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  • Comparative Studies. Non-European Languages/Literatures  (26)
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  • Comparative Studies. Non-European Languages/Literatures  (26)
RVK
  • 1
    Online Resource
    Online Resource
    A stepped plate transducer as ultrasonic range sensor
    Acoustical Society of America (ASA) ; 2008
    In:  The Journal of the Acoustical Society of America Vol. 123, No. 5_Supplement ( 2008-05-01), p. 3649-3649
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 123, No. 5_Supplement ( 2008-05-01), p. 3649-3649
    Abstract: A new type of highly directional ultrasonic transducer is designed and tested as an ultrasonic range sensor by using the parametric acoustic arrays. To get intensive primary waves, a modified stepped plate transducer is proposed. Gallego-juarez et al.(1978) first proposed stepped plate transducer for high power radiation at one frequency. The steps with the height of half-wavelength of sound in air compensate discrete phase difference on the vibrating plate. However, two collimated beams are required for the parametric acoustic array. The position and height of the steps are modified to compensate the flexural vibration for two frequencies in this transducer. The transducer diameter is 50mm. The optimal primary frequencies are designed as 80kHz and 120kHz to generate difference frequency of 40kHz efficiently. The proposed transducer has the HPBW of 5° that is much higher directivity than general ultrasonic range sensor(Generally 20° on same size). The maximum SPL is 130dB at primary frequencies and 95dB at difference frequency on 75Vpk input. These experimental results show that the proposed transducer can successfully improve the spatial resolution of ultrasonic sensor. [Research is partly supported by MIC/IITA Intelligent Robot Sensor and partly supported by DAPA and ADD UD070054AD]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.2934934
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2008
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  • 2
    Online Resource
    Online Resource
    A stepped-plate bi-frequency source for generating a difference frequency sound with a parametric array
    Acoustical Society of America (ASA) ; 2010
    In:  The Journal of the Acoustical Society of America Vol. 127, No. 6 ( 2010-06-01), p. 3494-3502
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 127, No. 6 ( 2010-06-01), p. 3494-3502
    Abstract: An ultrasonic radiator is developed to generate a difference frequency sound from two frequencies of ultrasound in air with a parametric array. A design method is proposed for an ultrasonic radiator capable of generating highly directive, high-amplitude ultrasonic sound beams at two different frequencies in air based on a modification of the stepped-plate ultrasonic radiator. The stepped-plate ultrasonic radiator was introduced by Gallego-Juarez et al. [Ultrasonics 16, 267–271 (1978)] in their previous study and can effectively generate highly directive, large-amplitude ultrasonic sounds in air, but only at a single frequency. Because parametric array sources must be able to generate sounds at more than one frequency, a design modification is crucial to the application of a stepped-plate ultrasonic radiator as a parametric array source in air. The aforementioned method was employed to design a parametric radiator for use in air. A prototype of this design was constructed and tested to determine whether it could successfully generate a difference frequency sound with a parametric array. The results confirmed that the proposed single small-area transducer was suitable as a parametric radiator in air.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.3397445
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2010
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  • 3
    Online Resource
    Online Resource
    A new lumped parameter model for the design of the free-flooded ring transducer
    Acoustical Society of America (ASA) ; 2017
    In:  The Journal of the Acoustical Society of America Vol. 142, No. 4_Supplement ( 2017-10-01), p. 2509-2509
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 142, No. 4_Supplement ( 2017-10-01), p. 2509-2509
    Abstract: The free-flooded ring (FFR) transducer is the well-known low-frequency sound sources in underwater because its operating frequency bandwidth is broad and relatively small size. Previous researches were preformed to predict the characteristics of FFR transducers using ECM which is a type of LPM because ECM is widely used to understand its characteristics in transducer design process. However, it is hardly to predict the characteristics of an FFR transducer because the acoustic field is generated from its top and bottom openings, connected by the inner fluid, as well as the cylindrical ring surface. Here, the authors investigated an ECM of an FFR transducer consisting of three parts: the piezoelectric ring, the cylindrical cavity, and the radiation load. In addition, an LPM which can consider mutual radiation loads was proposed to improve the accuracy of the model. The proposed models were verified using commercial finite element method (COMSOL Multiphysics). It was confirmed that LPM could predict characteristics of FFR transducer more accurately than ECM. [Work supported by NRF 2016R1E1A2A02945515).]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.5014163
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2017
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  • 4
    Online Resource
    Online Resource
    A piezoelectric micromachined ultrasonic transducer array for parametric loudspeakers
    Acoustical Society of America (ASA) ; 2013
    In:  The Journal of the Acoustical Society of America Vol. 134, No. 5_Supplement ( 2013-11-01), p. 4122-4122
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 134, No. 5_Supplement ( 2013-11-01), p. 4122-4122
