• Title/Summary/Keyword: Acoustic Radiation Pattern

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Directional Radiation Pattern Design Using Structural-Acoustic Coupling (구조-음향 연성현상을 이용한 지향성 방사패턴 설계)

  • Seo, Hee-Seon;Kim, Yang-Hann
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.11a
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    • pp.751-754
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    • 2004
  • This paper presents a design of the directional radiation pattern by using the structural-acoustic interaction. For this purpose, prediction of the pressure distribution of the field points and radiation pattern of the structural-acoustic coupling system is shown. In order to get a strong coupling, coupled system that has a finite space and a semi-infinite space separated by two flexible walls and an opening is selected. A volume interaction can be occurred in structure boundary and a pressure interaction can be happened in the opening boundary. The coupled system is maximized the radiation power on the main axis and minimized the side lobe level.

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A Prediction of Radiation Power for the Planar Array Acoustic Transducer Considering Mutual Coupling Effects (상호 간섭 영향을 고려한 평면 배열형 음향 트랜스듀서의 방사 출력 예측)

  • Lee, Jong-Kil;Seo, In-Chang
    • The Journal of the Acoustical Society of Korea
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    • v.15 no.1
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    • pp.17-22
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    • 1996
  • Planar array of acoustic transducer is normally used in a sonar system. Acoustic radiation makes beam pattern in underwater uses. The main source of the beam pattern is due to the transducer array. Therefore, estimation of the acoustic radiated power is necessary to predict the performance and efficiency of the transducer. As an example of the acoustic radiation power, nine acoustic transducers mounted to a rigid infinite baffle are considered in a theoretical model. Each piston's acoustic radiation consists of self- and mutual-radiation impedances. Total radiation impedances and acoustic radiation power of the transducers are extracted using on the theory of an equivalent electric circuit. The theoretical results reveal that acoustic radiation power of the transducer depends on the mutual coupling effects.

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A New Extraction Method for the Radiation Efficiency and Radiation Directional Coefficient (방사효율과 방사방향 계수에 대한 새로운 산출기법 연구)

  • Jung, Woo-Jin;Lee, Jong-Ju;Kang, Myung-Hwan;Jeon, Jae-Jin
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.2
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    • pp.93-101
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    • 2014
  • Underwater radiated noise is the key in acoustic stealth performance of modern naval ships. The underwater radiated noise predicted by the hull vibration with radiation efficiency cannot always give the information of radiation pattern which is essential to analyze of detection probability by enemy and to improve the operational performance of the naval ship. The radiation pattern of underwater radiated noise is able to be obtained with radiation efficiency and radiation directional coefficient. In this paper, a new method to extract the radiation efficiency and radiation directional coefficient is suggested and proved with the simulation and experiment by using cylindrical shell of 70 cm diameter in air.

A Study on the method for the extraction of the radiation efficiency and radiation direction coefficient (방사효율과 방사방향 계수 산출기법 연구)

  • Jung, Woo-Jin;Kang, Myung-hwan;Lee, Jong-Ju;Jeon, Jae-Jin
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2013.10a
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    • pp.738-743
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    • 2013
  • Underwater radiated noise is the key in acoustic stealth performance of modern naval ships. The underwater radiated noise predicted by the hull vibration with radiation efficiency cannot give the information of radiation pattern which is essential to the analysis of detection possibility by enemy and to improve the operational performance of the naval ship. The radiation pattern of underwater radiated noise is able to be obtained with radiation efficiency and radiation direction coefficient. In this paper, a new method to extraction the radiation efficiency and radiation direction coefficient is suggested and proved with the simulation and experiment by using cylindrical shell of 70cm diameter in air.

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Acoustic Radiation Characteristics from Flexible Steel Plate Excited by Acoustic Loading in an Rectangular enclosure (음향 가진된 밀폐계의 유연한 평판의 음향 방사 특성에 관한 연구)

  • 김상헌;안지훈;오재응
    • Journal of KSNVE
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    • v.7 no.3
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    • pp.457-466
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    • 1997
  • The experimental and analytical study was conducted to determine the noise transmission characteristics of acoustically loaded steel plate of rectangular enclosure and to investigate the sound radiation characteristics through out the enclosure. The vibrations of acoustically loaded plate give rise to sound radiations and generate the reverberant space that the sound field exists very close to a vibrating plate. Acoustic transmission loss is measured from the incident intensity into the plate and the transmitted intensity through out the plate. Sound radiation patterns are measured from both acoustic intensity technique and surface intensity technique. Those resultant patterns and vibrational modes are vital in understanding the relations between vibration and noise in the near field out of vibrating plate.

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A Design Method for Direction Selective Structural-acoustic Coupled Radiator (구조-음향 연성현상을 갖는 방사 방향을 가질 수 있는 방사체 설계방법)

  • Seo, Hee-Seon;Kim, Yang-Hann
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.2 s.95
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    • pp.225-231
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    • 2005
  • This paper presents a design method for the structural-acoustic coupled radiator that can emit sound in the desired direction. A coupled system that has a finite space and a semi-infinite space separated by two flexible walls and an opening is considered. An objective function is selected to maximize radiation power on a main axis and minimize a side lobe level. To get initial values, prediction of a pressure distribution on field points and radiation pattern of the structural-acoustic coupling system is shown at a coupled-resonant frequency. Three different optimization methods are adapted to design the coupled radiator. Pressure and intensity distribution of the designed radiator is presented.

