Measurements of particulate acoustic attenuation

Important implications of the theory of the attenuation of sound by suspended particles to the stabilization of solid propellant combustion are discussed An experimental 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 is described Acoustic attenuation by an aerosol composed of oleic acid particles of controlled size and concentration is measured in an acoustic impedance tube Mean particle size and concentration are measured by optical 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 a source of acoustic attenuation decreases at small dimensionless sizes The present data combined with the previous data due to Zink and Delsasso confirm the existence of an optimum particle size to attenuate sound waves of a given frequency