Accession Number : ADA017372

Title :   Experimental Investigation of the Laser-Excited Thermoacoustic Array in Water.

Descriptive Note : Final rept. 1 Apr 73-31 Dec 74,


Personal Author(s) : Culbertson,C. Robert

Report Date : 23 SEP 1975

Pagination or Media Count : 73

Abstract : An experimental evaluation of the Westervelt-Larson theory for the pressure and directivity of the laser-excited thermoacoustic array in water has been conducted. Instrumentation includes a modulated laser system that operates at 0.6943 micrometer and 1.06 micrometers, with a modulated frequency range of 5 to 80 kHz. Apparatus and methods for measuring the attenuation of light in water at the optical wavelengths of interest have also been implemented. An existence test confirmed that an acoustic signal is produced by thermalization of modulated laser light in lake water. The sound is generated in a beam with a measured half-power angle theta that is in reasonable agreement with theoretical prediction. The source level is a linear function of laser output power and measured absolute values of source level are in good agreement with theory. It may be concluded that the Westervelt-Larson theory is a valid model for predicting the pressure and directivity of the laser-excited thermoacoustic array in water.

Descriptors :   *Acoustic arrays, *Laser beams, Sonar arrays, Light transmission, Ruby lasers, Neodymium lasers, Thermal expansion, Heating, Sound transmission, Frequency modulation, Instrumentation, Mathematical models, Nonlinear systems, Theses, Green's function, FORTRAN

Subject Categories : Acoustic Detection and Detectors

Distribution Statement : APPROVED FOR PUBLIC RELEASE