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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 28, Issue 8 - Nov 2009
Volume 28, Issue 7 - Oct 2009
Volume 28, Issue 6 - Aug 2009
Volume 28, Issue 5 - Jul 2009
Volume 28, Issue 4 - May 2009
Volume 28, Issue 3 - Apr 2009
Volume 28, Issue 2 - Feb 2009
Volume 28, Issue 1 - Jan 2009
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Design of Isolation-Type Matching Network for Underwater Acoustic Piezoelectric Transducer Using Chebyshev Filter Function
Lee, Jeong-Min ; Lee, Byung-Hwa ; Baek, Kwang-Ryul ;
The Journal of the Acoustical Society of Korea, volume 28, issue 6, 2009, Pages 491~498
This paper presents the design method of an impedance matching network using an isolation transformer and the Chebyshev filter function for the high efficiency and the flat power driving of an underwater acoustic piezoelectric transducer. The proposed impedance matching network is designed for minimizing the reactance component of transducer and having the flat power response in the wide frequency range. We design a low pass filter with ladder-type circuit using the Chebyshev function as standard prototype filter function. In addition, we design the impedance matching network which is suitable for the equivalent circuit of transducer and the turn ratio of transformer through the bandpass frequency transformation. The proposed method is applied to the simulated dummy load of the tonpilz-type transducer operating in the middle frequency range. The simulation results are compared with the measured characteristics and the validity of the proposed method is verified.
MAC Protocol for Single-Hop Underwater Sensor Network
Baek, Seung-Kwon ; Cho, Ho-Shin ; Jang, Youn-Seon ;
The Journal of the Acoustical Society of Korea, volume 28, issue 6, 2009, Pages 499~505
Main design issues for MAC (Medium Access Control) protocol in underwater sensor networks are long propagation delay caused by the low speed of sound, difficult synchronization, and energy-limited node's life. We aimed to mitigate the problems of strict synchronization and channel inefficiency of TDMA and also the throughput degradation induced by unavoidable collisions in contention based MAC protocols. This proposed protocol improved not only the energy efficiency by adopting a sleep-mode, but also the throughput by reducing collisions and increasing channel efficiency.
Analysis of Capacity for Bi-Directional Coding Applying Time Reversal Technique in Underwater Acoustic Channel
Kim, Hyeon-Su ; Kwon, Yang-Soo ; Yoo, Jae-Ho ; Chung, Jae-Hak ; Kim, Seong-Il ;
The Journal of the Acoustical Society of Korea, volume 28, issue 6, 2009, Pages 506~513
In this paper, we propose a bi-directional communication method applying time reversal technique in underwater acoustic channel in order to exchange data between sensor nodes with an available relay node. The proposed method reduces the conventional 4-step relaying procedure to 2-step and improves the system capacity. Moreover, it increases transmission range efficiently while the relay node can be implemented with low complexity. Simulation results demonstrate that the proposed scheme achieves 3.2 bps/Hz higher capacity than that of the conventional method at SNR 20 dB.
Orthonormalized Forward Backward PAST (Projection Approximation Subspace Tracking) Algorithm
Lim, Jun-Seok ;
The Journal of the Acoustical Society of Korea, volume 28, issue 6, 2009, Pages 514~519
The projection approximation subspace tracking (PAST) is one of the attractive subspace tracking algorithms, because it estimates the signal subspace adaptively and continuously. Furthermore, the computational complexity is relatively low. However, the algorithm still has room for improvement in the subspace estimation accuracy. FE-PAST (Forward-Backward PAST) is one of the results from the improvement studies. In this paper, we propose a new algorithm to improve the orthogonality of the FB-PAST (Forward-Backward PAST).
MAFF-RLS Broadband Microphone GSC for Non-Stationary Interference Cancellation
Lee, Seok-Jin ; Lim, Jun-Seok ; Sung, Koeng-Mo ;
The Journal of the Acoustical Society of Korea, volume 28, issue 6, 2009, Pages 520~525
The conventional studies about an adaptive beamformer assumed that the interference signals are stationary, so they used time-average of signals or Least Mean Squares. However, these methods showed low performance of canceling the non-stationary interferences. In this paper, the MAFF-RLS algorithm is developed in order to cancel non-stationary interferences, and the GSC structure using this algorithm is proposed. Furthermore, the performance of the MAFF-RLS beamformer is verified by simulation using MATLAB. This simulation results show the performance of the proposed beamformer is better than that of the SMI and the conventional RLS beamformer.
