Wednesday, April 26, 1989 4:00 p.m. Michalakis A. Averkiou Department of Mechanical Engineering The University of Texas at Austin Target geometry and orientation significantly affect the current accuracy of high precision ultrasonic proximity sensors. The reflection of focused sound (that is generated by a source with either a uniform or Gaussian distribution) from curved, rigid…
Wednesday, April 19, 1989 4:00 p.m. Edel Reiso Department of Mathematics University of Bergen and Department of Mechanical Engineering The University of Texas at Austin The propagation of finite amplitude sound waves produced by real sources in an in homogeneous and thermoviscous fluid is considered. A nonlinear parabolic equation in the normalized sound pressure amplitude…
Wednesday, April 12, 1989 4:00 p.m. Chuck Bradley Department of Mechanical Engineering The University of Texas at Austin Linear wave propagation in periodically inhomogeneous media is characterized by the division of the frequency spectrum into regions known as passbands and stop bands, the waves associated with which are propagated and attenuated, respectively. Other unusual phenomena…
Wednesday, April 5, 1989 4:00 p.m. Dominique Laget Department of Electrical Engineering The University of Texas at Austin Noise attenuation can be obtained by superposition of two noises. Active noise control uses a secondary source to perform this superposition. This method can be more successful than passive cancelers when the frequency of the noise is…
Monday, March 27, 1989 4:00 p.m. Kimitoshi Fukudome Department of Acoustic Design Kyushu Institute of Design Fukuoka, Japan This paper describes a method for the three-dimensional reproduction of any constituent sound signals existing in the interfering sound field. The method is composed of three parts. (1) Estimation of incident directions and spectra of unknown sound…
Wednesday, March 22, 1989 4:00 p.m. Jim Fox Department of Psychology The University of Texas at Austin A hypothesis is examined that male frogs and toads form choruses so as to derive certain acoustic advantages resulting from call overlap. Computer models of hypothetical choruses demonstrate that chorusing may result in the augmentation of per capita…
Wednesday, March 8, 1989 4:00 p.m. J. A. Hawkins and Dr. A. Bedford Department of Engineering Mechanics The University of Texas at Austin Bubbles of gas occur naturally in a layer near the ocean surface and in ships’ wakes. Well established continuum theories exist for the propagation of acoustic waves through a bubbly liquid when…
Wednesday, March 1, 1989 4:00 p.m. Professor A. Bedford and J. A . Hawkins Department of Engineering Mechanics The University of Texas at Austin Gas bubbles in a liquid greatly alter the acoustic properties (both velocity and attenuation) of the liquid. This talk is a prologue to a seminar on the development of a theory…
Wednesday, February 22, 1989 4:00 p.m. Dr. Wayne Wright Physics Department Kalamazoo College Kalamazoo, Michigan Department of Mechanical Engineering and Applied Research Laboratories The University of Texas at Austin One of the best known predictions of nonlinear acoustics deals with propagation distortion of plane waves. An initially sinusoidal wave, for example, is expected to distort…
Wednesday, February 8, 1989 4:00 p.m. Chris Kenny Department of Mechanical Engineering The University of Texas at Austin Piezoelectric crystals are commonly used for acoustic range finding. The crystal is oscillated to create a tone burst, turned off, and when the echo comes back the crystal is also used to receive the echo. The crystal…
Wednesday, February 1, 1989 4:00 p.m. Professor Elmer Hixson Department of Electrical Engineering The University of Texas at Austin A brief history of acoustic signaling from the bottom of an oil well will be presented. Then the transmission characteristics of stress waves in pipe with discontinuities every 30 ft (tool joints) is shown to consist…
Wednesday, January 25, 1989 4:00 p.m. Professor David T. Blackstock Department of Mechanical Engineering and Applied Research Laboratories The University of Texas at Austin An electric spark produces an intense acoustic pulse, which is called an N wave because its waveform resembles the letter N. An experiment is described in which both spark and receiver…
Wednesday, December 7, 1988 1:00 p.m. Dr. Linda M. Thibodeau Department of Speech Communication The University of Texas at Austin The enhancement effect is the increased audibility of a target component in a harmonic series by prior exposure to the series with the target component deleted. One explanation for this effect involves the adaptation of…
Wednesday, November 9, 1988 12:30-2:00 p.m. “Nonlinearity in Sound Beams with Application to the Scattering of Sound by Sound” by Jacqueline Naze Tjøtta and Sigve Tjøtta “Self Calibrating Apparatus for the Measurement of Dynamic Compressibility” by Dave Edmonds “A Parametric Array for Use as an Ultrasonic Proximity Sensor” by Yang-Sub Lee “Complex Ray Methods for…
Wednesday, November 2, 1988 1:00 p.m. Yang-Sub Lee Department of Mechanical Engineering The University of Texas at Austin Ultrasonic proximity sensors are used in robotics and other industrial processes to locate objects in air without direct physical contact. We investigate the possibility of using an ultrasonic proximity sensor employing a parametric array as an alternative…
Wednesday, October 26, 1988 1:00 p.m. Dr. V.N. Bindal National Physics Laboratory New Delhi, India Dr. Bindal is Deputy Director and head of the Materials Division of National Physics Laboratory in New Delhi, India. His current works involve underwater acoustics, Ultrasonic Nondestructive Testing, medical ultrasonics, Ultrasonic Standards, and Ceramic Transducer Materials.
Friday, October 21, 1988 1:00 p.m. Jeff McAteer AT&T Consumer Products Lab and Department of Mechanical Engineering The University of Texas at Austin A broadside linear array microphone having near constant beamwidth and improved directivity over 300 to 3300 Hz frequency range is presented. The system consists of three collinear, 3-element arrays, but because of…
Wednesday, October 19, 1988 1:00 p.m. Oscar M. Weaver, Jr. M.D. Medical Imaging Department Perry County Memorial Hospital Tell City, Indiana A short introduction to the clinical applications of diagnostic ultrasound will be provided , followed by a number of actual case presentations using the images physicians place at their disposal in clinical practice. Sales…
Monday, October 10, 1988 1:00 p.m. Akira Nakamura Oska University Oska, Japan As is well known, the nonlinear distortion of finite amplitude sound results from the fact that propagation speed depends on particle velocity and the nonlinearity parameter of the medium. In the case of a thin fiber of fused silica, the waveform of a…
Wednesday, October 5, 1988 1:00 p.m. Jack Leifer Department of Mechanical Engineering The University of Texas at Austin An acoustical system is being developed for use as a highly accurate positioning device in robotics applications. The system includes a high frequency, omnidirectional ultrasonic source, and a number of PVDF based pick-up microphones. This seminar will…