Ultrasonic attenuation spectroscopy is a recently developed technique for rapid characterisation of particulate suspensions at high concentrations. Implementation of the full Epstein - Carhart -Allegra -Hawley model, which is used to transform ultrasound attenuation measurements into particle size and concentration information, requires knowledge of seven physical properties of the particulate phase and of a further seven properties of the continuous phase. Reliable data are not always available for all these properties. In this study, an assessment is made of the influence of inaccuracy in the physical properties on the recovered values of particle size and concentration.Two systems of organic crystals, glutamic acid crystals in aqueous solution of glutamic acid and monosodium glutamate crystals in aqueous solution of monosodium glutamate, are investigated over sizes front 1 to 100 mum. It is found that the same properties are significant It for both material systems generally. These are the densities of both phases, shear rigidity of the particles, and sound speed and attenuation of the continuous phase. For these material systems, the size and concentration returned by analysis of ultrasound attenuation are insensitive to several properties which are required for the full Epstein - Carhart - Allegra -Hawley model: thermal dilation, thermal conductivity and heat capacity of both phases. and sound attenuation of the particulate phase. (C) 2003 Elsevier B.V All rights reserved.