Friday, December 5, 1986 12:00 p.m. David Grant Applied Research Laboratories The University of Texas at Austin The spatial structure of the acoustic signal field near the ocean bottom was investigated experimentally. A source near the ocean surface projected a CW tone as it moved along a radial path from a range of 40 km…
Friday, November 21, 1986 12:00 p.m. Ethan Vishniac Astronomy Department The University of Texas at Austin The interstellar medium is constantly subjected to explosive accelerations from a variety of events ranging from stellar winds to supernovae. The kinetic energy imparted to the gas acts to counteract the gravitational force and modulates the rate of star…
Friday, October 31, 1986 12:00 p.m. Terry L. Foreman Applied Research Laboratories The University of Texas at Austin Geometrical ray theory has proven to be a versatile and popular method for obtaining approximate solutions to the Helmholtz equation ∇2Ψ+k2Ψ=0 in such diverse fields as optics and underwater acoustics. But ray theory suffers from several deficiencies,…
Friday, 24 October 1986 12:00 p.m. Aerodynamic Generation of Sound, The Movie (44 minutes) directed and produced by Sir James Lighthill and J.E. Ffowcs Williams for the US Committee for Fluid Mechanics Films The study of sound produced by a variety of sources usually requires the use of well-calibrated microphones, accelerometers, and anechoic chambers. However,…
Friday, 17 October 1986 12:00 p.m. Stephen Schreppler Applied Research Laboratories The University of Texas at Austin When an electrical current passes through a resistive fluid in the presence of a magnetic field, two mechanisms for sound generation are present. The interaction of the electrical current with the magnetic field results in the Lorentz force…
Wednesday, October 8, 1986 4:00 p.m. Dr. Mark Hamilton The Department Mechanical Engineering The University of Texas of Austin A discussion of the role of acoustics in mechanical systems. Among the novel applications of acoustics are levitation, heat engines, particulate control, and microscopy. Special attention will be devoted to current research at UT in nonlinear…
Wednesday, April 23, 1986 4:00 p.m. John Sample Applied Research Laboratories The University of Texas at Austin Since it is relatively easy to integrate gaussian functions, it is tempting in certain cases to model complex sound sources as a superposition of gaussian functions. One such case is in the calculation of the parametric radiation associated…
Wednesday, April 16, 1986 4:00 p.m. Christopher L. Morfey The Institute of Sound and Vibration Southampton, England This tutorial lecture will look at the way modes are used to describe the linear acoustic response of ducts and rooms to sources of sound. Beginning with the unforced situation, first the propagation of duct modes (with respect…
Wednesday, April 9, 1986 4:00 p.m. Timothy S. Hart Department of Electrical Engineering The University of Texas at Austin The nonlinear behavior of focused sound beams is not completely understood. Past research has failed to examine situations in which the effects of both nonlinearity and diffraction are strong. Our technique involves the numerical solution of…
Wednesday, April 2, 1986 4:00 p.m. Craig Wier Speech Communications The University of Texas at Austin Improved micro-manipulation techniques are revealing important new information about transduction mechanisms in hair cells. Following a brief review of the fundamentals of auditory-system anatomy, physiology and biophysics, the results of recent work on hair-cell behavior will be described.
Wednesday, March 19, 1986 4:00 p.m. Robert A. Koch Applied Research Laboratories The University of Texas at Austin Practical applications of imaging (beamforming) techniques for inhomogeneous media require an assessment of the constraints imposed by the propagation environment. In this seminar the general features of such constraints will be illustrated with results for an ocean…
Wednesday, March 12, 1986 4:00 p.m. Gary R. Wilson Applied Research Laboratories The University of Texas at Austin Although spectral analysis of time series is a useful tool in many areas, it has generally been limited to the power spectrum. The less commonly employed higher-order spectra (polyspectra) contain information about the time series that cannot…
Wednesday, March 5, 1986 4:00 p.m. Paul J . Vidmar Applied Research Laboratories The University of Texas at Austin Typical marine sediments are rigid enough to sustain the propagation of shear waves. Reviewed in this seminar is the influence of shear wave coupling on the plane wave reflection coefficient of the seafloor. The following mechanisms…
Wednesday, February 26, 1986 4:00 p.m. Jack Evans Joiner-Rose Group, Inc. There are two general classes of noise: loud and louder. Most engineers, architects, and faculty managers will encounter noise at some time in their careers. It is important to realize that most noise can be controlled by paying close attention to basic building and…
Wednesday, February 19, 1986 4:00 p.m. James A. Hawkins, Jr. Applied Research Laboratories The University of Texas at Austin With the advent of large megawatt sized wind turbines has come an interest in the low frequency noise from the turbines . NASA has reported measurements of downwind propagation for very low frequency noise from a…
Wednesday, February 12, 1986 4:00 p.m. David McCandless, Jr. The Joiner-Rose Group, Inc. Looking back over almost 30 years of consulting in Architectural acoustics conjures up some insights to share and some questions to ask. Is acoustics an art or a science? How much does the jargon of acoustics confuse discussions of it? How do…
Wednesday, February 5, 1986 4:00 p.m. T.L.Henderson Applied Research Laboratories The University of Texas at Austin A narrowband approach to signal subspace processing of acoustical signals has been developed over the past several years. Recently, a broadband approach has been developed, requiring the use of dense arrays of hydrophones. Applications will be discussed, for example,…
Wednesday, January 29, 1986 4:00 p.m. David Knobles Applied Research Laboratories The University of Texas at Austin The mathematical aspects of applying classical ray theory to describe acoustic interaction with the seafloor are developed. An integral solution of the time independent wave equation for a point source is first developed. Stationary phase approximations are made…
Thursday, December 5, 1985 3:30 p.m. C. T. Tindle Applied Research Laboratories on leave from University of Auckland Auckland, New Zealand Exact theoretical descriptions of acoustic propagation in shallow water are restricted to horizontally stratified situations. There are no exact descriptions for propagation over a sloping bottom. Experimental measurements have been made in an indoor…
Thursday , November 14 , 1985 3:30 p.m. Corinne Darvennes Department of Mechanical Engineering The University of Texas at Austin Many noise control problems remain unsolved because the values of the speed of sound in real gases are lacking. In the low pressure limit, the perfect gas approximation can be used. At higher pressures, a good estimate…