• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.1189-1194
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• 2002

Acoustic intensity is usually estimated by the cross-spectrum of acoustic pressure at two adjacent micrphones. The cross-spectrum calculated by digital Fourier transform technique will unavoidally have leakage error since the period of signal will not be usually coincident with record length. Therefore, the acoustic intensity estimated by the conventional r]n analyzer will show distorted value. In this paper the expression of the Fourier transformed data of a harmonic signal is formulated when there is leakage error. The method to elimate the effect of leakage error from the contaminated data is also proposed. Some numerical examples show the validation of the proposed method.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.1156-1161
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• 2001

Acoustic intensity is usually estimated by the cross-spectrum of acoustic pressure at two adjacent microphones. The cross-spectrum calculated by digital Fourier transform technique will unavoidally have leakage error since the period of signal will not be usually coincident with record length. Therefore, the acoustic intensity estimated by the conventional FFT analyzer will show distorted value. In this paper, the expression of the Fourier transformed date of a harmonic signal with a single frequency is formated when there is leakage error. The method to elimate the effect of leakage error from the contaminated data is also proposed. Some numerical examples show the validation of the proposed method.

• 로봇학회논문지
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• 제11권3호
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• pp.146-155
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• 2016

Localization of underwater vehicle is essential to use underwater robotic systems for various applications effectively. For this purpose, this paper presents a method of two-dimensional SLAM for underwater vehicles equipped with two hydrophones. The proposed method uses directional angles for underwater acoustic sources. A target signal transmitted from acoustic source is extracted using band-pass filters. Then, directional angles are estimated based on Bayesian process with generalized cross-correlation. The acquired angles are used as measurements for EKF-SLAM to estimate both vehicle location and locations of acoustic sources. Through these processes, the proposed method provides reliable estimation for two dimensional locations of underwater vehicles. Experimental results demonstrate the performance of the proposed method in a real sea environment.

• 대한의용생체공학회:의공학회지
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• 제32권3호
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• pp.264-269
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• 2011

To increase therapeutic efficiency and biological safety, it is important to precision control of acoustic output for therapeutic ultrasound equipment. In this paper, the electro-acoustic radiation conductance, one of electroacoustic characteristics of therapeutic ultrasound equipment, was measured by the radiation force balance method according to IEC 61161 standards and the acoustic output was estimated using the electro-acoustic radiation conductance. The estimation of acoustic output was conducted to continuous wave mode and pulse wave mode of duty cycle between 20% and 80%. The differences between prediction values and measurement results are within 5% of measurement uncertainty, which is a reasonably good agreement. The results show that acoustic output controlled by electro-acoustic radiation conductance was found to be an effective method.

• 한국음향학회지
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• 제22권5호
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• pp.345-350
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• 2003

음향 인텐시티는 근접한 두 개의 마이크로폰으로부터 얻어지는 음압의 크로스스펙트럼으로부터 얻어진다. 크로스스펙트럼은 이산 푸리에 변환에 의해 얻어지는데 이는 기록시간과 신호의 주기가 일반적으로 일치하지 않기 때문에 누설오차의 발생을 피할 수 없다. 그러므로 기존의 FFT 해석기로부터 얻어지는 음향 인텐시티는 왜곡된 값을 보여준다. 본 논문에서는 단일주파수를 가지는 조화 신호에 누설오차가 발생한 경우 푸리에 변환된 데이터를 규정한다. 또한 왜곡된 데이터로부터 누설오차의 영향을 제거하는 방법을 제안한다. 제안한 방법의 타당성을 보이기 위해 몇 가지 수치해석 예를 보인다.

