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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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Design and Fabrication of Multi-mode Wideband Tonpilz Transducers
Kim, Jinwook ; Kim, Hoeyong ; Roh, Yongrae ;
The Journal of the Acoustical Society of Korea, volume 32, issue 3, 2013, Pages 191~198
DOI : 10.7776/ASK.2013.32.3.191
In this paper, we designed a wideband Tonpilz transducer, and verified the validity of the design through experiments. The wide frequency bandwidth was achieved by coupling the fundamental longitudinal mode of the transducer with a flapping mode of the head mass. Structure of the Tonpilz transducer was optimized by means of the finite element method and genetic algorithm to achieve the widest fractional bandwidth under design constraints. The optimized structure showed a far wider -6 dB fractional bandwidth of transmitting responses than that of single mode transducers. For verification of the design result, we manufactured a transducer prototype of the designed structure and characterized its performance, which showed good agreement with the design results.
Design and Fabrication of a 1.75D Ultrasonic Transducer
Lee, Wonseok ; Roh, Yongrae ;
The Journal of the Acoustical Society of Korea, volume 32, issue 3, 2013, Pages 199~207
DOI : 10.7776/ASK.2013.32.3.199
In this paper, a
channel 1.75D ultrasonic transducer made of piezoelectric single crystals was designed, fabricated, and evaluated. First, a structure of the transducer was selected to be suitable for wiring on a planar array, and components were fabricated to correspond to the structure. Detailed structure of the transducer was designed through finite element analyses. As main performance factors, the crosstalk between neighboring elements was reduced through the control of kerf width and material, and desired frequency bandwidth of the transducer was achieved by designing the optimal thicknesses of the piezoelectric single crystal and matching layers. An experimental prototype of the transducer was fabricated following the design, and its performance was measured. Then the experimental results were compared with those of the finite element analysis, which led to the evaluation of the transducer developed in this work.
Responses and Stresses of Structural Vibration of a Camshaft
Choi, Myung-Jin ;
The Journal of the Acoustical Society of Korea, volume 32, issue 3, 2013, Pages 208~213
DOI : 10.7776/ASK.2013.32.3.208
To get vibration responses, a camshaft is modelled as an unbalanced multiple rotor bearing system. Because of complex geometry and complicated load conditions, the finite element method is used. After the finite element equation of the system is constructed, Newmark's method is used to get the vibration responses. Whirl vibration responses of a V-8 engine camshaft are estimated and compared with measured responses. After the fluctuating stresses are obtained, fatigue analysis is performed based upon the modified Goodman's equation. Stress concentration effects are considered. In the whirl vibration of camshafts, the bending effect is dominant, and the bending deformation is dependent upon the span length between the adjacent bearing journals. For high speeds, the fluctuations of excitation forces are large, and it is known that nonlinear time varying bearing coefficients should be used for analysis.
Review of Standard Sound Quality Assessment Methods for the Transmitted and Processed Sounds
Oh, Wongeun ;
The Journal of the Acoustical Society of Korea, volume 32, issue 3, 2013, Pages 214~226
DOI : 10.7776/ASK.2013.32.3.214
Assessing the quality of audio signals is an important consideration in making high quality sounds and various methods have been developed. This paper provides a general framework of sound quality and a technical overview of the international standard methods which are described in ITU-T, ITU-R, IEC and ANSI Recommendations in the speech intelligibility, speech quality, and audio quality areas. In addition, some recent findings and future works are included.
Quality Improvement of Karaoke Mode in SAOC using Cross Prediction based Vocal Estimation Method
Lee, Tung Chin ; Park, Young-Cheol ; Youn, Dae Hee ;
The Journal of the Acoustical Society of Korea, volume 32, issue 3, 2013, Pages 227~236
DOI : 10.7776/ASK.2013.32.3.227
In this paper, we present a vocal suppression algorithm that can enhance the quality of music signal coded using Spatial Audio Object Coding (SAOC) in Karaoke mode. The residual vocal component in the coded music signal is estimated by using a cross prediction method in which the music signal coded in Karaoke mode is used as the primary input and the vocal signal coded in Solo mode is used as a reference. However, the signals are extracted from the same downmix signal and highly correlated, so that the music signal can be severely damaged by the cross prediction. To prevent this, a psycho-acoustic disturbance rule is proposed, in which the level of disturbance to the reference input of the cross prediction filter is adapted according to the auditory masking property. Objective and subjective test were performed and the results confirm that the proposed algorithm offers improved quality.
A Study on Hydrophone Array Design Optimization for Cavitation Tunnel Noise Measurements
Park, Cheolsoo ; Seol, Hanshin ; Kim, Gundo ; Park, Youngha ;
The Journal of the Acoustical Society of Korea, volume 32, issue 3, 2013, Pages 237~246
DOI : 10.7776/ASK.2013.32.3.237
This paper proposes a hydrophone array design optimization technique for cavitation tunnel noise measurements. The optimization technique comprises of design parameters, an objective function and an optimization algorithm. The design parameters are defined for circular, spiral and multi-spiral arrays. The objective function is defined so as to consider the mainlobe beamwidth and the maximum sidelobe level simultaneously. A global optimization scheme is applied to the array design using very fast simulated reannealing (VFSR). After applying the optimization technique to arrays respectively, the peak sidelobe level and the mainlobe beamwidth of optimum arrays are analyzed. Finally the array patterns considering multiple reflections in the cavitation tunnel are evaluated to validate the proposed method.
