• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.11a
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• pp.56-59
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• 2015

본 논문에서는 스테레오 오디오 신호를 이용하여 음원을 분리하는 ADRess 알고리즘을 기반으로, 추정된 음원 방위각에 대한 신호 강도비를 이용하여 분리음원을 생성하는 새로운 분리음원 합성 기법을 제안한다. 입력된 스테레오 채널 신호 간 강도 차(IID) 특성을 이용하여 신호 분석 프레임별로 개선된 신호 강도비 함수에 따른 frequency-azimuth 평면을 구성하고, 이를 통해 추정된 방위각에 상응하는 신호 강도비로 표현되는 확률밀도함수를 좌/우 신호 중 하나의 주 입력 신호에 취함으로써 분리음원을 합성한다. 제안된 기법의 성능을 검증하기 위하여 SASSEC 에서 제공하는 테스트 음원 및 객관적 평가 지표를 이용하여 측정한 결과, 기존 ADRess 알고리즘에서 제시된 방법에 비해 개선된 품질의 분리음원을 합성하는 것으로 평가되었다.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.12
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• pp.191-196
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• 2013

In this paper, the interaural intensity difference (IID)-based sounr source separation method in closely spaced stereo omnidirectional microphones is proposed. First, in order to improve the channel separability, a minimum variance distortionless response (MVDR) beamformer is employed to increase the intensity difference between stereo channels. After that, IID-based sound source separation method is applied. In order to evaluate the performance of the proposed method, source-to-distortion ratio (SDR), source-to-interference ratio (SIR), and sources-to-artifacts ratio (SAR), which are defined as objective evaluation criteria in stereo audio source separation evaluation campaign (SASSEC), are measured. As a result, it was shown from the objective evaluation that the proposed method outperforms a sound source separation method without applying a beamformer.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.11
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• pp.1020-1026
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• 2013

An accurate railway environmental noise prediction model is required to make the proper solution of the railway noise problems. In this paper, an engineering model for predicting the noise of conventional passenger cars is presented considering the acoustic source strength in octave-band frequencies and the propagation over grounds with varying surface properties. Since the formation of a train can be variable, the source strength of each locomotive and passenger car was estimated by measuring the pass-by noise and analysing the wheel-rail rolling noise. Some validation cases show on the average small differences between the predictions of the present model and the measurement results.

• The Journal of the Acoustical Society of Korea
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• v.43 no.1
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• pp.138-144
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• 2024

This paper presents a bistatic to monostatic conversion technique to analyze the bistatic target strength of submarines. The technique involves determining the transmission path length of acoustic waves, which are emitted from a source, scattered off an underwater target, and eventually received by a receiver. By generating a corresponding virtual scattering surface, this method effectively transforms the target strength analysis problem from bistatic to monostatic. The converted monostatic target strength problem can be assessed using a well-established monostatic numerical methods. The bistatic target strength analysis for Benchmark Target Strength Simulation (BeTTSi), a widely used target strength model were performed. The results were compared with those calculated by boundary element methods and Kirchhoff approximation, and confirmed the validity and the practical applicability of the proposed analysis technique for evaluating submarine target strength.

• The Journal of the Acoustical Society of Korea
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• v.40 no.4
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• pp.330-336
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• 2021

In bistatic sonar operation, the scattering strength of a sonar target is characterized by the probe signal frequency, the aspect angle and the bistatic angle. Therefore, the target detection and identification performance of the bistatic sonar may vary depending on how the positions of the target, sound source, and receiver are changed during sonar operation. In this study, it was evaluated which variable is advantageous to change by comparing the target identification performance between the case of changing the aspect angle and the case of changing the bistatic angle during the operation. A scenario of identifying a hollow sphere and a cylinder was assumed, and performance was compared by classifying two targets with a support vector machine and comparing their accuracy using a finite element method-based acoustic scattering simulation. As a result of comparison, using the scattering strength defined by the frequency and the bistatic angle with the aspect angle fixed showed superior average classification accuracy. It means that moving the receiver to change the bistatic angle is more effective than moving the sound source to change the aspect angle for target identification.

• Journal of the Korea Concrete Institute
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• v.22 no.1
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• pp.113-122
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• 2010

Corrosion of prestressing tendons and wire fractures in grouted post-tensioned prestressed concrete bridges have been considered as a serious safety problem. In bridge evaluation the condition of prestressing tendons should be inspected, and if corroded tendons are found, the loss of tendon area should be included when we calculate the ultimate strength. In the previous study, it was evaluated that continuous acoustic monitoring techniques could be considered as a reliable non-destructive method for detecting wire fractures of fully grouted post-tensioned prestressing tendons. In the present study, an experimental test was performed for detecting wire fractures of post-tensioned prestressing tendons which are prestressed lower than current design level. A 10 m prestressed concrete beam was fabricated, which included two tendons prestressed 66 percentage and 40 percentage of tensile strength, respectively. The corrosion of two tendons was induced by an accelerated corrosion equipment and the test beam was monitored by using seven acoustic sensors and a continuous acoustic monitoring system. From each prestressing tendon, two acoustic signals of wire fractures were successfully detected and source locations were estimated within 20 mm error. Based on the test results, it is considered that continuous acoustic monitoring techniques can be applied to detect low-prestressed wire fracture in fully grouted post-tensioned prestressed concrete beams.

• Korean Journal of Ecology and Environment
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• v.40 no.2
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• pp.244-253
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• 2007

In this study, mortality, body wet weight, health assessment, and short-term behavioral mode were observed to determine the effects of ultrasound on the ecological response of the carp Cyprinus carpio. Mortality in the treatments was less than 5% during ultrasound exposure (31 dB re 1 ${\mu}Pa$, $14{\sim}15$ kHz) and there were no significant differences among the replicates (P>0.05). The treatments, based on mean wet weight, exhibited greater effect than the controls, but the magnitude of the differences was not large. Skins and tail fins of some test animals exposed to the controls and intensive treatment groups had light injury such as hemorrhaging, whereas, damages in other organs such as eyes, other fins, parasites, thymus, and gills were not observed (P>0.05). Sudden stimuli in low intensity at a short distance caused a directional avoidance of the fish from the sound. However, the carp exposed to ultrasound at the large scale field was not observed clear behavior changes. Overall results suggest that fish exposed to the low-intensity ultrasound had no serious stress during the tests.