Reflection of finite acoustic beams from loaded and stiffened half-spaces

Results of theoretical calculations and experimental measurements on the reflection of finite acoustic beams from a fluid–solid interace in the presence of a loading or stiffening layer on the solid are presented. Measurements with Gaussian-profile acoustic beams are reported on wave-speed dispersion and reflected-beam amplitude distribution for stiffening layers of chromium on either brass or stainless steel. Good agreement is generally observed. Detailed results of calculations of the reflection coefficient to delineate the behavior of cutoff modes for both stiffened and loaded half-spaces are given. A straightforward method for deducing the complex Rayleigh wavenumber directly from the reflection coefficient is discussed. Comparisons between direct numerical integration of the reflected beam distribution and results of an extended analytical model demonstrate decreasing accuracy of the latter as one nears a mode cutoff.