The operating performance of plant for removal of particles from gases can be influenced by crude gas conditioning and other additive measures. In such processes either additional material or additional energy is introduced into the plant. Set goals are the reduction of particle emission, reduction of operating costs, adaptation to changing boundary conditions, or the opening up of new areas of application for the separators concerned. In the second of these three surveys conditioning by acoustic means is considered. Fundamental aspects of acoustically induced agglomeration are first considered. Possibilities and effects of acoustically influencing electrical separators and filtering separators are then presented, discussed, and - wherever possible - assessed with regard to practical relevance.