Acoustic Radiation of Weakly Charged Droplets Oscillating in an External Uniform Electrostatic Field

The intensity of acoustic radiation of droplets and the width of the frequency range for which this radiation is accounted are evaluated in asymptotic calculations of the first order of smallness with respect to the dimensionless oscillation amplitude and equilibrium deformation of natural weakly charged droplets. The calculations are carried out using the ideal incompressible conducting fluid model. It is shown that acoustic radiation of fluid-droplet aerosol of natural origin, namely, clouds and fogs, is accounted for the ultrasonic frequency range, while acoustic radiation of rain occurs over the sonic range and such radiation can be hearable. The boundary between the ultrasonic and sonic acoustic radiations with respect to the droplet radius depends on the physical characteristics of the medium and the droplet and can be displaced both to one or another side.