The change of ultrasound velocity in aqueous solution was investigated as a function of particle size and suspension density. NaCl, KNO3, K2SO4 and MgSO(4)(*)7H(2)O was used as model substances. Measurements were made on a series of suspensions with different solid concentration (from 0-60%wt) and particle sizes ranges (from 250-500 mum). It was found that there is a strong relation between the particle size and/or suspension density and the ultrasonic velocity. This relation was correlated with a second degree polynomial equation and the error percent was determined. Also the compressibility of the media and particles were calculated based on Urick equation. (C) 2002 Elsevier Science B.V. All rights reserved.