• The Journal of the Acoustical Society of Korea
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• v.28 no.3
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• pp.260-267
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• 2009

It is very difficult to form a desired complex sound field at a designated region precisely as an application of acoustic arrays, which is one of important objects of array systems. To solve the problem, a filter design method was suggested, which employed the concept of an inverse method using the acoustical holography based on the boundary element method. In the acoustical holography used for the source identification, the measured field data are employed to reconstruct the vibro-acoustic parameters on the source surface. In the analogous problem of source array design, the desired field data at some specific points in the sound field was set as constraints and the volume velocity at the surface points of the source plane became the source signal to satisfy the desired sound field. In the filter design, the constraints for the desired sound field are set, first. The array source and given space are modelled by the boundary elements. Then, the desired source parameters are inversely calculated in a way similar to the holographic source identification method. As a test example, a target field comprised of a quiet region and a plane wave propagation region was simultaneously realized by using the array with 16 loudspeakers.

• ETRI Journal
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• v.32 no.6
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• pp.837-842
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• 2010

This paper proposes robust source localization methods for estimating the azimuth angle, elevation angle, velocity, and range using a low-complexity planar antenna array in impulsive non-Gaussian noise environments. The proposed robust source localization methods for wireless communication applications are based on nonlinear M-estimation provided from Huber and Hampel. Simulation results show the robustness performance of the proposed robust methods in impulsive non-Gaussian noise.

• Journal of Satellite, Information and Communications
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• v.11 no.3
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• pp.80-85
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• 2016

In this paper, by comparatively analyzing horn type speaker and line array type speaker developed based on line sound source theory and point sound source theory, we research whether theory is adaptable or not in real. Academically, point sound source is attenuated as much as 6dB in accordance with double distance and line sound source is attenuated as much as 3dB in accordance with double distance. Line array speaker system developed based on line sound source is analyzed by theory of line sound source about occurring small sound pressure attenuation and it is propose of research that array composition of right speaker is selected in accordance with use purpose and environment. For this purpose, we analyze theory of point sound source and line sound source. we analyze parameter value by simulating designed horn type speaker and line array speaker based on theory.

• Journal of KSNVE
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• v.6 no.6
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• pp.835-842
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• 1996

To identify the locations and strengths of acoustic sources, one may use a microphone line array. Apparent advantage of the source identification method utilizing a line array is that it requires less measurement points than intensity method and holography. This method is based on the information of magnitude and phase difference between pressure signals at each microphone. Since those differences are dependent on the source model, we have to assume them such as plane, monopole, etc. In this paper the conventional source identification methods such as beamforming method and MUSIC method are briefly reviewed by modeling a source as plane and spherical wave, then a modified method is introduced. This can be applied to sound field which may by either coherent or incoherent. Typical simulations and experiment are performed to confirm this identification method.

• The Journal of the Acoustical Society of Korea
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• v.22 no.2E
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• pp.78-86
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• 2003

We analyzed the measured acoustic field to explore the characteristics of a horizontal coherence in shallow water. Signal spatial coherence data were obtained in the continental shelf off the east coast of Korea using a horizontal line array. The array was deployed on the bottom of 130 m water depth and a sound source was towed at 26 m depth in the source-receiver ranges of 1-13 ㎞. The source transmitted 200 ㎐ pure tone. Topography and temperature profiles along the source track were measured to investigate the relationship between the horizontal coherence and environment variations. The beam bearing disturbance and array signal gain degradation is examined as parameters of horizontal coherence. The results show that the bearing disturbance is about ± 8° and seems to be affected by temporal variations of temperature caused by internal waves. The array signal gains show degradation more than 5㏈ by the temporal and spatial variations of temperature and by the down-sloped topography.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.69-76
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• 2020

The sound signal radiated from an underwater source is received by the hydrophone of the system, including multi-path time-delay and multi-path signal by sea surface and bottom reflection. The system using a time-delay between received signals for the source localization shows performance degradation due to incoherence by the multi-path propagation environment and the disturbance of a marine environment. Various types of array and signal processing have been used for robust source range and bearing estimation in this environment. In this paper, we use a line array composed of doublet array and an estimated time-delay correction method for robust localization performance in a multi-path propagation environment. Three doublet arrays are located on the same line, and the time-delay between signals received on each doublet array is estimated in a two-step procedure. The estimated time-delay value is obtained by the cross-correlation function and corrected by the interaction formula between the center-frequency of received signal and the geometry of the array with respect to aperture. By this proposed procedure, the range and bearing of source from array were calculated. In order to confirm the validity of the proposed method and array, we simulated localization and estimation using the Monte-Carlo method.

• Journal of Information Processing Systems
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• v.13 no.1
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• pp.83-94
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• 2017

Near-field source localization algorithms are very sensitive to sensor gain/phase response errors, and so it is important to calibrate the errors. We took into consideration the uniform linear array and are proposing a blind calibration algorithm that can estimate the directions-of-arrival and range parameters of incident signals and sensor gain/phase responses jointly, without the need for any reference source. They are estimated separately by using an iterative approach, but without the need for good initial guesses. The ambiguities in the estimations of 2-D electric angles and sensor gain/phase responses are also analyzed in this paper. We show that the ambiguities can be remedied by assuming that two sensor phase responses of the array have been previously calibrated. The behavior of the proposed method is illustrated through simulation experiments. The simulation results show that the convergent rate is fast and that the convergent precision is high.

• Current Optics and Photonics
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• v.5 no.5
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• pp.506-513
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• 2021

An arrayed diffractive optical element design for the beam-shaping of a multi-array light source is proposed. This is an essential device for recent optical security and face recognition applications. In practice, we devise a DC noise reduction technique featuring high fabrication error tolerance regarding the multi-array light source diffractive optical elements, as a necessary part of the proposed design method. The spherical diverging illumination leads to DC-conjugate noise spreading. The main idea is tested experimentally, and the multi-array light source diffraction pattern is investigated numerically.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.99-104
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• 2015

In this study, it has been initiated to investigate the specific abnormal vibration signal that has been captured in the power equipment. Array Microphone can be used in order to detect the direction and the position of the noise source. It is possible to track the abnormal mechanical noise in the power plant by utilizing the program and the microphone array system developed from this research. Array microphone system can be operated as a constant monitoring system.

• Transactions on Electrical and Electronic Materials
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• v.7 no.4
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• pp.180-183
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• 2006

We report for the first time two-bit operational characteristics of a high-density NOR-type polysilicon-oxide-nitride-oxide-silicon (SONOS) array with common source line (CSL). An undesired disturbance, especially drain disturbance, in the NOR array with CSL comes from the two-bit-per-cell operation. To solve this problem, we propose an efficient bulk-biased programming technique. In this technique, a bulk bias is additionally applied to the substrate of memory cell for decreasing the electric field between nitride layer and drain region. The proposed programming technique shows free of drain disturbance characteristics. As a result, we have accomplished reliable two-bit SONOS array by employing the proposed programming technique.