In this paper, the influence of specific mechanical energy (SME) input on the ultrasonic characteristics of extruded doughs with 50% and 70% moisture contents, representing extremes of processes employed in a typical dough processing industry was examined. It is aimed at extending the work on ultrasonic characterization of doughs mixed by conventional techniques, and employing ultrasound to measure the ultrasonic characteristics of extruded dough products. The ultrasound analysis showed that low SME values do not significantly change the ultrasonic velocities of the extruded dough with 70% moisture content. However, for dough of 50% moisture content, velocity values increased as a function of SME input. The dependence of attenuation coefficient on SME and dough moisture content was also sensitive to changes in SME, and can be characterized as essentially an inverse relationship to that of velocity. (C) 2007 Elsevier Ltd. All rights reserved.