In acoustics is there something analogous to skin depth in EM?

Hi all

The reflection and transmission of a pressure wave at a boundary depends on the relative impedance of the two media.

I'm pretty new to acoustics but the textbook I've been looking at doesn't seem to specify that the such calculations are only valid when the medium is at least a few wavelengths thick.

Surely the reflection at a boundary with a material less than a wavelength thick will be very different from that of a material many wavelengths thick? Is there a specific technical term for such things in acoustics? Is there an analogous concept to skin depth in acoustics?

Thanks