ANOMALOUS BEHAVIOR OF LEAKY SURFACE-WAVES FOR STIFFENING LAYER NEAR CUTOFF

The propagation of surface acoustic waves has been investigated for a layered system (water-isotropic layer-isotropic substrate) where the l ayer is faster than the substrate. It has been found that when the vel ocity of the surface wave reaches the velocity of the shear wave of th e substrate (cutoff) the behaviour of the attenuation has an anomalous character. Attenuation drops down towards zero below cutoff and incre ases abruptly beyond cutoff. Acoustic microscopy measurements on alumi num coated with oxalic oxide film were in coincidence with theory. (C) 1997 American Institute of Physics.