• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.569-569
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• 2014

The interior vehicle noise due to the exterior aerodynamic field is an important topic in the acoustic design of a car. The air flow detached from the A-pillar and impacting the side windows are of particular interest as they are located close to the driver / passenger and provides a lower insulation index than the trimmed car body parts. This paper presents a numerical analysis method for a simplified vehicle model. The internal air cavity including trim component are included in the simulation. The car body includes the windshield and two side windows. The body is made of aluminum and trimmed with porous layers. The methodology proposed in this paper relies on two steps: the first step involves the computation of the exterior flow and turbulence induced non-linear acoustic field using CFD Code. The second step consists in the computation of the vibro-acoustic transmission through the window using the finite element vibro-acoustic solver Actran.

• 한국정밀공학회지
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• 제17권1호
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• pp.101-109
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• 2000

Mutual torque ripple in a brushless DC motor is the main source of acoustic noise, especially fur motor operation with high speed and torque. This paper presents a method to obtain mutual torque ripple to identify acoustic noise source. Mutual torque ripple can be determined by analyzing phase current shape and magnetic circuit with different lead angles. Current shape is determined by state space model of voltage equation with the use of inductance calculated by FEM, and confirmed by experimental results. Mutual torque ripple is also determined by FEM analysis for the calculated current shape. Acoustic noise experiment reveals that mutual torque ripple with different lead angle is one of the main sources for noise generation in a brushless DC motor.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 추계학술대회 논문집
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• pp.398-404
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• 1998

The acoustic power reduction methods of the vibrating structures are valid to design the quite structure. To calculate the acoustic power, the dynamic responses have to be determined. It is not easy to analyse the structure composed of the corrugated panels. Because of the structural complexity and the many analysing times. To make up for these defects, the equivalent orthogonal panel is presented. Also the acoustic power prediction method of the vibrating structures is proposed. As examples, the equivalent material properties of the corrugated plates are obtained and the acoustic powers of the floor structure are calculated at several frequency regions for KHST.

• 수산해양기술연구
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• 제53권2호
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• pp.152-159
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• 2017

Rockfish was a commercially important fish specie in marine ranching areas in Korea. To estimate density and biomass of rockfish using acoustic method, target strength (TS) information is required on the species. This study measured TS dependence on tilt angle and size on 14 live rockfish individuals at 38, 70, and, 120 kHz by ex-situ measurement (tethered method) and acoustic scattering model (Krichhoff ray mode, KRM). The swimbladdered angle ranged from 18 to $30^{\circ}$ ($mean{\pm}s.d.=26{\pm}4^{\circ}$). The mean TS for all individuals was highest -35.9 dB of tilt angle $-17^{\circ}$ at 38 kHz, -35.4 dB of tilt angle $-25^{\circ}$ at 70 kHz, and -34.9 dB of tilt angle $-22^{\circ}$ at 120 kHz. The ex-situ TS-total length (TL, cm) relationships were $TS_{38kHz}=20log_{10}(TL)-67.1$, $TS_{70kHz}=20log_{10}(TL)-68.6$, and $TS_{120kHz}=20log_{10}(TL)-69.9$, respectively. The model TS-total length (TL, cm) relationships were $TS_{38kHz}=20log_{10}(TL)-66.4$, $TS_{70kHz}=20log_{10}(TL)-67.0$, $TS_{120kHz}=20log_{10}(TL)-67.0$. The two measurements between the ex-situ TS and KRM model for TS-tilt angle and fish size were found to be significantly correlated.

• 한국산학기술학회논문지
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• 제12권7호
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• pp.3267-3274
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• 2011

최근 다양한 모바일 기기의 사용자 환경과 다양한 음성인식 소프트웨어의 영향으로 음성인식 기술역시 빠르게 발전되고 있다. 그러나 다국어를 대상으로 하는 음성인식의 경우 다국어 혼합음성에 대한 이해 부족과 시스템 성능의 한계로 인하여 원활한 인식율의 개선은 이루어지지 않고 있다. 여러 나라의 혼합 언어로 표현된 음성의 경우 하나의(단일) 음성모델로 구현하는 것이 쉽지 않고, 또한 여러 개의 음성모델을 사용한 시스템의 경우 음성인식 성능의 저하라는 문제점이 있다. 이에 따라 다양한 언어로 구성되어 있는 음성을 하나의 음성모델로 표현할 수 있는 다국어 음성인식 모바일 시스템의 개발 필요성이 증가되고 이에 대한 연구가 필요하다. 본 논문에서는 모바일 시스템에서 다국어 혼합 음성모델을 사용하기 위한 기본연구로써 한국어와 영어 음성을 국제 음성기호(IPA)로 인식하는 통합음성모델 시스템 구축을 연구하였고, 한국어와 영어 음소를 동시에 만족하는 IPA모델을 찾는데 중점을 두어 실험한 결과 우리말 음성은 94.8%, 영어 음성은 95.36%라는 인식률을 얻을 수 있었다.

