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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 33, Issue 6 - Nov 2014
Volume 33, Issue 5 - Sep 2014
Volume 33, Issue 4 - Jul 2014
Volume 33, Issue 3 - May 2014
Volume 33, Issue 2 - Mar 2014
Volume 33, Issue 1 - Jan 2014
Selecting the target year
Measurements of Ultrasound Attenuation Coefficient at Various Suspended Sediment Concentrations
Lee, Changil ; Choi, Jee Woong ;
The Journal of the Acoustical Society of Korea, volume 33, issue 1, 2014, Pages 1~9
DOI : 10.7776/ASK.2014.33.1.001
Coastal water including estuaries has distinctive environmental characteristics where sediments are transported and deposited by flowing river water, providing an environment in which fluid mud layers can be formed. Acoustic method is mostly used to detect or monitor the fluid mud layer. However, since sound propagating in this layer suffers severe attenuation, it is important to estimate the accurate attenuation coefficient for various concentrations of fluid mud layer for the successful use of the acoustic method. In this paper, measurement results of attenuation coefficient for 3.5, 5, and 7.5 MHz ultrasounds were presented. The measurements were made in a small-size water tank in which suspended sediment samples with various sediment concentrations were formed using kaolinite powder. The results were compared to the model predictions obtained by attenuation coefficient model in which the mean grain size (called as Mass-median-diameter, D50) was used as input parameter. There were reasonable agreements between measured attenuation coefficients and model outputs predicted using the particle range of D50
. The comparison results imply that although the suspended sediments consist of various-sized particles, sound attenuation might be greatly influenced by amount of particle with a size which has a larger attenuation than that of any particle in the suspended sediments for the frequency used.
Experimental Study on Underwater Transient Noise Generated by Water-Entry Impact
Jung, Youngcheol ; Seong, Woojae ; Lee, Keunhwa ; Kim, Hyoungrok ;
The Journal of the Acoustical Society of Korea, volume 33, issue 1, 2014, Pages 10~20
DOI : 10.7776/ASK.2014.33.1.010
To study the water-entry impact noise, on-board experiment using a small launcher firing various objects was performed in the Yellow Sea. As the launcher fires a cylindrical object from the ship vertically, generated noise is measured with a hydrophone on the starboard of Chung-hae, Marine surveyor. Three types of cylindrical objects, which have noses of flat-faced, conical, and hemisphere, were used during the experiment. The measured noise exhibits a time-dependency which can be divided into three phases: (1) initial impact phase, (2) open cavity flow phase, (3) cavity collapse and bubble oscillation phase. In most cases, the waveform of bubble oscillation phase is dominant rather than that of initial impact phase. Pinch-off time, where a cavity begins to collapse, occurs at 0.18 ~ 0.2 second and the average lasting time of bubble was 0.9 ~ 1.3 second. The energy of water-entry impact noise is focused in the frequency region lower than 100 Hz, and the generated noise is influenced by the nose shapes, object mass, and launching velocity. As a result, energy spectral density on the bubble frequency is higher in the order of flat-faced, conical, hemisphere nose, and the increase of initial energy raises the energy spectral density on the bubble frequency in the cylinder body of same shape. Finally, we compare the measurements with the simulated signals and spectrum based on the bubble explosion physics, and obtain satisfactory agreements between them.
Visualization of Temperature Elevation Due to Focused Ultrasound in Dissipative Acoustic Medium
Kim, Myoungseok ; Kim, Jungsoon ; Kim, Moojoon ; Ha, Kanglyeol ;
The Journal of the Acoustical Society of Korea, volume 33, issue 1, 2014, Pages 21~30
DOI : 10.7776/ASK.2014.33.1.021
The temperature change due to focused ultrasound in dissipative acoustic medium is very important because it provides us much information. To measure the temperature change inside of the dissipative acoustic medium non-invasively, we adopt a temperature sensitive film which has thermochromic particles with critical temperature of
. As a dissipative acoustic medium, agar layer is chosen in the study. The temperature change due to the ultrasound was measured depending on the concentration of the sugar in the agar layer. The color change on the film due to the ultrasound was investigated when the concentration of sugar was from 25% to 40%. As the result, there were rapid increases of discolored area on the film within 2~5 second after the ultrasound driving and the increasing rates decreased after the period. To compare the simulation results were also shown. However in the simulated result, the discolored areas linearly increased from start to 10 seconds. The reason of the differences between the experimental results and simulated ones is that the change of thermal conductivity and heat capacity of the medium were not considered in the simulation program.
