Theoretical and experimental results concerning diffraction of ultrasonic waves on periodic liquid–elastic solid interfaces are presented. A general system of linear equations is established and solved numerically for triangular surfaces. Theoretical results are in good agreement with measurements obtained by a broadband pulse-echo system in the region where the wavelength is of the same order of magnitude as the period and much greater than the depth of the grating. In the spectrum of the reflection coefficient frequency minima are identified as the surface waves excited along the periodic surface.

Reflection of bounded sound beams incident from a liquid on solid half-spaces or plates and transmission through plates are described using one new mathematical model. Since the exact expressions for reflection and transmission coefficients are used, reflected and transmitted beam profiles can be predicted at any angle of incidence. Using a simple representation by inhomogeneous infinite waves, it is possible to obtain analytical expressions for reflected and transmitted beams, whatever the form of the incident profile may be. As the bounded beam is built up by inhomogeneous waves, all propagating in the same direction, it can be easily interpreted and it is possible to detect those parts that are generating surface waves.

In studying the reflection and transmission of inhomogeneous plane waves at liquid–solid interfaces, it is found that the theory predicts a minimum in the reflection coefficient at the Rayleigh angle. This phenomenon has not been predicted by previous treatments of homogeneous plane waves. A second surprising point is that the theory predicts that the modulus of the reflection coefficient becomes greater than unity for angles larger than the Rayleigh angle. A physical interpretation of this result is given, and it is shown that it is consistent with the conservation of energy.

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