    Abstract: A parametric array is a nonlinear conversion process that can generate a highly directional sound beam with a small aperture. Since parametric sound generation requires high-intensity ultrasound for nonlinear interaction, efficient sound generation is an important issue in the practical use of parametric loudspeakers. In this study, a piezoelectric micromachined ultrasonic transducer array was investigated in order to generate directional audible sound with a parametric array. A piezoelectric micromachined ultrasonic transducer, with a micron-thick radiating plate, was verified to generate ultrasound with high-efficiency in air. Two types of unit transducers with different resonance frequencies (f1 = 100 kHz, and f2 = 110 kHz) were arranged in the transducer array to extend the frequency bandwidth. The electroacoustic efficiency of the transducer was measured to 71% at its resonance frequency. The ±3dB-frequency bandwidth of the transducer array was 17 kHz. The spatial distributions of the difference frequency wave were measured and compared with the computed data in the audible frequency range. The fabricated transducer array consumed 1 W of electric power while generating a 10 kHz-difference frequency wave with sound pressure level of 80 dB.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4831145
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2013
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  • 5
    Online Resource
    Online Resource
    Effects of mutual impedance on the radiation characteristics of transducer arrays
    Acoustical Society of America (ASA) ; 2004
    In:  The Journal of the Acoustical Society of America Vol. 115, No. 5_Supplement ( 2004-05-01), p. 2526-2526
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 115, No. 5_Supplement ( 2004-05-01), p. 2526-2526
    Abstract: The mutual resistance of transducer arrays is investigated in order to design arrays with improved performance for high intensity sounds at a given frequency. This work proposes the theory that the mutual resistance is related to the loading effects of pressure waves propagated from a piston driver on the surface of another driver. Using this interpretation, the important characteristics of the mutual resistance of two piston drivers are explained and the conditions for local maxima in the mutual resistance are easily determined. On the basis of analyses of the interactions between a driver and acoustic pressure waves, we propose a method to determine the driver radius and the distance between two drivers that give maximum mutual radiation resistance. To evaluate the proposed method, the total resistance of a transducer array is calculated using the formulas for mutual and self-resistance established by Pritchard. The results of the calculations of the total resistances of arrays with many drivers show that a transducer array with drivers arranged sparsely can achieve a larger value of the radiation power per unit area as well as better radiation efficiency than an array in which the drivers are in a closely packed arrangement at a given frequency.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4783349
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2004
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  • 6
    Online Resource
    Online Resource
    A micro-machined microphone based on field-effect-transistor and electrets
    Acoustical Society of America (ASA) ; 2011
    In:  The Journal of the Acoustical Society of America Vol. 130, No. 4_Supplement ( 2011-10-01), p. 2464-2464
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 130, No. 4_Supplement ( 2011-10-01), p. 2464-2464
    Abstract: Micro-machined microphones are attracting attention of industry because of their benefit of size over conventional ones. Since most of micro-machined microphones are capacitive sensors, the sizes of their electrodes determine the low frequency noise level that increases with inverse of frequency (1/f). Therefore, the size of microphone itself becomes larger than one that can be fabricated. Here, we introduce a micro-machined microphone that can overcome the limit of capacitive microphones. The proposed microphone is composed of a field-effect-transistor (FET) and an electret. The difference between the conventional electret capacitive microphones and the proposed microphone may be the transduction mechanism: The change in the position of an electret causes the change in electric field on the gate of FET. Compared with capacitive transduction, the resistive channel of FET can be designed to have low sensor impedance, and subsequently have low impedance at low frequency. To make experimental specimen, FET onto membrane and electret was fabricated with conventional metal-oxide-semiconductor fabrication process and micromachining process, respectively. The FET membrane chip and the electret chip were assembled. Simple current to voltage converter was applied as a pre-amplifier. Its feasibility to apply low frequency acoustic sensor will be proved by simulation and experimental results.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.3654893
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2011
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  • 7
    Online Resource
    Online Resource
    Fluctuation of acoustic signals due to internal waves in the East Sea of Korea
    Acoustical Society of America (ASA) ; 2012
    In:  The Journal of the Acoustical Society of America Vol. 131, No. 4_Supplement ( 2012-04-01), p. 3488-3488
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 131, No. 4_Supplement ( 2012-04-01), p. 3488-3488
    Abstract: This study attempts to investigate the fluctuation of underwater acoustic signals due to internal waves (IWs) off the east coast of Donghae, Korea. Sea experiment was performed with thermistor strings, a sound source, and an array of hydrophones. Based on the thermistor string data, the IWs have characteristics of typical periods of 10-20 minutes, amplitudes of 10-20m, and a duration of 1-2 hours. The IWs were analyzed as they moved from offshore to the coast at a speed of 70 cm/sec. Underwater acoustic signals (CW 80 - 800Hz) also show obvious energy fluctuations with the IWs. Through an analysis of these acoustic signals, fluctuations of periods of 15 minutes are located in time domain. As mixed layer depth varies with time, it may cause travel time difference of acoustic signals. This travel time differences causes fluctuation of acoustic signals in range-independent stratified ocean structure. The spectrum characteristics of the acoustic signals show the possibility that acoustic waves may react to the IWs through mechanisms such as mode coupling and travel time fluctuation.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4709171
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2012
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  • 8
    Online Resource
    Online Resource
    The piezoelectric thickness mode hydrophone using tonpilz structure for deep-sea application.