Formant Synthesis of Haegeum Sounds Using Cepstral Envelope
Hong, Yeon-Woo ; Cho, Sang-Jin ; Kim, Jong-Myon ; Chong, Ui-Pil ;
The Journal of the Acoustical Society of Korea, volume 28, issue 6, 2009, Pages 526~533
This paper proposes a formant synthesis method of Haegeum sounds using cepstral envelope for spectral modeling. Spectral modeling synthesis (SMS) is a technique that models time-varying spectra as a combination of sinusoids (the "deterministic" part), and a time-varying filtered noise component (the "stochastic" part). SMS is appropriate for synthesizing sounds of string and wind instruments whose harmonics are evenly distributed over whole frequency band. Formants extracted from cepstral envelope are parameterized for synthesis of sinusoids. A resonator by Impulse Invariant Transform (IIT) is applied to synthesize sinusoids and the results are bandpass filtered to adjust magnitude. The noise is calculated by first generating the sinusoids with formant synthesis, subtracting them from the original sound, and then removing some harmonics remained. Linear interpolation is used to model noise. The synthesized sounds are made by summing sinusoids, which are shown to be similar to the original Haegeum sounds.
A Study of Psychometric Function Curve for Korean Standard Monosyllabic Word Lists for Preschoolers (KS-MWL-P)
Shin, Hyun-Wook ; Kim, Jin-Sook ;
The Journal of the Acoustical Society of Korea, volume 28, issue 6, 2009, Pages 534~541
Word recognition test (WRT) for the children can be useful for diagnosing the degree of communication disability, prescribing hearing instruments, planning aural rehabilitation and speech therapy, and determination of site of lesions. The Korean standard monosyllabic word lists for preschoolers (KS-MWL-P) were developed considering the criteria given by the literatures. However, the authors of KS-MWL-P suggested more children should be included to verify homogeneity of the lists using psychometric function curve since only 8 children participated in the developing process. The purpose of this study was to explore the homogeneity of KS-MWL-P for supplementing the limitations of the lists employing psychometric analysis. To 23 preschoolers who have normal-hearing, 100 monosyllabic KS-MWL-P words were examined with the pictures. Psychometric function curve with linear slopes of 20% and 80%'s correct rates through accounting recognition scores of each monosyllabic word at variable intensities from -10 to 40 dBHL was obtained and analyzed. As a result, s-shaped psychometric function curve was presented with increasing correct rate depending on intensity and showed no statistical significant differences among each word and list. The congruous graph shapes among lists also indicated good homogeneity and the list 1,2,3,4's average slopes were 4.48, 3.86, 4.65, 4.50. It was verified that the homogeneity was suitable because the analysis of variance showed no statistical significance among lists (p>0.05). However, KS-MWL-P's order of slope according to the order of the number of items,
showed no difference with the p-value of 0.93, 0.59, 0.91, 0.70 for the lists 1,2,3, and 4, respectively. Although KS-MWL-P was assumed that the lower-numbered items were easy for testing younger ages, this study's results could not agree with the author's conclusion. Considering this matter, rearranging of the number of items should be performed according to the analysis of slope suggested by this study for testing younger children with easier items. Other than this, in conclusion, KS-MWL-P was proved to be useful for clinical and rehabilitative evaluating and training tools for preschoolers.
Correlations of Lumbar and Femoral Bone Mineral Densities with Calcaneal Speed of Sound in Osteoporotic Woman
Lee, Kang-Il ; Choi, Min-Joo ;
The Journal of the Acoustical Society of Korea, volume 28, issue 6, 2009, Pages 542~547
In this in vivo study, correlations of lumbar and femoral bone mineral densities (BMDs) with calcaneal speed of sound (SOS) were investigated in 36 osteoporotic women. Areal BMDs of the L2-L4 lumbar spine and the right femoral neck were measured by using dual energy X-ray absorptiometry (DEXA). SOS of the right calcaneus was measured by using ultrasound bone densitometry. Pearson's correlation coefficient (r) and level of significance (p) were used to evaluate the correlations between measurements. Lumbar BMD was highly correlated with femoral BMD (r=0.81). Lumbar and femoral BMDs exhibited similar comparable negative correlations with age (r=-0.52 and r=-0.55). A moderate negative correlation was found between calcaneal SOS and age (r=-0.45). Calcaneal SOS was significantly correlated with lumbar and femoral BMDs, with a higher correlation with femoral BMD rather than with lumbar BMD (r=0.54 and r=0.62). However, calcaneal SOS may not be an optimum index for the estimation of BMD of the most important fracture sites, such as the lumbar and the femur, because it showed lower correlations with lumbar and femoral BMDs compared to that with calcaneal BMD. Therefore, the development of a quantitative ultrasound technology for the direct measurement of acoustic properties at the lumbar and the femur is required to estimate BMD of these sites more accurately.
