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Journal of the Acoustical Society of America

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Nov 1975

Volume 58, Issue S1, pp. S2-S132

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back to top Session NN. Engineering Acoustics IV
Contributed Papers
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Finite‐element modeling of piezoelectric ceramic hydrophones (A)

R. T. Winnicki and S. E. Auyer

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S79-S79 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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The finite‐element method has been used for several years to predict the response of hydrophones. This paper discusses the application of the technique to the class of hydrophones consisting of right circular air‐filled cylinders of piezoelectric ceramic with semirigid nonpiezoelectric end caps. The acoustic sensitivity of this class of hydrophone can be calculated from a solution developed by R.A. Langenvin [R.A. Langenvin, J. Acoust. Soc. Am. 26, 421–427 (1953)]. This solution assumes an ideal response of the hydrophone which does not include the effects of end cap bending or the restriction of movement of the piezoelectric cylinder at the end‐cap cylinder boundary. The contribution to the hydrophone's acoustic sensitivity of the radial, axial, and circumferential stresses are calculated by the finite‐element method and are used to examine the effects on the hydrophone performance of a nonideal response which includes end‐cap bending and the restriction of cylinder movement at the cylinder end‐cap boundary. A computer generated film depicts the response of an ideal and nonideal hydrophone.
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Electroacoustic modeling of magnetostrictive shells and rings (A)

S. Hanish, B. J. King, R. V. Baier, and P. H. Rogers

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S79-S79 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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The mathematical model of the electroacoustic performance of a force‐driven free‐flooding magnetostrictive cylinder shell used as an underwater sound transducer, originally presented at the 86th Meeting of the Acoustical Society of America in 1973 [J. Acoust. Soc. Am. 55, 471(A) (1974)] and later developed in NRL Report 7767 (Dec. 1974), has been coded into a computer program called EIGSHIP. This program is designed to predict electrical and mechanical impedances of the loaded shell, transmitting responses, electroacoustic efficiency, surface velocities, farfield beam patterns, and other relevant performance parameters. An experimental check on the predictive capabilities of EIGSHIP was undertaken using three specially constructed magnetostrictive shells which were tested under water load conditions in an indoor test facility. A discussion of the comparison of predicted and measured performance is presented. Also samples of typical computer runs are displayed and commented on.
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Magnetostrictive ring transducer technology manual (A)

J. A. Sinsky, R. V. Baier, and B. J. King

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S80-S80 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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A comprehensive magnetostrictive ring transducer designer's manual will be described. The manual consists of three main parts: (1) the highlights of the history of magnetostrictive ring transducer research and development, (2) parameter studies of a large‐flow‐frequency ring transducer and a discussion of related design considerations, and (3) an extensive bibliography from which information in the manual is derived. The manual is written in a style which is appropriate for use by technical administrators and systems analysts as well as transducer engineers. Design curves, tables, and formulas will be discussed which enable the manual user to estimate with “state‐of‐the‐art” accuracy the dimensions of ring transducers which achieve desired performance specifications. Limitations of the manual and the technology is included in the discussion.
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Two‐dimensional finite‐element analysis of electroelastic normal modes of ferroelectric disks and shells (A)

Thomas F. Krile and Harold A. Sabbagh

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S80-S80 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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A variational method, using two‐dimensional finite elements as the basis functions, is used to calculate the short‐circuit and open‐circuit electroelastic normal modes of a radially polarized, ferroelectric shell and an axially polarized, ferroelectric disk. A method by which suitable two‐dimensional piecewise polynomial finite elements are generated will be described. The relative merits of satisfying boundary conditions by the use of a Lagrange multiplier or a perturbed (“penalty”) Lagrangian is discussed, as will the convergence properties with respect to grid refinement.
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Three‐dimensional finite‐element analysis of electroelastic normal modes of a tangentially polarized, segmented ferroelectric shell (A)

