratio for HMM-based TTS
Jung, Chi-Sang ; Kang, Hong-Goo ;
The Journal of the Acoustical Society of Korea, volume 32, issue 2, 2013, Pages 174~180
DOI : 10.7776/ASK.2013.32.2.174
This paper proposes a decision tree based context clustering algorithm for HMM-based speech synthesis systems using the cross likelihood ratio with a hierarchical prior (CLRHP). Conventional algorithms tie the context-dependent HMM states that have similar statistical characteristics, but they do not consider the statistical similarity of split child nodes, which does not guarantee the statistical difference between the final leaf nodes. The proposed CLRHP algorithm improves the reliability of model parameters by taking a criterion of minimizing the statistical similarity of split child nodes. Experimental results verify the superiority of the proposed approach to conventional ones.
Effect of Cortical Bone on Acoustic Properties of Trabecular Bone in Bovine Femur In Vitro
Hwang, Kyo Seung ; Lee, Kang Il ;
The Journal of the Acoustical Society of Korea, volume 32, issue 2, 2013, Pages 181~189
DOI : 10.7776/ASK.2013.32.2.181
The purpose of the present study is to investigate the effect of cortical bone on acoustic properties of trabecular bone, such as speed of sound (SOS) and normalized broadband ultrasound attenuation (nBUA), in bovine femur in vitro. Twelve trabecular bone samples and three cortical bone plates with thicknesses of 1.00, 1.47, and 2.00 mm were extracted from the proximal end of two bovine femurs. The correlations between acoustic properties and trabecular apparent bone density were also examined before and after attaching a cortical bone plate to the trabecular bone samples. SOS increased linearly with increasing thickness of the cortical plate attached to one side of ultrasonic incidence of the trabecular bone samples, whereas nBUA showed a nonlinear dependence on the thickness of the cortical plate. All the SOS (r = 0.95-0.97) and nBUA (r = 0.53-0.73) measurements with and without the cortical bone plate with various thicknesses were found to exhibit high correlations with the trabecular apparent bone density. These results imply that the acoustic properties measured in the femur with lateral cortical layers in vitro can be useful indices for the prediction of trabecular bone mineral density.