Accession Number : AD0602245

Title :   MEASUREMENTS OF THE ATTENUATION OF SOUND BY SUSPENDED PARTICLES,

Corporate Author : BROWN UNIV PROVIDENCE R I

Personal Author(s) : Dobbins,R. A. ; Temkin,S.

Report Date : MAR 1964

Pagination or Media Count : 54

Abstract : The addition of metallic species to a propellant formulation frequently results in the suppression of combustion instability. The attenuation of acoustic waves by suspended particles is one stabilizing influence present when such a modification is made to the propellant composition. The work is an experi mental study of the attenuation of acoustic waves by suspended particles with emphasis on dimensionless size range of greatest interest in the study of rocket instability. An aerosol composed of oleic acid particles of controlled size and concentration is produced in a La Mer generator. Attenuation of sound by the aerosol is measured by means of an acoustic impedance tube similar to those used to measure properites of acoustic insulating materials. Mean particle size and concentration are measured by transmission and sampling tests of the aerosol in situ. Results of measurements made to date indicate fair agreement with theory and show that the efficiency of the particles as acoustic attenuators decreases at small dimensionless sizes. The data confirm the existence of an optimum particle size to attenuate sound waves of a given frequency. (Author)

Descriptors :   (*SOLID ROCKET PROPELLANTS, COMBUSTION), (*SOUND, ATTENUATION), (*AEROSOLS, FUEL ADDITIVES), ROCKET PROPELLANTS, STABILITY, PARTICLES, OLEIC ACID, PARTICLE SIZE, AEROSOL GENERATORS, ACOUSTIC IMPEDANCE

Distribution Statement : APPROVED FOR PUBLIC RELEASE