Recently there have been intensive studies [1,2,3] of the coefficient of reflection of ultrasonic waves from fluid-loaded composite plates. Attention has been given mainly to the loci of the reflection coefficient (RC) zeroes as functions of frequency and angle of ultrasonic wave incidence. Interest in the RC zeroes (maxima of the transmission coefficient) arose originally from their association with the leaky Lamb waves in the plate which is valid only for low fluid densities [4]. Independently of the physical meaning of the RC zeroes the spectrum carries important information on the properties of the composite and may be used for reconstruction of the elastic constants from the experimental data [5,6]