    Acoustical Society of America (ASA) ; 2009
    In:  The Journal of the Acoustical Society of America Vol. 125, No. 4_Supplement ( 2009-04-01), p. 2594-2594
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 125, No. 4_Supplement ( 2009-04-01), p. 2594-2594
    Abstract: A piezoelectric thickness mode hydrophone for deep-sea application using tonpilz structure was designed, and its macroprototype was made as a preliminary for the micromachined version. Several types of micromachined thin-diaphragm sensors for hydrophone application have been reported. They have two issues in deep-sea applications. One is a sensitivity problem. To enhance the sensitivity, a cone structure for sound pressure amplification was placed between the clamped diaphragm and the piezoelectric square plate. To evaluate the effect of the cone structure on sensitivity, which was motivated by tonpilz structure, an air-backed prototype was made using aluminum and piezoelectric ceramic square plate of 700 μm length and 400 μm thickness. A lumped parameter model was used in the design procedure. The measured sensitivity of the prototype was −249.60 dB ref. One volt per micropascal without a preamplifier, and the measured resonant frequency was 30 kHz, which agreed with the prediction. The other is an endurance problem due to high hydrostatic pressure. To develop the endurance for the high hydrostatic pressure in deep-sea, PZT thickness mode and oil-backing on the diaphragm backside were proposed. The comparison of oil-backing and air-backing is to be presented as an evaluation of the endurance development. [Research supported by MRCnd.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4783867
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2009
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  • 9
    Online Resource
    Online Resource
    Efficiency analysis on a piezoelectric micro-machined ultrasonic transducer as a high intensity wave generator in air
    Acoustical Society of America (ASA) ; 2012
    In:  The Journal of the Acoustical Society of America Vol. 131, No. 4_Supplement ( 2012-04-01), p. 3498-3498
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 131, No. 4_Supplement ( 2012-04-01), p. 3498-3498
    Abstract: It is difficult to efficiently produce high-intensity acoustic/ultrasonic waves in air with a conventional piezoelectric transducer because of the huge acoustic impedance mismatch between solid-state transducers and air. In this work, the mechanoacoustic efficiency of a thin-plate flexural mode transducer is analytically compared with that of a conventional 1/4ƛ thickness mode vibrator. Radiation and internal mechanical quality factors are applied in the analysis. In the case of the thickness mode piezoelectric vibrator, the radiation quality factor does not depend on design factors, but only on material properties. Consequently, the mechanoacoustic efficiency of the thickness mode vibrator depends only on the material properties, and is less than 3% for most piezoelectric ceramics. For a thin-plate flexural mode transducer, the radiation quality factor can be controlled by the aspect ratio of the thin-plate, which is one of design parameters. Theoretically, the mechanoacoustic efficiency of the flexural mode transducer can be designed to be nearly 100% at the resonance frequency. By experimental analysis, the mechanoacoustic efficiency of the micro-machined transducer was about 65.9%, and the overall electroacoustic efficiency was 58.4% in the resonance. The transducer arrays designed based on this analysis have been successfully applied in parametric array applications in air.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4709217
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2012
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  • 10
    Online Resource
    Online Resource
    A micromachined piezoelectric flexural mode hydrophone for audible frequency application.
    Acoustical Society of America (ASA) ; 2009
    In:  The Journal of the Acoustical Society of America Vol. 125, No. 4_Supplement ( 2009-04-01), p. 2595-2595
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 125, No. 4_Supplement ( 2009-04-01), p. 2595-2595
    Abstract: A micromachined hydrophone is designed for audible frequency application (20 Hz–20 kHz). The basic structure is a flexural unimorph consisting of a clamped silicon diaphragm and a piezoelectric film. Two design approaches can enhance its sensitivity. One is a unimorph with unequal radii between the piezoelectric film and the diaphragm, which increases electromechanical coupling. The other is an air-backed chamber, which reduces mechanical impedance in the flexural vibration and, consequently, enhances sensitivity. To predict the effects of these approaches on sensitivity, an equivalent transduction model is composed and used for calculations. In the case of oil backing, compared to air backing, a reduction in sensitivity of about 40 dB is expected. The dimensions of the micromachined diaphragm (piezoelectric film) are 630 μm (400 μm) radius and 15 μm (3 μm) thick. A fabricated microsensor is constructed as a hydrophone by using a rubber housing filled with castor oil. The measured sensitivity is −228.3 dB at 1V/μPa without a preamplifier. A flat frequency response within ±1 dB deviations were measured in the 100 Hz–5 kHz band. Based on the simulation, it can resist the hydrostatic pressure of 100 m depth, without pressure balancing, while decreasing in sensitivity. The results of a larger model having a higher sensitivity of −207.6 dB will also be presented. [Research supported by MRCND and R0A-2007-000-20042-0.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4783872
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2009
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