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May 1990

Volume 87, Issue S1, pp. S1-S164

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back to top Session NN. Engineering Acoustics VI: Memorial Session for Ralph S. Woollett and Paul M. Kendig
Invited Papers
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Ralph Woollett and the art of transducer design at USNUSL (A)

Charles H. Sherman

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S93-S94 (1990); (2 pages)

Online Publication Date: 13 Aug 2005

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Ralph Woollett spent most of his life studying the subject of electroacoustics. He approached the subject with the attitude of a physicist, trying always to understand and to relate what he knew to basic physical laws. But he was also an engineer, analyzing the behavior of new transducer designs and creating new design concepts such as trilaminar flexural transducers and magnetostrictive drive of flexural bars. It was the good fortune of his colleagues that he also devoted much of his time to teaching them his way of looking at electroacoustics and suggesting interesting and relevant problems for them to work on. He was active in ASA and IEEE committees and was a U.S. delegate to the International Electrotechnical Commission's Subcommittee on Ultrasonics. Ralph's untimely, accidental death reminded us of a lesser known side of his personality, for he was an avid flyer and somewhat of an adventurer who was always seeking new experiences and challenges.
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Transducer longitudinal‐vibrator equivalent circuits and related topics (A)

Gordon E. Martin

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S94-S94 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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Ralph Woollett and this author began careers as Navy scientists in 1947. Advances in underwater electroacoustic transducers and their materials are described by illustrating lifetimes in parallel paths. Early activities of Woollett emphasized magnetostriction. In 1947, barium titanate ceramic ferroelectrics were introduced and began a revolution in transducer material technology. For transducer design and analysis, the esoteric theory is often interpreted in relation to equivalent circuits. Woollett used such equivalent circuits in transducer design and in the study of materials for transducer applications. The topic of longitudinal‐vibrator transducers and materials is described with reference to some of Woollett's works including his dissertation.
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A low‐frequency high‐power magnetic drive transducer (A)

William J. Marshall

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S94-S94 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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Ralph Woollett's contributions to the art and science of sonar transducer design were as a researcher, teacher, author, and reviewer. Of these roles, perhaps the most important, the one that became his legacy, was that of teacher: All of his colleagues were, in a sense, his pupils. His careful and thorough approach to transducer design problems inspired us to try to meet his high standards, and we still miss his insight, advice, encouragement, and criticism. This talk will review Ralph's influence on underwater electroacoustics, present some anecdotes about his life and work, and examine the circumstances of his death. Finally, it will show how Ralph's ideas and design philosophy have affected some of the author's present research, specifically the design of a low‐frequency high‐power magnetic drive transducer having low distortion.
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The development of low‐frequency trilaminar bender bar transducers (A)

Manuel A. Gonzalez

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S94-S94 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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Acoustic underwater projectors using bender bar technology are widely used as sound sources in low‐frequency sonar applications. In the early 1980's, the Marine Systems Division of Honeywell in Everett, Washington, under contract with NUSC, initiated a development program to dramatically improve the acoustic performance and reliability of low‐frequency bender bar projectors for a submarine sonar application. This contract provided the vehicle for an extremely fruitful interaction with Ralph Woollett, and resulted in the development of the trilaminar bender bar concept now used in the new family of high‐power, high‐efficiency, bender bar transducers built by Honeywell over the past few years. Ralph made significant contributions to our theoretical understanding and modeling of these transducers. He also set a personal example of technical excellence and integrity that motivated all of us who were involved with him in this project. In this paper, the theory of operation of trilaminar bender bars will be summarized, the major performance benefits that they offer will be presented, and some recent work in the low‐frequency transduction area will be described.
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Paul Kendig: Acoustician and teacher (A)

Eric A. Walker

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S94-S94 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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A professional account and personal observations of Paul Kendig's accomplishments and contributions to the field of acoustics.
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Paul Kendig and directional response control for planar acoustic arrays (A)

Geoffrey L. Wilson

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S95-S95 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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Paul Kendig was a pioneer in the application of techniques developed by the radar community for line arrays to the control of sidelobe response from the planar arrays used in sonar. The magnetostrictive “hair‐pin” transducer element developed at the Harvard Underwater Sound Laboratory and at Penn State's Ordnance Research Laboratory lent itself easily to such control merely by adjusting the number of turns on the coils. This paper discusses briefly the development of the theory, and its application to these magnetostrictive arrays and to the piezoceramic arrays that were being developed in the early 1960s.
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Paul M. Kendig—The ARL years 1966–1971 (A)

William Thompson, Jr.

