• Title/Summary/Keyword: Acoustic window

Search Result 90, Processing Time 0.025 seconds

Trial manufacture of dual frequency acoustic pinger to minimize cetacean bycatch (고래류 혼획을 최소화하기 위한 다주파 음향 경고시스템의 시험 제작)

  • Lee, Yoo-Won;Shin, Hyeong-Il;Kim, Seok-Jae;Seo, Du-Ok;Lee, Dae-Jae;Kim, Zang-Geun;Hwang, Doo-Jin
    • Journal of the Korean Society of Fisheries and Ocean Technology
    • /
    • v.41 no.3
    • /
    • pp.207-212
    • /
    • 2005
  • Dual frequency acoustic pinger(AP) was manufactured to reduce study effect by long-term use of developed single frequency AP to prevent cetacean bycatch. Directivity characteristic of transducer was the omnidirectional pattern which showed less than ${\pm}3dB$ the change range of sensitivity on the beam pattern of right and left. Source power level(SPL) was 1384311pa with epoxy window before casing however after casing 1170B11Pa at sea. Dual frequency Af was tested to identify the avoidance behavior of bottlenose dolphin by its working. However the efficiency of dual frequency AP about the study effect was verified experiment repeatedly using single and dual frequency AP.

Calculation of Radiation Impedance in Consideration of Acoustic window (음향윈도우 영향을 고려한 방사임피던스의 계산)

  • Kim JungSoon;Kim MooJoon;Kim ChunDuck;Ha KangLyeol
    • Proceedings of the Acoustical Society of Korea Conference
    • /
    • autumn
    • /
    • pp.451-452
    • /
    • 2004
  • 본 연구에서는 방사임피던스의 계산에 있어서, 음향윈도우의 물질상수 및 두께의 변화에 따른 영향을 고려하였다. 전송 선로형 등가회로를 방사면과 음향 매질 사이에 삽입함으로써 방사면에서 본 자기 방사임피던스의 변화를 평면 및 곡면 배플에 대하여 계산하고 그 결과를 고찰하였다.

  • PDF

Input Impedance Analysis of Piezoelectric Cylinder Transducer using Finite Element Method (유한요소법을 이용한 원통형 압전변환기의 입력임피던스 해석)

  • 김천덕;서희선;김대환;윤종락
    • The Journal of the Acoustical Society of Korea
    • /
    • v.11 no.6
    • /
    • pp.32-40
    • /
    • 1992
  • This study shows how the finite element method for the structural problems could be applied in the electromechanical impedance analysis of an in-air piezoelectric cylinder transducer and then compares the numerical results by the FEM with the measured results using the impedance analyzer. The results also show that the comparison between both results could be applied to examine the mechanical properties of the added unknown material to transducer such as an acoustic window.

  • PDF

A study on the design of bandpass filters using SAW components (탄성표면파 소자를 이용한 대역통과 여파기의 설계에 관한 연구)

  • 전계석;황금찬;김봉열
    • 전기의세계
    • /
    • v.31 no.2
    • /
    • pp.141-146
    • /
    • 1982
  • In this paper, surface acoustic wave (SAW) bandpass filter is designed using the Fourier series approach and the I$_{0}$-shin window function. And also we studied a method to realize SAW filter using the apodized ID transducer which was fabricated with aluminum metallization of about 1500 A over .deg. thickness on Y-cut Z-propagating LiNbO$_{3}$, crystal by photolithographic technique (lift-off method). Experimental results on SAW bandpass filter responses show good agreements with the theoretical characteristics.s.

  • PDF

Frequency Response Properties of SAW Tansversal Filters by Impulse Modeling (임펄스 모델에 의한 SAW Transversal Filters의 주파수 응답 특성)

  • 손헌영;윤영섭
    • Proceedings of the IEEK Conference
    • /
    • 1999.11a
    • /
    • pp.173-176
    • /
    • 1999
  • Frequency responses of the surface acoustic wave(SAW) filters are simulated by using the impulse modeling. The simulation technique of the SAW filters is to use the Fourier transformation to make a correspondence between the impulse response of the filter and the taps in the delay line. Since the Fourier series must be truncated after a finite number of terms, window functions are often used to weight the coefficients to obtain the desirable side-lobe level and bandwidth. The filter design is operated through the iterative simulation procedures. The design process is capable of yielding filters with optimized frequency response characteristics.

  • PDF

External Flow and Cabin Interior Noise Analysis of Hyundai Simple Model by Coupling CAA++ and ACTRAN

  • Kim, Young Nam;Chae, Jun Hee;Jachmot, Jonathan;Jeong, Chan Hee
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2013.10a
    • /
    • pp.291-291
    • /
    • 2013
  • 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. HMC is interested in the numerical prediction of this aerodynamic noise generated by the car windows with the final objective of improving the products design and reducing this noise. 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 the CAA(Computational aeroacoustics) solver CAA++. The second step consists in the computation of the vibro-acoustic transmission through the side window using the finite element vibro-acoustic solver Actran. The internal air cavity including trim component are included in the simulation. In order to validate the numerical process, an experimental set-up has been created based on a generic car shape. The car body includes the windshield and two side windows. The body is made of aluminum and trimmed with porous layers. First, this paper describes the method including the CAA and the vibro-acoustic models, from the boundary conditions to the different components involved, like the windows, the trims and the car cavity is detailed. In a second step, the experimental set-up is described. In the last part, the vibration of the windshield and windows, the total wind noise level results and the relative contributions of the different windows are then presented and compared to measurements. The influence of the flow yaw angle (different wind orientation) is also assessed.