Computation of the Mutual Radiation Impedance in the Acoustic Transducer Array: A Literature Survey

  • Paeng, Dong-Guk;Bok, Tae-Hoon;Lee, Jong-Kil
    • The Journal of the Acoustical Society of Korea
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    • v.28 no.2E
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    • pp.51-59
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    • 2009
  • Mutual radiation impedance becomes more important in the design and analysis of acoustic transducers for higher power, better beam pattern, and wider bandwidth at low frequency sonar systems. This review paper focused on literature survey about the researches of mutual radiation impedance in the acoustic transducer arrays over 60 years. The papers of mutual radiation impedance were summarized in terms of transducer array structures on various baffle geometries such as planar, cylindrical, spherical, conformal, spheroidal, and elliptic cylindrical arrays. Then the computation schemes of solving conventional quadruple integral in the definition of mutual radiation impedance were surveyed including spatial convolution method, which reduces the quadruple integral to a double integral for efficient computation.

Prediction of the Acoustic Performance of a Music Hall Considering the Radiation Characteristics of Korean Traditional Musical Sources (국악음원의 방사특성을 고려한 국악원의 음향 성능 예측)

  • 정철호;이정권;연철호;한찬훈
    • The Journal of the Acoustical Society of Korea
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    • v.23 no.2
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    • pp.146-161
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    • 2004
  • There have been always some difficulties in target setting and conditioning of acoustic performances of the Korean traditional music hall due mainly to the lack of the information on the sound radiation characteristics of Korean musical sources. In this study, the radiation characteristics of four typical Korean traditional musical sources were investigated in precision and their usage was demonstrated: The selected musical sources were Gayageum (string), Daegeum (woodwind), Jango (drum), and Pansori Chang (vocal performance). Each sound source was located at the center of a semi-anechoic chamber and the directivity was determined by the measured sound pressure levels in every 10° angular position, for both vertical and horizontal directions. The directivity pattern of Gayageum varies from a uniform to a complex pattern having many side lobes with the increase of frequency. The main radiation of Daegeum is toward the upward direction. The directivity pattern of Jango is clearly a side-oriented one and the left direction intensity is sharper than its right side at low frequencies. For the Chang, the directivity pattern change from a uniform pattern to a frontally directed one as the frequency goes high. Measured directional and spectral characteristics of traditional Korean music sources were implemented into the computation of architectural acoustic measures for the Busan National Korean Traditional Music Hall which is under construction. Parameters such as RT, SPL, C80, IE, STI were calculated at two receiver positions by using a ray tracing technique. Significant differences in the acoustic measures at receiver positions were observed between the results in using the omni-directional source and the directional one. It is thought that the suggested source data and design method can be used as a basic reference in the future acoustic design of performance halls for the Korean traditional music.

A Numerical Analysis Study on the Estimation of the 3D Underwater Radiated Noise Pattern using the Hull Vibration Signals (선체진동신호를 이용한 3차원 수중방사소음 패턴 산출에 대한 수치해석 연구)

  • Yi, Jong-Ju;Kang, Myung-Hwan;Han, Seung-Jin;Bae, Soo-Ryong;Kim, Jae-Ho;Jung, Woo-Jin
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.10
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    • pp.770-779
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    • 2014
  • In this study, a numerical estimation method for 3D underwater radiated noise pattern using hull vibration and total acoustic power of the vibrating structure in the far-field is proposed. The underwater radiated noise pattern is known to be predicted using the vibration signals and radiation efficiency of each surface patch. But it is very difficult to know radiation efficiency of each surface patch which is one of important factors to calculate the 3D underwater radiated noise pattern. Instead of using radiation efficiency of each patch, the underwater radiated noise level is modified with the total acoustic power of the vibrating structure. The suggested estimation method for underwater radiated noise pattern is discussed with numerical model.

Analysis of Underwater Acoustic Radiation of SWATH vessel using Transfer Function Method (전달함수법을 이용한 SWATH선의 수중 음향 방사 해석)

  • 김재호
    • Journal of the Korea Institute of Military Science and Technology
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    • v.6 no.2
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    • pp.20-34
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    • 2003
  • The good sea-keeping capability of the SWATH(Small Waterplane Area Twin Hull) ship has been attractive for research or surveillance vessels. Especially, for the naval ships accomplishing the underwater acoustic missions, it is necessary to access and minimize the underwater radiated noise level generated by the ships. Therefore, acoustic signature management and control are very important topics for these vessels. Underwater radiation pattern in the low frequency range is dominated by the tonals from the vibration of onboard machinery. In this work, the radiated noise level generated by the propulsion machine in the submerged hull is predicted using the transfer function technique and the hull transfer function for the submerged hull is determined by analyzing the longitudinal/circumferential stiffened infinitely long cylindrical shell and considering the empirical database of the previous vessels. It is confirmed that the transfer function technique can give useful information for identifying the noise source and estimating its contribution to the total radiatied noise level.