• 한국군사과학기술학회지
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• 제12권3호
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• pp.282-289
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• 2009

This paper presents an estimation technique of the equivalent circuit parameters for an underwater acoustic piezoelectric transducer from the measured impedance. Estimated equivalent circuit can be used for the design of the impedance matching network of the sonar transmitter. A fitness function is proposed to minimize the error between the calculated impedance of the equivalent circuit and the measured impedance of the transducer. The equivalent circuit parameters are estimated by using the fitness function and the PSO(Particle Swarm Optimization) algorithm. The effectiveness of the proposed method is verified by the applications to a sandwich-type transducer and a dummy load. In addition, the impedance matching network is also designed by using the estimated equivalent circuit model.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.763-766
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• 2004

Recently, various acoustic artifacts that contains speaker have been produced such as cellular phone. Speaker consists of diaphragm generating sound and coil vibrating diaphragm. Generally, good speaker means that it has a wide frequency range, high output power rate to input power and flat sound pressure level in specified frequency range. Acoustic characteristic was estimated through the experiment and computer simulation, or sound power was controlled with acoustic sensitivity in a natural frequency range fer last decade. However, the flatness of sound pressure level has not been considered to enhance the sound quality of a speaker. Tn this study, a method for speaker design is proposed for a good acoustic characteristic, which is flatness of SPL(sound pressure level) and wideness between the first and second natural frequency. SYSNOISE is used fer acoustic analysis and ANSYS is used for harmonic response analysis and modal analysis. Optimization for acoustic characteristics of a speaker diaphragm is performed using ModelCenter. All analyses are done within a frequency domain. And we confirm that the experimental and computational simulations have similar trend.

• 한국음향학회지
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• 제29권6호
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• pp.402-409
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• 2010

본 논문에서는 주파수 영역에서 결합된 음향학적 반향 및 배경 잡음 전력에 기반한 효과적인 새로운 통합 제거 알고리즘을 제안한다. 제안된 방법에서는 반향 제거기와 배경잡음 제거기가 직렬로 연결되어 각각의 제거필터에 의해 처리되는 기존의 방법 대신에 원단 (far-end) 신호에 기반한 기중치 파라미터를 이용하여 반향 및 배경잡음 전력을 선별적으로 결합하고 결합된 신호를 하나에 제거 필터에 적용하여 두 신호를 모두 제거한다. 따라서 제안된 기법에서는 기존의 반향 및 잡음 제거기의 연결 순서에 의해 발생되는 단점을 보완하고 잔여반향신호를 효과적으로 제거할수 있도록 한다. 제안된 알고리즘은 기존의 방법과 객관적인 실험을 통해 비교 평가한 결과 다양한 테스트 환경에서 기존의 방법에 비해 전반적으로 우수한 성능을 보였다.

• 한국어업기술학회:학술대회논문집
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• 한국어업기술학회 2009년도 춘계학술대회 논문집
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• pp.38-41
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• 2009

The jellyfish Nemopilema nomurai has occurred in large numbers in Japan and Korea and has had on a negative effect on coastal fisheries in this region. Data on the abundance and distribution of jellyfish are needed to forecast when and where they will occur in coastal areas. Acoustic techniques are commonly used to study the distribution and abundance of fish and zooplankton. However before such surveys can be conducted, the acoustic characteristics of the target species must be known. In this study, the density of and speed-of-sound in jellyfish were measured to clarify their acoustic characteristics using a theoretical scattering model. The acoustic characteristics were estimated with the distorted-wave Born approximation (DWBA) model using these material properties and the shape of free-swimming jellyfish.

• 한국수산과학회지
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• 제43권1호
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• pp.83-88
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• 2010

Acoustic telemetry is a useful method to investigate fish behavior and is widely used to obtain biological information. In this study, the detection ability of a mooring-type acoustic telemetry system and the seasonal changes were studied for survey design and data analysis. The system detection range was examined with an underwater noise model, and seasonal changes were estimated with a ray-tracing program and underwater temperature profile data. The field experiment was conducted with two sets of pingers and six receivers to estimate the difference in detection rate by installation depth and to compare the model estimate. Results indicated that the long-range detection ability of the acoustic telemetry system was significantly affected by underwater temperature. The detection rate rapidly decreased near the sea surface or bottom despite that the near-range Signal to noise ratio was sufficient.