Experimental observation of anomalous absorption of bulk shear acoustic waves by a thin layer of viscous fluid

This letter presents the results of an experimental observation and investi gation of the recently predicted anomalous absorption of bulk shear acousti c waves polarized normally to the plane of incidence by an ultrathin layer of viscous fluid between two elastic media. Strong increase of the absorpti vity of the incident wave by the fluid layer has been observed at layer thi cknesses that are much smaller than the wavelength and wave penetration dep th into the fluid. A good agreement between the experimental results and th e theoretical predictions has been achieved. (C) 2000 American Institute of Physics. [S0003-6951(00)02415-3].