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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Journal of the Acoustical Society of Korea
Journal Basic Information
Journal DOI :
The Acoustical Society of Korea
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Volume & Issues
Volume 35, Issue 4 - Jul 2016
Volume 35, Issue 3 - May 2016
Volume 35, Issue 2 - Mar 2016
Volume 35, Issue 1 - Jan 2016
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Algorithm and experimental verification of underwater acoustic communication based on passive time reversal mirror in multiuser environment
Eom, Min-Jeong ; Oh, Sehyun ; Kim, J.S. ; Kim, Sea-Moon ;
The Journal of the Acoustical Society of Korea, volume 35, issue 3, 2016, Pages 167~174
DOI : 10.7776/ASK.2016.35.3.167
Underwater communication is difficult to increase the communication capacity because the carrier frequency is lower than that of radio communications on land. This is limited to the bandwidth of the signal under the influence of the characteristics of an ocean medium. As the high transmission speed and large transmission capacity have become necessary in the limited frequency range, the studies on MIMO (Multiple Input Multiple Output) communication have been actively carried out. The performance of the MIMO communication is lower than that of the SIMO (Single Input Multiple Output) communication because cross-talk occurs due to multiusers along with inter symbol interference resulting from the channel characteristics such as delay spread and doppler spread. Although the adaptive equalizer considering multi-channels is used to mitigate the influence of the cross-talk, the algorithm is normally complicated. In this paper, time reversal mirror technique with the characteristic of a self-equalization will be applied to simplify the compensation algorithm and relieve the cross-talk in order to improve the communication performance when the signal transmitted from two channels is received over interference on one channel in the same time. In addition, the performance of the MIMO communication based on the time reversal mirror is verified using data from the SAVEX15(Shallow-water Acoustic Variability Experiment 2015) conducted at the northern area of East China Sea in May 2015.
Fabrication of a PMN-PZT needle hydrophone for photoacoustic imaging
Fan, Xiaofeng ; Cao, Yonggang ; Ha, Kanglyeol ; Kim, Moojoon ; Kang, Hyun Wook ; Oh, Junghwan ;
The Journal of the Acoustical Society of Korea, volume 35, issue 3, 2016, Pages 175~182
DOI : 10.7776/ASK.2016.35.3.175
For application to several MHz photoacoustic imaging systems, a needle hydrophone was designed and fabricated by using PMN-PZT piezoelectric single crystal, and its characteristics were evaluated through comparison with a commercial PVDF(Polybinylidene Fluoride) hydrophone of which receiving sensitivity is known. The simulation using the KLM model results show that the peak receiving impulse response for
terminating impedance of the fabricated hydrophone is -261.6 dB re
and the frequency response is relatively flat over 2 ~ 12 MHz with fluctuation less than 5 dB. The measurement results using tone burst signals also show that it has higher (ave. 10.9 dB) sensitivity than the commercial hydrophone in 2 ~ 8 MHz, and the receiving sensitivity of
was measured for the fabricated hydrophone. In addition, it is known that the photoacoustic signals and the image of a hair obtained by a mechanical scanned photoacoustic imaging system with the fabricated hydrophone were bigger and better than those obtained with the commercial hydrophone.
An integrated development methodology of low noise accessory drive system in internal combustion engines
Park, Keychun ; Kong, Jinhyung ; Lee, Byunghyun ;
The Journal of the Acoustical Society of Korea, volume 35, issue 3, 2016, Pages 183~191
DOI : 10.7776/ASK.2016.35.3.183
A systematic development process for the low noise FEAD (Front End Accessory Drive) system is presented by combining CAE (Computer Aided Engineering) and the experimental rig test. In the estimation of the belt drive noise, two main difficulties arise from the high non-linearity due to the stick-slip contacts on the interfaces of the belt and pulleys, and the interaction of the belt drive system with the powertrain rotational parts. In this work, a recently developed analysis method of the belt drive has been employed considering powertrain rotational dynamics. As results, it shows good correlation with the vehicle tests in various operational modes. The established model has been employed to validate the new design improving the stick-slip noise of the problematic FEAD system. Furthermore, the best proposal of FEAD system in terms of functionality [NVH (Noise, Vibration and Harshness), fuel economy, cost. etc.] has been suggested in the concept design stage of new engine through this presented methodology.
Distribution of vibration signals according to operating conditions of wind turbine
Shin, Sung-Hwan ; Kim, SangRyul ; Seo, Yun-Ho ;
The Journal of the Acoustical Society of Korea, volume 35, issue 3, 2016, Pages 192~201
DOI : 10.7776/ASK.2016.35.3.192
Condition Monitoring System (CMS) has been used to detect unexpected faults of wind turbine caused by the abrupt change of circumstances or the aging of its mechanical part. In fact, it is a very hard work to do regular inspection for its maintenance because wind turbine is located on the mountaintop or sea. The purpose of this study is to find out distribution patterns of vibration signals measured from the main mechanical parts of wind turbine according to its operation condition. To this end, acceleration signals of main bearing, gearbox, generator, wind speed, rotational speed, etc were measured through the long period more than 2 years and trend analyses on each signal were conducted as a function of the rotational speed. In addition, correlation analysis among the signals was done to grasp the relation between mechanical parts. As a result, the vibrations were dependent on the rotational speed of main shaft and whether power was generated or not, and their distributions at a specific rotational speed could be approximated to Weibull distribution. It was also investigated that the vibration at main bearing was correlated with vibration at gearbox each other, whereas vibration at generator should be dealt with individually because of generating mechanism. These results can be used for improving performance of CMS that early detects the mechanical abnormality of wind turbine.
