Design of Spherical Aerosol Particles to Maximize Sound Attenuation

Analytic expressions for the audible sound absorption and scatter cross sections of an aerosol consisting of spherical particles are identified. The acoustic cross sections per aerosol mass and volume are explored as functions of three independent variables (sound frequency, particle diameter, and particle density) to determine regions of strong attenuation of audible sound. Optimum diameters, and densities that maximize cross sections per mass and volume at specific frequencies are found by reading contour plots contained in the figures of this report. Corresponding expected levels of acoustic attenuation are also contemplated. To a small extent, it is possible to scatter audible acoustic radiation with aerosol particles while aerosol absorption of sound can be significant. Comparing the levels of audible sound attenuation by atmospheric gases plus water vapor with the levels of attenuation achievable with an aerosol, we find that aerosol absorption of sound can greatly exceed that of the intervening air. Particle design, Aerosol, Acoustic cross sections, Sound attenuation, Acoustic scatter, Acoustic absorption