ACOUSTIC EMISSION INSTRUMENTS AND TRANSDUCERS, NAMELY, INSTRUMENTS AND TRANSDUCERS FOR MEASURING CRACK GROWTH; INSTRUMENTS AND TRANSDUCERS FOR LOCATING CRACK LOCATION; INSTRUMENTS AND TRANSDUCERS FOR SEPARATING SIGNALS CAUSED BY CRACK GROWTH FROM EXTRANEOUS NOISE; INSTRUMENTS AND TRANSDUCERS DESIGNED TO RECOGNIZE A ZERO ORDER SYMMETRICAL LAMB WAVE, A HIGH FREQUENCY SHEAR WAVE, AND A ZERO ORDER ANTISYMMETRICAL LAM WAVE; AND INSTRUMENTS AND TRANSDUCERS FOR MODAL ANALYSIS OF THE ACOUSTIC EMISSIO...