Near-field Source Localization Method using Matrix Pencil
Jung, Tae-Jin ; Lee, Su-Hyoung ; Yoon, Kyung Sik ; Lee, KyunKyung ;
The Journal of the Acoustical Society of Korea, volume 32, issue 3, 2013, Pages 247~251
DOI : 10.7776/ASK.2013.32.3.247
In this paper, near-field source localization algorithm is presented using Matrix Pencil in Uniform Linear Array(ULA). Based on the centrosymmetry of the ULA, the proposed algorithm decouples the steering vectors which allow for the bearing estimation using Matrix pencil. With estimated bearing, the range estimation of each source is consequently obtained by defining 1D MUSIC spectrum. Simulation results are presented to validate the performance of the proposed algorithm.
Noise Robust Speech Recognition Based on Parallel Model Combination Adaptation Using Frequency-Variant
Choi, Sook-Nam ; Chung, Hyun-Yeol ;
The Journal of the Acoustical Society of Korea, volume 32, issue 3, 2013, Pages 252~261
DOI : 10.7776/ASK.2013.32.3.252
The common speech recognition system displays higher recognition performance in a quiet environment, while its performance declines sharply in a real environment where there are noises. To implement a speech recognizer that is robust in different speech settings, this study suggests the method of Parallel Model Combination adaptation using frequency-variant based on environment-awareness (FV-PMC), which uses variants in frequency; acquires the environmental data for speech recognition; applies it to upgrading the speech recognition model; and promotes its performance enhancement. This FV-PMC performs the speech recognition with the recognition model which is generated as followings: i) calculating the average frequency variant in advance among the readily-classified noise groups and setting it as a threshold value; ii) recalculating the frequency variant among noise groups when speech with unknown noises are input; iii) regarding the speech higher than the threshold value of the relevant group as the speech including the noise of its group; and iv) using the speech that includes this noise group. When noises were classified with the proposed FV-PMC, the average accuracy of classification was 56%, and the results from the speech recognition experiments showed the average recognition rate of Set A was 79.05%, the rate of Set B 79.43%m, and the rate of Set C 83.37% respectively. The grand mean of recognition rate was 80.62%, which demonstrates 5.69% more improved effects than the recognition rate of 74.93% of the existing Parallel Model Combination with a clear model, meaning that the proposed method is effective.
Comparative Studies of Perceiving Korean Monosyllabic Digit Words under Different Speech Compression Schemes
Lim, Dukhwan ; Won, Yookyung ;
The Journal of the Acoustical Society of Korea, volume 32, issue 3, 2013, Pages 262~268
DOI : 10.7776/ASK.2013.32.3.262
The performances of speech compression schemes appeared to be dependent on the response profiles to compressed stimuli and the features of individual languages to some extent. Although these response profiles were critical in comparing various compression outcomes, the related data were limited in number for Korean monosyllabic words. From the previous study, data from PNT (Preserving No Trait) compression was selected as a base set for comparison. In this study, the outcomes from PPT (Preserving Pitch Trait) and PTT (Preserving Time Trait) were analyzed under the same condition. Then, the properties of these three widely used representative compression schemes were quantitatively compared in normal hearing adults (N=20) for controlled Korean quintet digit sets (0 through 9). Results showed that PPT compression scheme exhibited the best perceptual performances for the Korean quintet digit sets in the final outcomes (PPT>PTT>PNT). The compression ratios of 50% performances were estimated as about 20%, 42%, and 44% for PPT, PTT, and PNT, respectively. The data indicated the influences of the salient psychoacoustic features of the three representative compressions on perceiving Korean monosyllabic digit words. This controlled procedure with monosyllabic quintet sets can evaluate efficiency and effectiveness of other compression schemes and may also contribute to diagnosing auditory processing disorders and fitting special hearing aids with compression issues.
Restoration for Speech Records Managed by the National Archives of Korea
Oh, Sejin ; Kang, Hong-Goo ;
The Journal of the Acoustical Society of Korea, volume 32, issue 3, 2013, Pages 269~278
DOI : 10.7776/ASK.2013.32.3.269
The speech recording of the National Archives of Korea contains very important traces which represent modern times of Korea. But the way to be recorded by analogue is easily contaminated as time goes by. So it has to be digitalized for management and services. Consequently, restoration method of distorted speech is needed. We propose the four classes for each distortion kind and apply restoration algorithms for the cases of speech level, stationary noise and abrupt noise. As a result, speech volume adjusts to -26 dBov for only on the speech region and SNR improves above 10dB. Especially, conventional way to remove the noise is almost impossible because we need to listen to all of them but it can be more effective by adaptation of auto restoration algorithm.
Global Soft Decision Based on Improved Speech Presence Uncertainty Tracking Method Incorporating Spectral Gradient
Kim, Jong-Woong ; Chang, Joon-Hyuk ;
The Journal of the Acoustical Society of Korea, volume 32, issue 3, 2013, Pages 279~285
DOI : 10.7776/ASK.2013.32.3.279
In this paper, we propose a novel speech enhancement method to improve the performance of the conventional global soft decision which is based on the spectral gradient method applied to the ratio of a priori speech absence and presence probability value (q). Conventional global soft decision scheme used a fixed value of q in accordance with the hypothesis assumed, but the proposed algorithm is a technique for improving the speech absence probability which is applied adaptively variable value of q according to the speech presence or absence in the previous two frames and the conditions of the spectral gradient value. Experimental results show that the proposed improved global soft decision method based on the spectral gradient method yields better results compared to the conventional global soft decision technique based on the performance criteria of the ITU-T P. 862 PESQ (Perceptual Evaluation of Speech Quality).