• 한국소음진동공학회논문집
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• 제13권11호
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• pp.882-889
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• 2003

This paper presents the method for structure borne noise analysis of a flexible body in multibody system. The proposed method is the superposition method using the flexible multibody dynamic analysis and the finite element one. This method is executed in 3 steps. In the 1st step, time dependent quantities such as dynamic loads, modal coordinates and gross body motion of the flexible body are calculated through a flexible multibody dynamic analysis. And frequency response functions of those time dependent quantities are computed through Fourier transforms. In the 2nd step, acoustic pressure coefficients are obtained through structure-acoustic coupling analyses by the finite element method. In the final step, frequency responses of acoustic pressure at the acoustic nodes are recovered through linear superposition of frequency response functions with acoustic pressure coefficients. The accuracy of the proposed method is verified in the numerical example of a simple car model.

• 한국멀티미디어학회논문지
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• 제12권2호
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• pp.281-289
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• 2009

본 논문에서는 공간 스케치에 일반적으로 나타나는 깊이 입력 오차를 줄이는 효과적인 공간 입력을 구현하기 위해 깊이 값 인지를 도와주는 한 면 혹은 두 면의 가상 음향 반향판을 통한 새로운 상호작용 기술을 소개하고, 다양한 실험을 통해 음향 반향판을 가진 가상의 벽이 현실적인 가상 개념 디자인을 위한 효과적인 피드백으로 사용된 것을 보여 준다. 제안된 아이디어를 이용하여 깊이 값이 일정한 평면에서는 한 면 가상 음향 반향판의 피드백을 이용하여 모델과의 일치도를 약 35% 높일 수 있었고, 기울어진 평면에서는 두면 반향을 이용하여 한 면에 비해 악 4%의 일치도를 증가시킬 수 있었으며, 곡면 꽃병에서는 약 15%의 일치도를 증가시킬 수 있었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.17-20
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• 2007

연소실내 형성되는 접선방향 음향 모드의 감쇠를 위해 장착되는 공명기의 반경 방향 위치 효과에 대해 실험적으로 연구하였다. 반파장 공명기를 채택하였고, 상온에서 선형 음향 실험을 수행하였다. 감쇠 대상 음향 모드에 대해 공명기가 최적의 길이를 갖는 경우에는, 반경 방향 위치의 증가에 따라 음향 감쇠 효과가 증가하였다. 또한, 반경방향으로의 감쇠 인자의 변화 추이는 감쇠시키고자 하는 음향 모드의 진폭 변화 추이와 유사하였다. 장착 위치가 장착변의 중심에 접근할수록 음향 감쇠 효과가 감소할 뿐만 아니라 분사기 길이와의 상관성도 감소하였다. 공명기가 비최적 길이를 갖는 경우에는, 반경 방향 위치 효과가 거의 나타나지 않아 위치와 무관한 감쇠 인자값을 관찰할 수 있었다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2005년도 학술발표회 논문집
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• pp.68-73
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• 2005

In succession of the previous works, seismo-acoustic analysis was conducted to collect ground truth events and to discriminate surface explosions from natural earthquakes in the Korean Peninsula for 2004. In this period, total 510 seismo-acoustic events corresponding to 10.8 percent of total seismic events occurred in and near the Korean Peninsula were analyzed and discriminated as artificial surface explosions. Events distribution of the seismo-acoustic events in 2004 is similar to the previous results of 1999-2003. And newly determined seismo-acoustic events were added to the surface explosions database. To extend infrasound detection capability, Korea Institute of Geoscience and Mineral Resources (KIGAM) and Southern Methodist University (SMU) installed new seismo-acoustic array (BRDAR) in Baekryoung Island last November, 2004. The array configuration and design is nearly same to previous seismo-acoustic arrays CHNAR, KSGAR, a triangular 1 km aperture. BRDAR consists of 5 short period vertical seismometers (GS-13) in seismic vaults and 13 microbarometers (Chaparral Model 2). Preliminary analysis using data collected from BRDAR shows an extension of infrasound detection capability to western part of the Korean Peninsula. Also, multiple observations of infrasound at BRDAR and other arrays gave an opportunity to localize sound source regions.

• 로봇학회논문지
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• 제12권4호
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• pp.402-410
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• 2017

Acoustic based localization is essential to operate autonomous robotic systems in underwater environment where the use of sensorial data is limited. This paper proposes a localization method using artificial underwater acoustic sources. The proposed method acquires directional angles of acoustic sources using time difference of arrivals of two hydrophones. For this purpose, a probabilistic approach is used for accurate estimation of the time delay. Then, Gaussian sum filter based SLAM technique is used to localize both acoustic sources and underwater vehicle. It is performed by using bearing of acoustic sources as measurement and inertial sensors as prediction model. The proposed method can handle directional ambiguity of time difference based source localization by generating Gaussian models corresponding to possible locations of both front and back sides. Through these processes, the proposed method can provide reliable localization method for underwater vehicles without any prior information of source locations. The performance of the proposed method is verified by experimental results conducted in a real sea environment.