Harold A. Sabbagh and Thomas F. Krile

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S80-S80 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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We extend the variational method described in the preceding companion paper to calculate the short‐circuit and open‐circuit electroelastic normal modes of a tangentially polarized, segmented, ferroelectric shell. The basis functions used in the present variational approach are first‐order, three‐dimensional piecewise polynomials, whose method of generation is described. A discussion of the “condensation” scheme for satisfying boundary conditions is presented, and comments relevant to programming and numerical convergence matters are made.
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Analytical‐numerical method for the treatment of radiation from elastic structures I. General theory. II. Application to free‐flooded ring transducers (A)

M. A. Gonzalez and D. Barach

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S80-S80 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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Finite element methods have been used by several authors to study the problem of acoustical radiation from elastic structures [M.R. Knittel and D. Barach, Naval Undersea Center TP 412 (July 1974), and references contained therein]. The radiation loading of the structure due to the fluid medium can be taken into account either by numerical techniques based on the Helmholtz integral equation, or by additional finite element modeling of some of the liquid out to a separable surface where impedance conditions can be written in closed form. In this work we extend this method to the problem of radiation from multiple structures, either passive or active. Finite elements are used to model the scatterer and/or projector, as well as that portion of the liquid medium between the structure and a sphere completely surrounding it. The multiple‐radiation problem is then handled using the methods developed by Twersky and others for conventional boundary‐value problems [V. Twersky, “Scattering by Two Objects,” in Electromagnetic Waves, R.E. Langer, Ed., Univ. of Wisconsin P., Madison, WI (1962)]. As an application of the method we have analyzed the radiation from two tangentially polarized, ceramic free‐flooded rings. Directivity, source levels, and electrical impedance have been calculated for a range of frequencies. Comparison with experiment show very good agreement over the frequency band of interest.
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Exact solutions for the propagation of electric and acoustic waves in distributed coupling transducers (A)

Joseph F. Zalesak

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S80-S80 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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A distributed coupling transducer consists of an acoustic transmission line continuously and reversibly coupled to an electrical transmission line. In such a device it is possible to transfer almost all of the energy from one of the transmission lines to the other transmission line. In particular if the transmission lines are finite in length it is possible to achieve a high efficiency, nonresonant, broad‐band electroacoustic transducer. Some of the salient features of the exact solution are as follows: (1) the distance required to achieve complete energy transfer is significantly less than that predicted by approximate theory when the coupling coefficient is large; (2) the amount of energy transferred depends strongly on the termination impedance at the input end of the nondriven line; and (3) the input impedance of the driven line depends on the coupling coefficient and the termination impedance at the input end of the nondriven line. Some of the differences between a continuously coupled and a discretely coupled transducer are presented. [Work supported by NAVSEA 06H1.]
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Underwater Helmholtz resonator transducers (A)

R. S. Woollett

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S80-S80 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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Compact low‐frequency sound sources using piezoceramic drivers are feasible if the driver is incorporated into a Helmholtz resonator. The ceramic driver can be in the form of a spherical shell, a stack of rings, or a flexural‐mode disk, but the disk is usually the most advantageous. A liquid‐filled Helmholtz resonator transducer is capable of operation at unlimited depths. When the depth requirement is only moderate, however, it is advantageous to replace part of the liquid in the compliance chamber by compliant tubes; this substantially reduces the size of the resonator. The radiation resistance of these compact transducers is low and is usually considerably exceeded by the internal‐loss resistance of the resonator. For broad‐band applications the internal dissipation is not a significant disadvantage, since the resonance even when damped will give a very worthwhile bass boost to the low end of the transmitting response. For narrow‐band applications, where efficiency is important, careful consideration must be given to minimizing losses. Then the Q of the resonator may be on the order of 100. The resulting response peak would be too sharp to permit stable operation, but this problem can be overcome by use of acoustoelectrical feedback. The feedback flattens the response without negating the advantages of resonance with respect to efficiency and power. [Work supported by NAVSEA Sonar Technology Division.]
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Experimental investigation of shear waves in laboratory sediments (A)

D. J. Shirley and A. L. Anderson

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S80-S81 (1975); (2 pages)

