Acoustic sand monitors are used in the petroleum industry to detect the amount of sand moving through a pipeline. Currently there is no unified model to relate the sand monitor output to sand rate. An experimental program was implemented to determine the effects of superficial gas velocity, superficial liquid velocity, sand particle size and viscosity on sand monitor output. By examining the way in which the sand monitor operates a model relating sand monitor output to particle impact kinetic energy and sand rate was developed. This model is shown to accurately predict the trends seen in the experimental data.