Calibration System for Angular Vibration Using Precision Rotary Encoder
Nam, Seunghwan ; Baik, Kyungmin ; Cheung, Wan-Sup ;
The Journal of the Acoustical Society of Korea, volume 33, issue 1, 2014, Pages 31~39
DOI : 10.7776/ASK.2014.33.1.031
In this paper, two calibration methods for angular vibration pickups using a precision rotary encoder are proposed. The KRISS (Korea Research Institute of Standards and Science) primary angular vibration calibration system and the calibration procedures are briefly explained. The rotary encoder is shown to be calibrated in two methods: The one is to use the laser interferometer to calibrate the rotary encoder under test and the other is to exploit the certificate of the encoder supplied. Complex sensitivities measured from the first are shown to be less than 0.1 % difference in magnitude and
difference in phase shift in reference to those of the primary calibration system. Their expanded uncertainties were observed to be less than 0.6 % in magnitude and
in phase shift over the range of 0.4 to 200 Hz. Under the same calibration conditions, complex sensitivities evaluated by the second method are shown be 0.1 % difference in magnitude and
difference in phase shift in reference to those of the primary calibration system. Their expanded uncertainties were seen to be less than 4.8 % in magnitude and
in phase shift.
Analysis of Relative Contributions of Tonal Noise Sources in Volute Tongue Region of a Centrifugal Fan
Heo, Seung ; Kim, Daehwan ; Cheong, Cheolung ;
The Journal of the Acoustical Society of Korea, volume 33, issue 1, 2014, Pages 40~47
DOI : 10.7776/ASK.2014.33.1.040
Interaction between the unsteady flow emitted from the blade of the centrifugal fan and the volute tongue region of fan duct is known as the main noise source of the centrifugal fan. In this paper, the relative contributions of the volute tongue region of the centrifugal fan is analyzed to utilize as the foundation data of low noise design. The internal hybrid CAA (Computational Aero-Acoustics) method is used to predict noise radiated from the main noise source. This method is the noise prediction technique using CFD (Computational Fluid Dynamics), Acoustic analogy, and BEM(Boundary Element Method). The relative contributions of the centrifugal fan volute tongue region using the hybrid CAA method show that the region between the cut-off and the scroll has high contribution than the region between the cut-off and the outlet and the hub region of blade has high contribution than the shroud region of blade. These results is utilized as the important data for the development of low noise centrifugal fan.
Mitigation of Inter-Symbol Interference in Underwater Acoustic Communication Using Spatial Filter
Eom, Min-Jeong ; Park, Ji-Sung ; Ji, Yoon-Hee ; Kim, J.S. ;
The Journal of the Acoustical Society of Korea, volume 33, issue 1, 2014, Pages 48~53
DOI : 10.7776/ASK.2014.33.1.048
The underwater acoustic communication (UAC) is characterized by doubly spread channel. It is included in the time-variant doppler shift and delay-time spreads due to multiple paths. To compensate such distorted signals, various techniques including time-reversal processing, spatial diversity, phase estimator, and equalizer are being applied. In this paper, a spatial filter based on the beamforming is proposed as a method to mitigate such inter-symbol interferences that are generated in time-varying multipath channels. The proposed technique realizes coherent communications by steering the direction of the desired signals and improves the performance of UAC by increasing the signal-to-interference plus noise ratio using the array gain.
CASA Based Approach to Estimate Acoustic Transfer Function Ratios
Shin, Minkyu ; Ko, Hanseok ;
The Journal of the Acoustical Society of Korea, volume 33, issue 1, 2014, Pages 54~59
DOI : 10.7776/ASK.2014.33.1.054
Identification of RTF (Relative Transfer Function) between sensors is essential to multichannel speech enhancement system. In this paper, we present an approach for estimating the relative transfer function of speech signal. This method adapts a CASA (Computational Auditory Scene Analysis) technique to the conventional OM-LSA (Optimally-Modified Log-Spectral Amplitude) based approach. Evaluation of the proposed approach is performed under simulated stationary and nonstationary WGN (White Gaussian Noise). Experimental results confirm advantages of the proposed approach.
