Constitutive models for the vibroacoustics of porous materials have previously been defined for lattice cell, foam and fibrous materials in terms of dynamic viscous drag forces and oscillatory solid to fluid heat transfer effects. Where the microgeometries are cylindrical in nature, analytical expressions have been derived to efficiently represent the viscous and thermal effects. A logical extension of this work is towards porous materials consisting of spherical shapes, which may also be defined using analytical relations. In this work, the analytical dynamic viscous drag force and oscillatory thermal impedance expressions of a sphere undergoing rectilinear oscillations in a viscous fluid are derived. A transfer matrix model of acoustic wave propagation is then used to predict the sound absorption performance of an array of packed spheres, using only the porosity and mean diameters of the spheres, and the constitutive properties of the solid spheres and the surrounding viscous fluid as modelling inputs. The results compare very well with published measurements.