Factors affecting recognition of successive impulsive noise
Lee, Jae-Won ; Shin, Sung-Hwan ;
The Journal of the Acoustical Society of Korea, volume 35, issue 3, 2016, Pages 202~207
DOI : 10.7776/ASK.2016.35.3.202
Most of noises from cars or home appliances accompany successive impulsive noise due to repeated operation. A human auditory system is able to perceive the successive impulsive noise as either a set of independent noise or amplitude modulated noise according to its occurrence period. This study is to identify main influence factors on understanding of impulsive characteristics and find most appropriate sound quality metrics to express the successive impulsive noise. To do this, the successive impulsive noises were designed and utilized to perform a listening test for identifying conditions where successive impulsive noise can be recognized to have impulsive characteristics. These results were analyzed with sound quality metrics such as loudness, fluctuation strength, and roughness in order to compare the subjective results with the objective results. Consequently, the results revealed that the successive impulsive noise exhibits impulsive characteristics when its occurrence frequency is less than 50 Hz. It was also observed that roughness and fluctuation strength results are not applicable to express the successive impulsive noise because they heavily depend on the amplitude modulation characteristics. On the other hand, loudness results are considered to be useful as an evaluation factor of the successive impulsive noise through the use of loudness limen because it does not depend on the amplitude modulation characteristics.
Development of the combustion noise index and control algorithm through signal processing of in-cylinder pressure for a diesel engine
Jin, Jaemin ; Lee, Dongchul ; Jung, Insoo ;
The Journal of the Acoustical Society of Korea, volume 35, issue 3, 2016, Pages 208~215
DOI : 10.7776/ASK.2016.35.3.208
To control and improve a combustion behavior of an engine, various studies for the in-cylinder pressure have been consistently carried out. In this paper, the level of the combustion noise for a diesel engine is estimated from the in-cylinder pressure and defined as the combustion noise index. The combustion noise index is calculated from the FFT(Fast Fourier Transform) of the in-cylinder pressure and its validity is verified. The control system based on the combustion noise index is developed and implemented in a vehicle. A number of injection parameters are controlled to meet the desired combustion noise index, and the combustion noise of a vehicle is improved up to 4.0 dB(A) in the specified frequency band.
Performance improvement of a quiet zone using multichannel real-time active noise control system
Mu, Xiangbin ; Ko, JinSeok ; Rheem, JaeYeol ;
The Journal of the Acoustical Society of Korea, volume 35, issue 3, 2016, Pages 216~222
DOI : 10.7776/ASK.2016.35.3.216
Generation of a quiet zone in noisy environment is undoubtedly of considerable realistic significance. This paper describes development and implementation of a multichannel real-time active noise control (ANC) system for 3 dimensional noisy environment to enhance the quiet zone performance in terms of size and noise cancellation gain. The proposed ANC system employes a multichannel delay-compensated filtered-X least mean square (FXLMS) algorithm; its real-time implementation is designed in TMS320C6713 digital signal processor (DSP) board. The system is evaluated for cancelling various tonal frequency noises in the range from 100 to 500 Hz, and the performance is then illustrated by measuring the quiet zone in terms of sound pressure level (SPL) attenuation. Experiment results show that a quiet zone of quiet with satisfactory size and maximum 24 dB noise attenuation is successfully generated.
An analyses of the noise reduction effect of vegetation noise barrier using scaled model experiments
Haan, Chan-Hoon ; Hong, Seong-Shin ;
The Journal of the Acoustical Society of Korea, volume 35, issue 3, 2016, Pages 223~233
DOI : 10.7776/ASK.2016.35.3.223
Design of a vegetation type sound barrier was presented as a noise barrier on the boundary of neighborhood facilities including schools, and apartments. The suggested noise barrier is made of unit blocks that are to be formed by stacking over the wall structure containing the plant and soils in the blocks. The advantage of the vegetation noise barrier is to acquire not only sound absorptive effects of plants and soils, but also sound diffusive effect caused by the irregular surface of the barrier which could eventually mitigate the noise. First, the optimum size of the units to obtain the highest noise reduction was investigated using 1/10 scaled model experiment, and sound attenuation experiments were carried out using a 1/2 mock-up model which is 2 m high and 5 m long. Total 1,137 unit blocks were made of synthetic woods with the size of
. These unit blocks were installed on the both side of the 1/2 mock-up steel framed noise barrier. As a result, it was revealed that the block typed vegetation noise barrier has 7 dB higher insertion loss in comparison with the general plane noise barrier. Also, it was found that the appropriate size of unit blocks is
which has large effect of sound insertion loss.
On-line noise coherence estimation algorithm for binaural speech enhancement system
Ji, Youna ; Baek, Yong-hyun ; Park, Young-cheol ;
The Journal of the Acoustical Society of Korea, volume 35, issue 3, 2016, Pages 234~242
DOI : 10.7776/ASK.2016.35.3.234
In this paper, an on-line noise coherence estimation algorithm for binaural speech enhancement system is proposed. A number of noise Power Spectral Density (PSD) estimation algorithms based on the noise coherence between two microphones have been proposed to improve the speech enhancement performance. In the conventional algorithms, the noise coherence was characterized using a real-valued analytic model. However, unlike the analytic model, the noise coherence between the two microphones is time-varying in real environments. Thus, in this paper, the noise coherence is updated in accordance with the variation of the acoustic environment to track the realistic noise coherence. The noise coherence can be updated only during the absence of speech, and the simulation results demonstrate the superiority of the proposed algorithm over the conventional algorithms based on the analytic model.