Accession Number : ADA183407

Title :   Optical Sound Generation and Amplification.

Descriptive Note : Summary rept. 1 Jan 84-31 Dec 86,

Corporate Author : MISSISSIPPI UNIV UNIVERSITY PHYSICAL ACOUSTICS RESEARCH LAB

Personal Author(s) : Bass,Henry E ; Shields,F D

PDF Url : ADA183407

Report Date : 27 Feb 1987

Pagination or Media Count : 14

Abstract : This research has concentrated on sound propagation through a gas with a nonequilibrium distribution of internal states and the generation of sound following excitation of a fluid by a laser. When a sound wave propagates through a gas which has an overpopulation of vibrationally excited states, the wave can increase in amplitude while propagating. In simple terms, this represents a reversal of the absorption typically associated with vibrational relaxation. Amplification of a propagating wave has been theoretically predicted and experimentally observed for a gas undergoing chemical reaction and following an electrical discharge through a non-reacting mixture. Optoacoustic measurements have been completed in gaseous CO 2 and SF 6 and preliminary results are reported for several liquids. Following laser excitation of SF 6 at low pressure, the gas actually cooled. A theoretical model for this behavior consistent with known energy transfer mechanisms has been developed and shown to be consistent with experiment measurements.

Descriptors :   *ACOUSTOOPTICS, *AUDIO AMPLIFIERS, *LASER PUMPING, *SOUND GENERATORS, CARBON DIOXIDE, MOLECULAR VIBRATION, ABSORPTION, CHEMICAL REACTIONS, DISTRIBUTION, ELECTRIC DISCHARGES, ENERGY TRANSFER, EXCITATION, MEASUREMENT, MODELS, NONEQUILIBRIUM FLOW, OPTICAL PROPERTIES, RELAXATION, REVERSIBLE, SOUND, SOUND TRANSMISSION, SOUND WAVES, THEORY, VIBRATION, WAVE PROPAGATION

Subject Categories : Acoustooptic and Optoacoustic Devices
      Acoustics
      Lasers and Masers

Distribution Statement : APPROVED FOR PUBLIC RELEASE