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S95-S95 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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The leadership that Paul Kendig provided to the research efforts of the Transducer Group of the Applied Research Laboratory, Penn State University, during the indicated years is reviewed and fondly remembered, as well as his own technical contributions. The thrust of this work was on improving the design and construction of Tonpilz transducer elements and arrays, achieving directivity patterns with very low sidelobes, obtaining multiple, tilted, directivity patterns, bringing on line a new sonar transducer calibration facility, developing other experimental transducers, and guiding a variety of graduate thesis research topics.
Contributed Papers
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Characterization of Terfenol‐D for magnetostrictive transducers (A)

Mark B. Moffett, Arthur E. Clark, Marilyn Wun‐Fogle, Jan F. Lindberg, Joseph P. Teter, and Elizabeth A. McLaughlin

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S95-S95 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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Measurements were made of the piezomagnetic d33 coefficient, the free permeability, math33T, and the open‐circuit elastic compliance coefficient, s3311, of grain‐oriented Terfenol‐D, Tb0.3 Dy0.7 Fe1.93, produced by a modified Bridgman technique. Prestress levels to 9500 psi (64 MPa) and magnetic bias fields up to 2200 Oe (175 kA/m) were applied with a laboratory electromagnet modified so that one pole piece served as a hydraulically actuated piston. The results indicate that d33,math33T, and s3311 are dependent on stress and magnetic field, so that proper mechanical prestress and magnetic bias conditions are critical to the successful use of Terfenol‐D in transducers and actuators. Radiated‐power limits for underwater acoustic projectors are estimated and compared with those for projectors having lead zirconate titanate (PZT‐4) piezoelectric drivers. Terfenol‐D based transducers can be as much as 8 dB superior to PZT‐4 under low‐Q, field‐limited conditions (Q = mechanical quality factor). Terfenol‐D is not superior to PZT under high‐Q, stress‐limited conditions.
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Low‐frequency hydrophone calibration (A)

Mark E. Geleskie and W. Jack Hughes

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S95-S95 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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Low‐frequency underwater acoustic calibration of hydrophones in finite semireverberant tanks has always been desired. However, for a given tank, the physical dimensions determine the lowest frequency measurement possible using standard short‐pulse calibrations. A long‐pulse technique has been used to extend calibrations from the short pulse limit of 5 kHz down to 1–2 kHz. It is known that if the acoustic impedance of a transducer is high enough so that its radiation impedance can be neglected (such as at very low frequencies) and if the transducer is also small enough so that diffraction effects can be neglected, then the transducer's receiving sensitivity will be the same in air as it is in water. This property is used to verify the accuracy of calibrations made in an acoustic tank at low audio frequencies using both the traditional short‐pulse calibration method and the long‐pulse technique. This paper compares the air and water calibrations of hydrophones, showing the validity of the long‐pulse method and the agreement with the short‐pulse measurement technique.
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Nearfield calibration array for hydrophones and arrays (A)

Philip A. Ferlino and W. Jack Hughes

J. Acoust. Soc. Am. Volume 87, Issue S1, pp. S95-S95 (1990); (1 page)

Online Publication Date: 13 Aug 2005

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A plane‐wave volume was synthesized with a line array of projectors in a 7‐ to 50‐kHz frequency range enabling hydrophones and hydrophone arrays to be calibrated in the nearfield. The plane‐wave volume was created using the Van Buren technique by revolving a suspended line of PZT‐4 type transducers in a semicircular fashion. Results were compared with the known sensitivities and directivity patterns of the hydrophones used. Amplitude shading coefficients for the line array were determined by a computer program furnished by A. L. Van Buren [Underwater Sound Reference Detachment, Naval Research Laboratory].
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