“…Many efforts have been reported in this area since the 1990s (Gulyaev and Plessky, 1997;Gulyaev, 1998;Kalantar-Zadeh et al, 2003a, b;Kosevich et al, 1995;Newton et al, 2001;Powell et al, 2004;Kovacs and Venema, 1992;McHale et al, 2001;Plessky, 1995). The challenge is to include the softness (or viscoelasticity) of the testing material into consideration, specifically, when the resonator operates in a liquid.…”