Recent applications of ultrasound in the characterization of colloidal suspensions have brought acoustophoresis to the attention of many colloid scientists. Analysis of the friction force experienced by an isolated sphere oscillating in an infinite body of viscous fluid has been presented by Stokes. Recently, the free surface cell model was extended to account for hydrodymanic interactions in multiparticle systems subjected to oscillatory motion. This paper deals with the oscillating sphere-in-model results for complex friction factor as a function of oscillatory Reynold's number and particle volume fraction. Magnitude and phase shift of acoustophoretic velocity is expressed in terms of the complex friction factor. Measurable colloid vibration potential and excess attenuation coefficient are related to the acoustophoretic velocity.