Wednesday, December 9, 1987 12:00 p.m. Dean Driebe Physics Department and Applied Research Laboratories The University of Texas at Austin Some of the interesting nonlinear phenomena exhibited by focused finite-amplitude sound beams will be discussed. Linear, low-amplitude focusing will be reviewed with emphasis on a solution convenient to use in a quasilinear analysis. A parabolic…
Wednesday, December 2, 1987 12:00 p.m. Dr. Elmer L. Hixson Department of Electrical and Computer Engineering The University of Texas at Austin A brief travelogue and description of the immersion into Japanese and Chinese culture of a traumatized Texas couple, including looks at Acoustic Activity, will be presented. An overview of INTER-NOISE 87, September 14-17,…
Wednesday, November 25, 1987 12:00 p.m. Kevin P. Flynn Department of Mechanical Engineering The University of Texas at Austin Experiments have been conducted to determine the interaction that occurs between resonators when excited by grazing flow. The orifices of ten cylindrical Helmholtz resonators were flush mounted across the span of a wind tunnel wall. Resonator…
Wednesday, November 11, 1987 12:00 p.m. Dr. Noel J. Walkington Department of Mathematics The University of Texas at Austin The theme of my seminar will be the calculation of the forward sound field around high by-pass ratio turbofan aircraft engines. These engines have large fans at the front which “chop” the inducted air, producing a…
Wednesday, November 4, 1987 12:00 p.m. Professor Dennis Wilson Department of Mechanical Engineering The University of Texas at Austin The results of a theoretical investigation into the effects of finite amplitude acoustic disturbances or weak compression and expansion waves on compressible boundary layers will be discussed. These pressure disturbances, which are produced by combustion instabilities,…
Friday, October 30, 1987 12:00 p.m. Dr. Philippe Blanc-Benon Centre Acoustique Ecole Centrale de Lyon Ecully, France Two specific investigations will be presented for the propagation of acoustic waves through velocity or temperature fluctuations in well-controlled laboratory conditions (2-D jet used along its span-wise direction or thermal plumes rising above a large heated grid). The…
Wednesday, October 21, 1987 12:00 p.m. Dr. Jacqueline Naze Tjøtta and Dr. Sigve Tjøtta Department of Applied Mathematics University of Bergen Bergen, Norway and Applied Research Laboratories The University of Texas at Austin The reflection and transmission of a real sound beam at the interface between two homogeneous and dissipative fluid layers is considered. Numerical…
Wednesday, October 14, 1987 12:00 p.m. Steve Lind Department of Mechanical Engineering The University of Texas at Austin The noncollinear interaction of a tone with noise is investigated experimentally in an air-filled rectangular duct. A low frequency band of noise in the (0,0) mode interacts with a high frequency pure tone in the (1,0) mode.…
Wednesday, October 7, 1987 12:00 p.m. Professor Dennis McFadden Department of Psychology The University of Texas at Austin For about two decades we have known for certain that the peripheral auditory system does accurately encode information about the temporal periodicity of the acoustic waveform. Long before (and since) that demonstration, auditory theorists had appealed to…
Wednesday, September 30, 1987 12:00 p.m. Dr. Terry L. Foreman Applied Research Laboratories The University of Texas at Austin Practical computational procedures for obtaining ray theoretical solutions to the inhomogeneous Helmholtz equation ∇Ψ + k2Ψ = S(r,ω) make resort to a well-known approximation. A computational method is presented which enables one to trace rays without…
Wednesday, September 23, 1987 12:00 p.m. Professor Ching H. Yew and X. Weng Department of Aerospace Engineering and Engineering Mechanics The University of Texas at Austin The sea ice is modeled as a transversely isotropic brine saturated porous medium in accordance with the model proposed by Schwarz and Weeks [1977]. The reflection and refraction of…
Wednesday, September 16, 1987 12:00 p.m. Professor Wayne M. Wright Kalamazoo College Kalamazoo, Michigan For about 20 years the Acoustical Society of America has been carrying out a variety of programs in environmental acoustics, including community education to inform lay public about problems in noise and noise control, consulting with city councils, state legislatures, and…
Wednesday, September 9, 1987 12:00 p.m. David T. Blackstock Department of Mechanical Engineering and Applied Research Laboratories The University of Texas at Austin Lithotripsy is a medical procedure by which focused shock waves are used to break up kidney stones. In the most commonly used lithotripter, the shock is generated by an electric spark at…
Wednesday, May 6, 1987 1:00 p.m. Luis J. Gonzalez The University of Texas at Austin The generation of underwater sound by a moving high power laser pulse is numerically investigated. The acoustic wave is induced by thermal expansion of the water caused by heat imparted by the laser. The numerical predictions are based on a…
Wednesday, April 29, 1987 1:00 p.m. Deborah A. Summa Department of Mechanical Engineering The University of Texas at Austin Active vibration control techniques to date apply point sensors and actuators to continuous systems. Such techniques, while adequate, require excessive signal conditioning and involve approximations which often result in modal truncation. Continuous film transducers allow the…
Wednesday, April 22, 1987 1:00 p.m. Timothy S. Hart The University of Texas at Austin Past research into the behavior of focused sound beams has failed to account for situations in which the effects of both nonlinearity and diffraction are strong. A numerical solution of a parabolic, nonlinear wave equation that accounts for nonlinearity, diffraction…
Wednesday, April 1, 1987 1:00 p.m. Nicholas P. Chotiros Applied Research Laboratories The University of Texas at Austin The interaction of a short high intensity laser pulse with the surface of water is investigated. The reaction is similar to an explosion. The process of sound generation is modeled as an impulse response problem. Experimental observations…
Wednesday, March 25, 1987 1:00 p.m. Milo M. Backus Dave P. Carlton Professor of Geophysics The University of Texas at Austin Some examples of “conventional” seismic imagery will be shown. (1) A regional deep sea line recorded by the research vessel U.T. Fred Moore illustrates the full sedimentary column and oceanic basement, and a reflecting…
Wednesday, March 11, 1987 1:00 p.m. Richard E. Boner Boner Associates, Inc. Consultants in Acoustics and Communications The First Presbyterian Church is a Gothic structure constructed circa 1920. During its first 65 years, it developed a reputation of mediocre acoustics for speech and for various forms of music. A study was undertaken to develop recommended…
Wednesday, March 4, 1987 1:00 p.m. J. D. Sample Applied Research Laboratories Nearfield effects stand in the way of using parametric arrays to accurately measure the acoustic directivity of noise sources in multipath environments. Understanding these effects may lead to a technique of compensating for or eliminating them. Using the theory developed by M. F.…