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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 34, Issue 6 - Nov 2015
Volume 34, Issue 5 - Sep 2015
Volume 34, Issue 4 - Jul 2015
Volume 34, Issue 3 - May 2015
Volume 34, Issue 2 - Mar 2015
Volume 34, Issue 1 - Jan 2015
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Acoustic Identification of Inner Materials in a Single-layer Cylindrical Shell with Resonance Scattering Theory
Jo, Young-Tae ; Kim, Wan-Gu ; Yoon, Suk Wang ;
The Journal of the Acoustical Society of Korea, volume 34, issue 4, 2015, Pages 257~263
DOI : 10.7776/ASK.2015.34.4.257
Acoustic identification of inner materials in a single-layer cylindrical shell is investigated with acoustic resonance theory. The theoretical resonance peak frequencies for a cylindrical shell are little affected by the density variation, but remarkably changed by the sound speed variation of inner materials. Such acoustic dependency can be utilized to identify inner materials in a cylindrical shell. Acoustic resonance spectrogram for a single-layer cylindrical shell is theoretically plotted as functions of normalized frequency and sound speed of inner materials. The inner materials can be acoustically identified by overlapping acoustic resonance peaks from measured backscattering sound field on the spectrogram. To experimentally confirm this method, backscattering sound field of cylindrical shell filled with water, oil or ethylene glycol was measured in water tank. The inner materials could be identified by acoustic resonance peaks of the backscattering sound field monostatically measured with a transduce of 1.05 MHz center frequency.
Improvement of the Radiation Beam Profile of a Medical Ultrasonic Transducer
Park, Yeonsue ; Lee, Wonseok ; Roh, Yongrae ;
The Journal of the Acoustical Society of Korea, volume 34, issue 4, 2015, Pages 264~273
DOI : 10.7776/ASK.2015.34.4.264
Improvement of the radiation beam profile of a medical ultrasonic transducer has been researched in this paper. In order to improve the beam profile, a new transducer structure has been devised that includes both a shaded electrode and a multi-focus lens. For a linear sound source, the beam profile was investigated through finite element analysis, and then the optimal design of the devised structure was carried out by considering such performances as sidelobe level, focal range and beamwidth simultaneously. In the process, the optimal dimension of the devised structure was derived by using the ratio of the focal range to the minimum beamwidth as a performance index. As a result, the beam profile has been improved to have a lower sidelobe level at -20.2 dB and a consistent narrow beamwidth from 30 mm to 160 mm depth with the minimum beamwidth at 2.04 mm. Further, a prototype transducer was fabricated to have the devised structure, and its performance was measured and compared with the analysis results to confirm the validity of the devised transducer structure.
Evaluation and Analysis of Awareness in Noise-induced Hearing Loss Using Survey
Lee, Donguk ; Yu, Jyaehyung ; Han, Woojae ;
The Journal of the Acoustical Society of Korea, volume 34, issue 4, 2015, Pages 274~281
DOI : 10.7776/ASK.2015.34.4.274
Although noise-induced hearing loss (NIHL) is a significant public health problem, many people might not be aware that exposure to loud noise could occur hearing loss. The purpose of this study is to evaluate and analyze how importantly and seriously people are aware of NIHL using a 22-question survey. It was administered to random 150 people including between 20 s to 60 s. The questionnaire contained questions about i) views toward general health issues including hearing loss and tinnitus, ii) noise exposure, and iii) views toward hearing protection. Results showed that hearing loss was defined on a likert scale as 'a very big problem' by 17.33 % of respondents compared with other health issues. Surprisingly, most respondents (82 %) had not heard, read, or seen anything lately related to the issue of hearing loss. Many respondents had experience hearing problem or tinnitus under loud noise situations (85 %), however, only 11.33 % of respondents had used earplugs. Fortunately, many could be motivated to try ear protection if they were advised by a medical professional (80 %) or were aware of the potential for permeant hearing loss (78.67 %). We concluded that awareness of the potential for permanent hearing loss with noise and effective methods of hearing protection should be announced to public for preventing NIHL.