  • PDF

Sound Insulation Strategy for the Tunnel Noise in a High Speed Train (고속철도차량의 터널 소음을 위한 차음 전략)

  • Kim, Seock-Hyun;Lee, Ho-Jin;Kim, Jung-Tae
    • Journal of the Korean Society for Railway
    • /
    • v.15 no.4
    • /
    • pp.315-322
    • /
    • 2012
  • In a tunnel, interior noise of a high speed train increases by 5dB~7dB. The reason is that the sound intensity of the acoustic field in the tunnel significantly increases by the reflected waves occurred in the closed space. Especially, the incident acoustic power largely increases on the outside of the compartment side panel and large transmission of noise is available through the side panel and the glass window. In this paper, the sound insulation strategy in the tunnel is proposed for the next generation high speed train under development. Specimens of the aluminum extruded panels, layered panels and double glazed window are manufactured and intensity transmission loss is measured according to ASTM E2249-02. Based on the measured data, problems in the sound insulation performance are diagnosed and the sound insulation strategy is reviewed on each panel and layered structures.

Fabrication of Polyurethane-sheet Acoustic Windows and Their Mechanical and Acoustic Properties in Water (폴리우레탄 평판 음향 윈도우 제조와 수중에서 기계적 및 음향적 특성 연구)

  • Cho, Mi-Suk;Choi, Chae-Seok;Lee, So-Jung;Yoon, Suk-Wang;Koo, Ja-Chun;Lee, Young-Kwan
    • Polymer(Korea)
    • /
    • v.34 no.2
    • /
    • pp.104-107
    • /
    • 2010
  • Polyurethane (PU) sheets were fabricated by the reaction of polypropylene glycol (PPG) and liquid diphenyl methane diisocyanate (L-MDI) with various trimethylol propane (TMP) contents. The $T_g$ value was varied from 34.8 $^{\circ}C$ to 49.9 $^{\circ}C$ according to the TMP content. As the content of TMP was increased from 4 to 12 wt%, the modulus of the PU sheet was increased from 322 MPa to 423 MPa, its tensile strength was increased from 10.6 MPa to 14.8 MPa, and its elongation was decreased from 62.8% to 49%. In case of acoustic properties, the sound speed of PU sheet was increased while its attenuation coefficient was decreased as the content of TMP was increased. The fabricated PU sheet was stable in water bath for 4 weeks.

Predicting Noise inside a Trimmed Cavity Due to Exterior Flow (외부 유동에 의한 흡차음재 공간내의 소음 예측)

  • Jeong, ChanHee;Ganty, Bastien;Choi, EuiSung;Cho, MunHwan
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2014.04a
    • /
    • pp.466-471
    • /
    • 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 PowerFlow. The second step consists in the computation of the vibro-acoustic transmission through the window using the finite element vibro-acoustic solver Actran. Additionally in order to validate the numerical process, an experimental set-up has been created based on the simplified vehicle. The vibration of the windshield and windows, the total wind noise level results and the relative contributions of the different windows are then presented and compared to measurements. The influence of the flow yaw angle (different wind orientation) is also assessed.

  • PDF

Design and Evaluations of Underwater Hydrophone with Self Noise Suppressing Structures; - Part Ⅱ. Influence of Acostic Damping Layer Properties - (저 잡음 수중 청음기의 설계 방안 연구 - Ⅱ. 음향 감쇠층 재질의 영향 -)

  • Im, Jong-In;Roh, Young-Rae
    • The Journal of the Acoustical Society of Korea
    • /
    • v.16 no.3
    • /
    • pp.13-17
    • /
    • 1997
  • This paper investigates the influence of material properties of the acoustic damping layer in the low noise hydrophone designed in the previous paper. For increase of the insensitivity of the hydrophone to external noises, acoustic impedance and damping coefficients are selected and the effects of the selected material property on the hydrophone response to the external noises are simulated with finite element method (FEM). The results show that the damping coefficients are not influential to the structural vibration decoupling from the sensing element. On the other hand, the optimum acoustic impedance of compliant layer is estimated which is smaller than 1 Mrayl or larger than 4 Mrayl. However polymer materials, which are in general use for acoustic window and damping layers, is not appropriate for the compliant materials of this hydrophone. Therefore development of new composite materials, i.e. ceramic-polymer composite or metal-ceramic composites etc., is required for the development of effective self noise suppressing underwater hydrophones.

  • PDF