Accession Number : AD0630326

Title :   ATTENUATION AND DISPERSION OF SOUND BY PARTICULATE RELAXATION PROCESSES.

Descriptive Note : Summary rept.,

Corporate Author : BROWN UNIV PROVIDENCE R I DIV OF ENGINEERING

Personal Author(s) : Temkin,Samuel

Report Date : FEB 1966

Pagination or Media Count : 37

Abstract : The temperature and velocity of a particle suspended in an acoustic field are subject to fluctuations which may lag behind those of the surrounding fluid. A theory for acoustic attenuation and dispersion in an aerosol based on these particulate relaxation processes is given. The close relationship between particulate relaxation and relaxation mechanisms due to lagging molecular or atomic internal degrees of freedom is displayed. The particulate relaxation theory predicts attenuation and dispersion by small, heavy particles in close agreement with existing, more detailed theories, for values of omega (tau omega = circular acoustic frequency, tau = dynamic relaxation time of the particle) smaller than and including order unity. Comparison with existing experimental data of attenuation and dispersion due to Zink and Delsasso shows good agreement. However, the existence of a maximum attenuation per wavelength, when omega tau nearly equal to 1, that is predicted by the theory is not tested by the above experiments which were conducted with omega tau > 1. Similarly, the maximum dispersion which occurs at the low frequency limit was not tested in the previous experiments. (Author)

Descriptors :   (*SOUND TRANSMISSION, AEROSOLS), (*AEROSOLS, SOUND TRANSMISSION), (*ACOUSTICS, AEROSOLS), RELAXATION TIME, ATTENUATION, SCATTERING, FLUID MECHANICS

Subject Categories : Acoustics
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE