This document specifies requirements for ultrasonic attenuation spectroscopy methods for determining the size distributions of a particulate phase dispersed in a liquid at dilute concentrations, where the ultrasonic attenuation spectrum is a linear function of the particle volume fraction. In this regime particle-particle interactions are negligible. Colloids, dilute dispersions, and emulsions are within the scope of this document. The typical particle size for such analysis ranges from 10 nm to 3 mm, although particles outside this range have also been successfully measured. For solid particles in suspension, size measurements can be made at concentrations typically ranging from 0,1 % by volume up to 5 % by volume, depending on the density contrast between the solid and liquid phases, the particle size, and the frequency range^[9],^[10]. For emulsions, measurements can be made at much higher concentrations. These ultrasonic methods can be used to monitor dynamic changes in the size distribution.