Abstract Early theories of acoustic propagation such as those by Urick, and Urick and Ament, are attractive because of their computational simplicity, but limited in application. The more complex models of Allegra and Hawley, and Harker and Temple, have since gained application. A wideband ultrasonic attenuation and phase velocity spectrometer have been used to determine the validity of these models for a range of colloidal materials. Measurements taken validate the Allegra and Hawley model for colloids with spherical base particles. The Harker and Temple model is used to infer changes in the flocculation state of kaolin slurries which result from chemical intervention.