Comparison of the modal properties of a stiff layer embedded in a solid medium with the minima of the plane‐wave reflection coefficient

Waves which propagate along embedded layers offer potential for the nondestructive characterization of the layers and of the boundary conditions between the layers and the embedding medium. However, it is known that the minima of the reflection coefficient, popularly used to measure the modal properties of leaky waves in plates immersed in fluids, do not correlate precisely with the dispersion curves and may be particularly misleading when the embedding medium is solid and of the same order of impedance as the layer. This paper is the first of a pair which study the practical case of a thin solid layer which is embedded at the bondline of a diffusion bonded titanium joint and is slightly stiffer than the titanium. In this paper the modal properties of the layer are compared with the plane‐wave reflectivity; the second paper [J. Acoust. Soc. Am. 97, 1638–1649 (1995)] addresses the near‐field response of the system to a finite acoustic beam. It is demonstrated in this paper that the loci of the reflection c...