The changes occurring in metallic titanium specimens during hydrogenation, that are accompanying by high amplitude acoustic emission signals, have been studied. It was determined that the most probable reason for generation of these signals is crack formation in hydrogenated specimens as a result of internal stresses caused by structural changes in material. Also it was determined that typical sizes of the cracks are comparable with particle sizes of hydrogenated specimens, and the atomic ratio [H]/[Ti] in a solid phase, when crack formation is the most intensive, is generally lower for titanium sponge than for powder made from this sponge, which is explained by a larger specific surface of powder comparatively that of sponge. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.