Experimental Investigation of Factors Influencing Chair Absorption Characteristics
Choi, Young-Ji ; Koo, JaeOh ;
The Journal of the Acoustical Society of Korea, volume 34, issue 4, 2015, Pages 282~287
DOI : 10.7776/ASK.2015.34.4.282
This paper examines the combinations of factors influencing the absorption characteristics of theatre chairs. One-tenth scale model chairs and listeners that closely approximated the absorption characteristics of full scale theatre chairs were used to measure the interactive effects of the test variables on the chairs absorption characteristics. The test variables were the type of chairs, the row spacing, as well as the presence of people and carpet. The variations of absorption increments with varied row spacing tended to be smallest when the chairs were less absorptive, i.e. with less carpet or occupants. The incremental effects of adding occupants or carpet averaged over three row spacings varied over frequency.
Applied Sound Frequency Monitoring in the Transformer Oil Using Fiber Optic Sagnac Interferometer
Lee, Jongkil ; Lee, Seunghong ;
The Journal of the Acoustical Society of Korea, volume 34, issue 4, 2015, Pages 288~294
DOI : 10.7776/ASK.2015.34.4.288
The fiber optic Sagnac interferometer is well established as a sensor for detection of physical perturbations such as acoustic and vibration. In this paper acoustic signals generated in the cylindrical cavity submerged in transformer oil were measured by the fiber optic sensor array in one Sagnac loop. Two different external sound frequencies,
, were applied to the sensor array simultaneously by using piezoelectric with frequency range from 5 kHz to 90 kHz. Based on the experimental results, fiber optic sensor detected harmonic series of applied sound frequency such as
. Suggested fiber optic sensor array can be applied to monitor physical quantities such as internal sound pressure and vibration due to partial discharge in the real electric transformer system.
An Efficient Decoding Method for High Throughput in Underwater Communication
Baek, Chang-Uk ; Jung, Ji-Won ; Chun, Seung-Yong ; Kim, Woo-Sik ;
The Journal of the Acoustical Society of Korea, volume 34, issue 4, 2015, Pages 295~302
DOI : 10.7776/ASK.2015.34.4.295
Acoustic channels are characterized by long multipath spreads that cause inter-symbol interference. The way in which this fact influences the design of the receiver structure is considered. To satisfy performance and throughput, we presented consecutive iterative BCJR (Bahl, Cocke, Jelinek, Raviv) equalization to improve the performance and throughput. To achieve low error performance, we resort to powerful BCJR equalization algorithms that iteratively update probabilistic information between inner decoder and outer decoder. Also, to achieve high throughput, we divide long packet into consecutive small packets, and the estimate channel information of previous packets are compensated to next packets. Based on experimental channel response, we confirmed that the performance is improved for long length packet size.
Local Distribution Based Density Clustering for Speaker Diarization
Rho, Jinsang ; Shon, Suwon ; Kim, Sung Soo ; Lee, Jae-Won ; Ko, Hanseok ;
The Journal of the Acoustical Society of Korea, volume 34, issue 4, 2015, Pages 303~309
DOI : 10.7776/ASK.2015.34.4.303
Speaker diarization is the task of determining the speakers for unlabeled data, and DBSCAN (Density-Based Spatial Clustering of Applications with Noise) has been widely used in the field of speaker diarization for its simplicity and computational efficiency. One challenging issue, however, is that if different clusters in non-spatial dataset are adjacent to each other, over-clustering may occur which subsequently degrades the performance of DBSCAN. In this paper, we identify the drawbacks of DBSCAN and propose a new density clustering algorithm based on local distribution property around object. Variable density criterions for local density and spreadness of object are used for effective data clustering. We compare the proposed algorithm to DBSCAN in terms of clustering accuracy. Experimental results confirm that the proposed algorithm exhibits higher accuracy than DBSCAN without over-clustering and confirm that the new approach based on local density and object spreadness is efficient.
