• 한국수산과학회지
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• 제37권5호
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• pp.433-439
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• 2004

The movement range and diurnal behavior of red seabream (Chrysophrys major) tagged by the ultrasonic pinger externally were measured by acoustic telemetry techniques in the marine ranch of Tongyeong on 20 March to 30 October, 2003. The movement of fishes was monitored with the radio-acoustic linked positioning (RAP) buoy system and VR2 receivers. The test fishes showed behavior. pattern going to deep waters and returning to shallow waters. They moved gradually to deep waters as time goes by. They had a tendency to move wider range in night-time than day-time. It was found that the test fishes rarely showed a significant response to the artificial reefs.

• Journal of Biosystems Engineering
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• 제30권1호
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• pp.38-44
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• 2005

In this study, the acoustic response technique was applied to evaluate the maturity of melon nondestructively. The acoustic response signals through melon were obtained by microphone and signal conditioner with the lapse of days after fruit set. The acoustic parameters such as resonant frequencies and the spectrum energy ratio were analyzed. To investigate the relation between acoustic parameters and firmness of melon, the compression test was performed. Three resonant frequencies representing f1, f2 and f3 were 150 to 250 Hz, 300 to 400 Hz, and 450 to 550 Hz, respectively. The resonant frequencies were shifted to the lower frequencies and the magnitude of spectrum decreased as the maturity of melon increased. Some significant correlations were found between melon firmness and the spectrum energy ratio in some frequency ranges. It is possible to estimate the maturity of melon by acoustic response technique.

• 대한의용생체공학회:의공학회지
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• 제27권5호
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• pp.229-236
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• 2006

The acoustic field analysis method is the superior calibration method for rectifying the ultrasonic probe sensitivity. This method also can be applied to evaluate the probe performance in clinical fields without numerical analysis and precise measurements. In this paper, we propose the method of acoustic field pattern analysis with probe channel division for the evaluation of diagnostic ultrasound probe characterization. In order to verify our purpose, we performed a set of experiments. We measured the acoustic-field pattern of the three inferiority probes by channel division to evaluate an acoustic field distribution and impulse response characteristics. By comparing the results of acoustic field measurement method with that of conventional method such as impulse response and live image test for linear array probes, it is demonstrated that the ultrasound field measurement method is more effective then conventional method in detection of defective elements.

• 항공우주시스템공학회지
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• 제15권4호
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• pp.40-46
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• 2021

At launch, satellites are exposed to various types of structural loads, such as quasi-static loads, sinusoidal vibrations, acoustic/random vibrations, and shocks. The launch environment test is aimed at verifying the structural stability of the test object against the launch environment. Various types of launch environments are simulated by simple vibration, acoustic, and shock tests considering possible test conditions in ground. However, the difference between the launch environment and the test environment is one of the causes of excessive testing. To prevent overtesting, a notching technique that adjusts the frequency range and the input load considering the design load is applied. For notching, specific procedures are established considering the satellite development concept, selected launch vehicle, higher system requirements, and test target level. In this study, the notching method, established procedure, and development of a notching toolkit for efficient testing are described.

• 한국군사과학기술학회지
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• 제21권4호
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• pp.422-428
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• 2018

Increase in use of lightweight structures, coupled with the increased acoustic loads resulting from larger and longer range guided missiles, has made missile more susceptible to failures caused by acoustic loads. Thus, accurate prediction of acoustic environment and the response is becoming ever more important for mission success. In this paper, the acoustic response of a sandwich composite skin structure to diffuse acoustic excitation is predicted over a broad frequency range. For the low frequency acoustic analysis, coupled FE-BEM method is used where the structure is modeled using FEM and the interior and exterior fluid is modeled using BEM. For the high frequency region, statistical energy analysis is applied. The predicted acoustic level inside the structure is compared with the result from acoustic test conducted in reverberation chamber, which shows very good agreement.

• 대한조선학회논문집
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• 제56권1호
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• pp.94-101
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• 2019

Underwater acoustic power should be measured in a free field, but it is not easy to implement. In practice, the measurement could be performed in a reverberant field such as a water-filled steel tank and concrete tank. In this case, the structure and the acoustic field are strongly or weakly coupled according to material properties of the steel and water. So, characteristics of the water tank must be investigated in order to get the accurate underwater acoustic power. In detail, modal frequencies, mode shapes of the structure and frequency response functions of the acoustic field could represent the characteristics of the reverberant water tank. In this paper, the structure-acoustic coupling has been investigated on a reverberant water tank numerically and experimentally. The finite element analysis has been carried out to estimate the structural and acoustical modal parameters under the dry and water-filled conditions, respectively. In order to investigate the structure-acoustic coupling effect, the numerical analysis has been performed according to the structure stiffness change of the water tank. The acoustic frequency response functions were compared with the numerical analysis and acoustic exciting test. From the results, the structural modal frequencies of the water-filled condition have been decreased compared to those of the dry condition in the low frequency range. The acoustic frequency response functions under the coupled boundary conditions showed different patterns from those under the ideal boundary conditions such as the pressure release and rigid boundary condition, respectively.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2008년도 공동학술대회
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• pp.41-46
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• 2008

