Over the last few years a large number of chemists and engineers working in synthesis and materials processing are interested in applications of ultrasound. Ultrasound may lead to higher yields, higher selectivities or even new products. The development of fundamentals for the design of sonochemical reactors is still in the beginning. In this paper linear effects of sound fields in sonochemical reactors in a homogeneous phase are investigated. Scale-up effects in some types of reactors have been calculated, especially the energy density distribution within the reactor. From this distribution the probabilities of the generation of cavitation bubbles can be calculated.