A Speaker Array System for Sound Spotlight in a Reverberant Environment
Baek, Soon-Ho ; Song, Myung-Suk ; Kang, Hong-Goo ; Lee, Seok-Pil ;
The Journal of the Acoustical Society of Korea, volume 28, issue 6, 2009, Pages 548~556
This paper proposes an efficient speaker array system to spotlight a sound into a target position in a reverberant environment. The proposed method introduces a criterion of maximizing the energy of system response from each channel to the target position. Simulation results with a sixteen channel speaker array system prove that the performance of the proposed method improves that of the conventional method that uses a broadband beamformer in a reverberant environment.
A Study on Enhancement of 3D Sound Using Improved HRTFS
Koo, Kyo-Sik ; Cha, Hyung-Tai ;
The Journal of the Acoustical Society of Korea, volume 28, issue 6, 2009, Pages 557~565
To perceive the direction and the distance of a sound, we always use a couple of information. Head Related Transfer Function (HRTF) contains the information that sound arrives from a sound source to the ears of the listener, like differences of level, phase and frequency spectrum. For a reproduction system using 2 channels, we apply HRTF to many algorithms which make 3d sound. But it causes a problem to localize a sound source around a certain places which is called the cone-of-confusion. In this paper, we proposed the new algorithm to reduce the confusion of sound image localization. The difference of frequency spectrum and psychoacoustics theory are used to boost the spectral cue among each directions. To confirm the performance of the algorithm, informal listening tests are carried out. As a result, we can make the improved 3d sound in 2 channel system based on a headphone. Also sound quality of improved 3d sound is much better than conventional methods.
Simultaneous Speaker and Environment Adaptation by Environment Clustering in Various Noise Environments
Kim, Young-Kuk ; Song, Hwa-Jeon ; Kim, Hyung-Soon ;
The Journal of the Acoustical Society of Korea, volume 28, issue 6, 2009, Pages 566~571
This paper proposes noise-robust fast speaker adaptation method based on the eigenvoice framework in various noisy environments. The proposed method is focused on de-noising and environment clustering. Since the de-noised adaptation DB still has residual noise in itself, environment clustering divides the noisy adaptation data into similar environments by a clustering method using the cepstral mean of non-speech segments as a feature vector. Then each adaptation data in the same cluster is used to build an environment-clustered speaker adapted (SA) model. After selecting multiple environmentally clustered SA models which are similar to test environment, the speaker adaptation based on an appropriate linear combination of clustered SA models is conducted. According to our experiments, we observe that the proposed method provides error rate reduction of
over baseline with speaker independent model.
A DB Pruning Method in a Large Corpus-Based TTS with Multiple Candidate Speech Segments
Lee, Jung-Chul ; Kang, Tae-Ho ;
The Journal of the Acoustical Society of Korea, volume 28, issue 6, 2009, Pages 572~577
Large corpus-based concatenating Text-to-Speech (TTS) systems can generate natural synthetic speech without additional signal processing. To prune the redundant speech segments in a large speech segment DB, we can utilize a decision-tree based triphone clustering algorithm widely used in speech recognition area. But, the conventional methods have problems in representing the acoustic transitional characteristics of the phones and in applying context questions with hierarchic priority. In this paper, we propose a new clustering algorithm to downsize the speech DB. Firstly, three 13th order MFCC vectors from first, medial, and final frame of a phone are combined into a 39 dimensional vector to represent the transitional characteristics of a phone. And then the hierarchically grouped three question sets are used to construct the triphone trees. For the performance test, we used DTW algorithm to calculate the acoustic similarity between the target triphone and the triphone from the tree search result. Experimental results show that the proposed method can reduce the size of speech DB by 23% and select better phones with higher acoustic similarity. Therefore the proposed method can be applied to make a small sized TTS.