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.

Report Date:

1987-02-27

Pagination or Media Count:

14.0

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