Online Publication Date: 11 Aug 2005

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Transducers for the generation and detection of shear waves in solids have been developed. The transducers consist of arrays of ceramic bimorph bender elements arranged to propagate shear waves from the ends of the elements. The transducers have been used to measure shear‐wave speed and attenuation in laboratory mixed kaolinite clays and carbonate clays having shear moduli as low as 1.7×102 dyn/cm2. Shear‐wave speeds of 2 m/sec with attenuation of 496 dB/m have been measured over path lengths of 5 to 10 cm.
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Evaluation of transducer window materials (A)

E. Eugene Mikeska and John A. Behrens

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S81-S81 (1975); (1 page) | Cited 1 time

Online Publication Date: 11 Aug 2005

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Acoustic measurements of insertion loss and echo reduction at normal incidence were made for several materials for evaluation of their use as underwater sound transducer windows in the frequency range of 50–500 kHz. Materials tested included the commercial polyurethane products such as PR‐1527, CPC‐19, Scotchcast 221, Scotchcast 8, and some of these materials with talc added during curing to vary the density. Values of sound velocity are derived from the echo reduction data and allow determination of ρc values for each material. A computer model of the echo variation with frequency accurately matches the measured echo reduction plots.
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Development of a high‐power transducer DUMILOAD (A)

W. A. Miller and S. E. Auyer

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S81-S81 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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DUMILOAD (DUmmy Mechanical Impedance LOAD) devices have been used to test transducers for many years. In concept the DUMILOAD consists of another, specialized, piezoelectric transducer mechanically coupled to the transducer to be tested. By varying the electrical impedance placed across the DUMILOAD's electrical terminals, varying mechanical loads can be presented to the transducer being tested. Drawbacks to this approach have included the need for a cumbersome mechanical coupling device and the limited operating frequency band of the DUMILOAD. This paper describes some of the considerations involved in designing and constructing a DUMILOAD capable of operating at a power level of 1100 W in the frequency band from 3000 to 4000 Hz. Details of a “quick connect/disconnect” mechanical coupling device are also described.
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A deep‐ocean hydrophone array (A)

John A. Behrens and Robert H. Stokes

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S81-S81 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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A curved face hydrophone array has been designed, constructed, and tested for 20 000‐ft depth operations. A basic description of the hydrophone design is presented, where the hydrophone consists of a beamforming array of staves mounted on the circumference of a 20‐in.‐diameter cylindrical housing. Since conventional pressure release materials cannot be used in the construction, solutions to problems encountered, such as flexural waves generated in the housing wall and improper backing impedances for the individual elements, will be briefly discussed. A presentation of the received frequency response and beam patterns show that the transducer properties are insensitive to hydrostatic pressures up to 1000 psi.
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N‐port analysis of a projector consisting of a coaxial array of ferroelectric shells (A)

Thomas F. Krile and Harold A. Sabbagh

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S81-S81 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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The coupling between a coaxial array of six tangentially polarized, ferroelectric shells and the external fluid medium is analyzed by an application of N‐port theory. Properties of the lowest (“breathing”) mode of the shells are ascertained by using three‐dimensional finite elements, and this knowledge is utilized in defining an N‐port representation of the array. An N‐port representation of the external fluid is obtained by solving the Helmholtz integral equation that relates fluid velocity and pressure on the exterior of the array. The two N ports are coupled together in a standard circuit‐theoretic manner to produce an equation for the electrical driving‐point impedance of the loaded projector. Several frequency responses, which illustrate the effects of varying certain parameters, are presented.
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Shock wave revisited—a second look at some measurements of explosive acoustic source levels (A)