Concepts of Sound Control System Using Absolute Sound Level
Kyon, Doo-Heon ; Bae, Myung-Jin ;
The Journal of the Acoustical Society of Korea, volume 33, issue 1, 2014, Pages 60~67
DOI : 10.7776/ASK.2014.33.1.060
The purpose of this study is to suggest a new concept of the absolute sound level system in order to basically solve all the irrational aspects from the mastering stage to the output stage during the process of producing a sound source. Through this absolute sound level system, all the input absolute sound levels of sound sources become standardized based on 60 dB(S), and then sound source producers can implement a sound level they intend by using the differential sound level tag. Besides, by matching the output absolute sound level with the input absolute sound level, a target sound level can be implemented as a listener intends. With this system introduced, sound source producers are able to focus on the completion of a sound source itself without an unnecessary competition for sound levels, and only by inputting the differential reduction tag, they can implement a sound level balance as intended. At the same time, listeners are able to appreciate all kinds of sound sources fit for the standard of absolute s ound levels they want to listen to, without a process of trial and error, no matter what kinds of listening environments and sound systems they have.
Histogram Equalization Using Centroids of Fuzzy C-Means of Background Speakers' Utterances for Majority Voting Based Speaker Identification
Kim, Myung-Jae ; Yang, Il-Ho ; Yu, Ha-Jin ;
The Journal of the Acoustical Society of Korea, volume 33, issue 1, 2014, Pages 68~74
DOI : 10.7776/ASK.2014.33.1.068
In a previous work, we proposed a novel approach of histogram equalization using a supplement set which is composed of centroids of Fuzzy C-Means of the background utterances. The performance of the proposed method is affected by the size of the supplement set, but it is difficult to find the best size at the point of recognition. In this paper, we propose a histogram equalization using a supplement set for majority voting based speaker identification. The proposed method identifies test utterances using a majority voting on the histogram equalization methods with various sizes of supplement sets. The proposed method is compared with the conventional feature normalization methods such as CMN(Cepstral Mean Normalization), MVN(Mean and Variance Normalization), and HEQ(Histogram Equalization) and the histogram equalization method using a supplement set.
Packet Loss Concealment Algorithm Based on Robust Voice Classification in Noise Environment
Kim, Hyoung-Gook ; Ryu, Sang-Hyeon ;
The Journal of the Acoustical Society of Korea, volume 33, issue 1, 2014, Pages 75~80
DOI : 10.7776/ASK.2014.33.1.075
The quality of real-time Voice over Internet Protocol (VoIP) network is affected by network impariments such as delays, jitters, and packet loss. This paper proposes a packet loss concealment algorithm based on voice classification for enhancing VoIP speech quality. In the proposed method, arriving packets are classified by an adaptive thresholding approach based on the analysis of multiple features of short signal segments. The excellent classification results are used in the packet loss concealment. Additionally, linear prediction-based packet loss concealment delivers high voice quality by alleviating the metallic artifacts due to concealing consecutive packet loss or recovering lost packet.
A Musical Genre Classification Method Based on the Octave-Band Order Statistics
Seo, Jin Soo ;
The Journal of the Acoustical Society of Korea, volume 33, issue 1, 2014, Pages 81~86
DOI : 10.7776/ASK.2014.33.1.081
This paper presents a study on the effectiveness of using the spectral and the temporal octave-band order statistics for musical genre classification. In order to represent the relative disposition of the harmonic and non-harmonic components, we utilize the octave-band order statistics of power spectral distribution. Experiments on the widely used two music datasets were performed; the results show that the octave-band order statistics improve genre classification accuracy by 2.61 % for one dataset and 8.9 % for another dataset compared with the mel-frequency cepstral coefficients and the octave-band spectral contrast. Experimental results show that the octave-band order statistics are promising for musical genre classification.