Abstract
One peculiarity of acoustic emission (AE) is the scale invariance of some characteristic statistical quantities, which suggests that similar critical dynamics could rule the elastic relaxation process in different circumstances. In the present paper, after reporting some findings from recent experiments. we show that the statistical behaviour of the AE signals can be reproduced by a generalization of the Born model for elasticity. Depending on the different kinds of disorder and boundary conditions imposed on the system, the onset of long-range correlations in the formation of microcracks (here assumed to be the origin of the AE) can be stimulated or inhibited.