L. C. Maples

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S81-S81 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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Updated information on system characteristics and underwater explosive parameters and new theoretical/empirical models have provided new insights into measurements of source levels of small TNT charges at shallow and moderate depths. Preliminary results, for the shock wave from a 3‐lb charge of TNT, were presented at an earlier meeting of the Acoustical Society. In that paper, comparison with Weston's theoretical values showed differences of 2.5 to 5 dB. New evaluations of Weston's formulations, based on improved values of explosive parameters, show greatly improved comparisons and support measured values. Source levels for shock wave, bubble pulses, and entire wave train are presented for 3‐lb charges detonated at 60−, 500−, and 1000−ft depths and compared with measurements of Weston and Stockhausen and later values from Bell Laboratories, Naval Ordnance Laboratory, Sac Lant ASW Research Center and Defence Research Establishment, Atlantic. To complete the survey, values from models of Weston, Christian, Gaspin and Shuler, and NUSC are included.
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Analytical model of an explosive source (A)

R. B. Lauer, P. D. Herstein, and L. C. Maples

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S81-S81 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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An analytical expression, consisting of a series of transcendental functions, has been developed to simulate the waveform of an underwater explosive source. From this model the source spectrum may be calculated as function of charge weight and detonation depth. Energy flux density spectrum levels for 1.8‐lb TNT charges detonated at 60, 300, and 800 ft have been computed for ANSI 1/3‐octave bands in the range 10–1780 Hz. Comparison with results of a study by Gaspin and Shuler utilizing waveforms constructed from actual measurements of explosive parameters shows a mean difference of 0.6 dB and a standard deviation of 0.8 dB, above the bubble frequency. Agreement below this frequency is less satisfactory. The spectrum characteristics below the bubble frequency are not well understood but parameters associated with the first bubble pulse are shown to be important in this region. Preliminary studies of the sensitivity of the spectrum to changes in value of waveform parameters indicate the accuracies to which the magnitudes of various parameters must be known. Farther studies show the effects of small variations in detonation depth.
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Design of broad‐band transducer for high‐temperature application to nuclear reactors (A)

H. B. Karplus

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S81-S82 (1975); (2 pages)

Online Publication Date: 11 Aug 2005

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Ultrasonic transducers are usually damped with metal powder‐loaded plastic or lossy rubber materials, which are effective only over a narrow temperature region. A shear‐wave transducer was designed using only materials capable of withstanding high temperature (650 °C, 1200 °F). The design employs a laminated stainless steel coupling block, a piezoelectric X‐cut lithium niobate crystal, a laminated backing plate, and a clamp to force intimate mechanical contact between the crystal and the coupling block. Transmission of ultrasonic energy in the desired direction parallel to the interfaces of the coupling laminac is not affected by the laminated structure. However, subsequent reverberation in the coupling block is damped by Coulomb friction between interfaces after reflection at the third oblique surface of the coupling block. Radiation into the pressure pad forcing the crystal into contact with the coupling is strongly attenuated by laminating the pressure pad normal to the propagation direction. Uniformity of pressure is assured by applying pressure via a single ball bearing and thick solid blocks. The transducers were used to monitor flow in pipes by measuring sound velocity difference in the upstream and downstream directions. A time interval difference of 110 nsec for pulses transmitted simultaneously in both directions across a 4‐in. Schedule 10 stainless steel pipe (108.2 mm ID) was readily measured to four significant figures, using a HP model 5345 Time Interval Averager for water flow at 500 gpm (31.5 l/sec).
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Transmission of sound across dry metallic interfaces (A)

H. B. Karplus and M. Tupper

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S82-S82 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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Use of ultrasonic energy at high temperature, (e.g., in nuclear reactors) precludes conventional liquid coupling. Ultrasonic energy can be transmitted across dry interfaces if the surfaces are sufficiently flat and smooth, and static pressure is applied. Transmission and reflection coefficients were measured for shear waves polarized normal to the plane of incidence across lapped flat steel surfaces as a function of temperature, surface finish, and contact pressure. The transmission increases and reflection decreases monotonically with applied pressure. For example, at 20 °C, a contact pressure of 500 psi (3 MPa) produces 50% transmission across interfacing 304 stainless steel samples having measured surface finishes of 30μ in. (0.7μ m) and 70μ in. (2μ m), respectively. The contact pressure is reduced by using finer surface finishes and interposing soft metallic (e.g., Pt) shims.
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