국가하천을 대상으로 정밀외관조사에 의해 선정된20개 배수통문에 대하여 지표 물리탐사법외에 수리학적인 원리를 이용한 연통시험이나 초음파주사검층과 같은 공내시험법을 적용하여 배면의 공동상태를 보다 정확하게 파악하고자 하였다. 타음조사나 GPR 탐사, 3차원 전기비저항탐사 및 초음파주사검층은 일부 성공적인 결과를 얻을 수 있었으나 현장특성에 따라 적용이 용이하지 않은 경우가 발생하였다. 반면 연통시험의 경우에는 통문하부 공동의 유무 및 연통상태를 성공적으로 감지할 수 있었다. 그러나 연통시험은 공동의 규모나 형태에 대한 정량적인 정보를 제공하는데 근본적인 한계를 가지고 있으므로 보다 정확한 조사를 위해서는 현장특성에 맞는 다양한 조사법이 적용되어 종합적인 해석이 이루어야져야 할 것이다.

• 한국음향학회지
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• 제18권5호
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• pp.63-67
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• 1999

최근 들어 실내음향 특성의 측정과 평가를 위해 백색잡음을 이용한 잔향시간 측정법 대신에 임펄스응답을 이용한 측정법이 널리 이용되고 있다. 이 방법은 재현성이 우수하고 다양한 실내음향 특성치들을 한꺼번에 산출할 수 있어 전통적인 잔향시간 측정법에 비해 여러 가지 장점을 가지고 있다. 본 연구에서는 MLS(Maximum Length Sequence) 신호를 이용하여 실내에서의 임펄스 응답을 측정하고 이를 후처리(post-processing) 하여 잔향시간(EDT, RT), 명료도 지수(C50, C80, D, U50, U80, AI), 음의 크기 지수(G) 등, 주로 실의 음성음향 성능을 측정하는 시스템을 구축하였다. 본 연구에서는 측정시스템과 후처리 프로그램의 구성, 몇몇 실내공간에 대한 시험 측정의 결과 및 고찰 등에 대해 소개하고자 한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1995년도 춘계학술대회논문집; 전남대학교, 19 May 1995
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• pp.196-201
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• 1995

The broadband and discrete sources of sound in small cooling fans of propeller type and centrifugal type were investigated to understand the turbulent vortex structures from many bladed fans using ANSI test plenum for small air-moving devices (AMDs). The noise measurement method uses the plenum as a test apparatus to determine the acoustic source spectral density function at each operating conditions similar to real engineering applications based on acoustic similarity laws. The characteristics of fans including the head rise vs. volumetric flow rate performance were measured using a performance test facility. The sound power spectrum is decomposed into two non-dimensional functions: an acoustic source spectral distribution function F(St,.phi.) and an acoustic system response function G(He,.phi.) where St, He, and .phi. are the Strouhal number, the Helmholtz number, and the volumetric flow rate coefficient, respectively. The autospectra of radiated noise measurements for the fan operating at several volumetric flow rates,.phi., are analyzed using acoustical similarity. The rotating stall in the small propeller fan with a bell-mouth guided is mainly due to a leading edge separation. It creates a blockage in the passage and the reduction in the flow rate. The sound power levels with respect to the rotational speeds were measured to reveal the mechanisms of stall and/or surge for different loading conditions and geometries, for example, fans installed with a impinging plate. Lee and Meecham (1993) studied the effect of the large-scale motions like impinging normally on a flat plate using Large-Eddy Simulation(LES) and Lighthill's analogy.[ASME Winter Annual Meeting 1993, 93-WA/NCA-22]. The dipole and quadrupole sources in the fans tested are shown closely related to the vortex structures involved using cross-correlations of the hot-wire and microphone signals.

• 대한기관식도과학회지
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• 제7권2호
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• pp.161-167
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• 2001

Background and Objectives： Total laryngectomy is often required for advanced cases. But this operation induced the many inconvenience of basic daily life. Early diagnosis of laryngeal cancer is very important to prevent from this disastrous condition. In this point of view, mass screening test for early detection of laryngeal cancer is necessary. Screening test using voice has many advantages such as simple, less interventional. Voice collection by Automatic Response System(ARS) is comfortable and easy to got acoustic sample. Thus author tried to got the acoustic parameters which can differentiate normal, benign. and malignant laryngeal diseases and also checked the availability of parameters on neural network system. Materials and Methods: Author has evaluated the voice from 17 laryngeal cancer patients and 45 benign laryngeal disease patients who visited at Department of Otolaryngology, Pusan National University Hospital from May 1998 to April 2001, and 15 normal control. Author chose the sir Parameters (Jitt. vFo, Shim, vAm, NHR, SPI) that was thought to be related with voice collected by ARS among thirty-three parameters analysed by a Multi-Dimensional Voice Program (MDVP). Two-step neural network was used for the availability of six parameters. Results: The detection rate of normal voice by ARS voice analysis is 78.5% and detection rate of abnormal voice was 97.1 o/o. Among abnormal voice, the detection rate of benign laryngeal diseases and laryngeal cancers were 82.4 o/o, 70.6% respectively. Conclusion: Author concluded that six parameters and Matlab based neural network software may be effective in development of acoustic screening system for laryngeal cancer and further study should be necessary for development of new acoustic parameters.