A Parametric Voice Activity Detection Based on the SPD-TE for Nonstationary Noises
Koo, Boneung ;
The Journal of the Acoustical Society of Korea, volume 34, issue 4, 2015, Pages 310~315
DOI : 10.7776/ASK.2015.34.4.310
A single channel VAD (Voice Activity Detection) algorithm for nonstationary noise environment is proposed in this paper. Threshold values of the feature parameter for VAD decision are updated adaptively based on estimates of means and standard deviations of past non-speech frames. The feature parameter, SPD-TE (Spectral Power Difference-Teager Energy), is obtained by applying the Teager energy to the WPD (Wavelet Packet Decomposition) coefficients. It was reported previously that the SPD-TE is robust to noise as a feature for VAD. Experimental results by using TIMIT speech and NOISEX-92 noise databases show that decision accuracy of the proposed algorithm is comparable to several typical VAD algorithms including standards for SNR values ranging from 10 to -10 dB.
Cepstral Feature Normalization Methods Using Pole Filtering and Scale Normalization for Robust Speech Recognition
Choi, Bo Kyeong ; Ban, Sung Min ; Kim, Hyung Soon ;
The Journal of the Acoustical Society of Korea, volume 34, issue 4, 2015, Pages 316~320
DOI : 10.7776/ASK.2015.34.4.316
In this paper, the pole filtering concept is applied to the Mel-frequency cepstral coefficient (MFCC) feature vectors in the conventional cepstral mean normalization (CMN) and cepstral mean and variance normalization (CMVN) frameworks. Additionally, performance of the cepstral mean and scale normalization (CMSN), which uses scale normalization instead of variance normalization, is evaluated in speech recognition experiments in noisy environments. Because CMN and CMVN are usually performed on a per-utterance basis, in case of short utterance, they have a problem that reliable estimation of the mean and variance is not guaranteed. However, by applying the pole filtering and scale normalization techniques to the feature normalization process, this problem can be relieved. Experimental results using Aurora 2 database (DB) show that feature normalization method combining the pole-filtering and scale normalization yields the best improvements.
Visual Voice Activity Detection and Adaptive Threshold Estimation for Speech Recognition
Song, Taeyup ; Lee, Kyungsun ; Kim, Sung Soo ; Lee, Jae-Won ; Ko, Hanseok ;
The Journal of the Acoustical Society of Korea, volume 34, issue 4, 2015, Pages 321~327
DOI : 10.7776/ASK.2015.34.4.321
In this paper, we propose an algorithm for achieving robust Visual Voice Activity Detection (VVAD) for enhanced speech recognition. In conventional VVAD algorithms, the motion of lip region is found by applying an optical flow or Chaos inspired measures for detecting visual speech frames. The optical flow-based VVAD is difficult to be adopted to driving scenarios due to its computational complexity. While invariant to illumination changes, Chaos theory based VVAD method is sensitive to motion translations caused by driver's head movements. The proposed Local Variance Histogram (LVH) is robust to the pixel intensity changes from both illumination change and translation change. Hence, for improved performance in environmental changes, we adopt the novel threshold estimation using total variance change. In the experimental results, the proposed VVAD algorithm achieves robustness in various driving situations.
Acoustic Analysis of a Jing Based on Drive Point and Blow Strength
Cho, Sangjin ;
The Journal of the Acoustical Society of Korea, volume 34, issue 4, 2015, Pages 328~334
DOI : 10.7776/ASK.2015.34.4.328
This paper describes an acoustic analysis of a Jing, Korean percussion instrument, according to different drive point and blow strength, and this analysis is focused on the softening and beat phenomena. Three kinds of blow strength (very strong, strong, and weak) and three locations of drive point (center, up, and right) are applied, and the spectrogram function built in Matlab is utilized to analyzing the softening and beat of target sounds. The stronger blow you drive to the center of the Jing, the more clearly softening is observed. Frequency shifting is increased proportionally to the blow strength and frequency and it is stand out on the harmonics in contrast with that of other partials. Beat of the Jing can be classified into the early beat and late beat. The beats by the outside driven Jing are distributed in wider frequency band than the beats by the center driven Jing. In addition, it is observed that the early beat is affected by few specific partials developed around harmonics for the center driven Jing.