Hi Abdolrasol,

For the media that aren't water, I assume that they're solids of some kind? If so, what kind of waves have been excited in these media, P-waves or S-waves or a mixture of both? The wave velocities in these solids will be different for each type of wave and there will be different wave impedances for each type too which could lead to the results you're seeing. What kind of excitation are you using? Point source? Plane-wave?

Ray,

Thank you for the response. To answer your questions:

Material 1 and 2 are both solids. Pressure waves only, emitted from a piezoelectric transducer. Plane waves and no point source.

I guess, your problem more closely matching with the contact interaction problem between these two materials (water and solid). It looks like boundary of solid material 1 is too rigid compared to material2, therefore the wave is not smoothly propagating into solid.

A graphical image of model can be helpful for better understanding of the problem.

Hi Abdolrasol,

Are your plane waves at normal incidence to the interface? If not, you cannot accurately determine the transmission and reflection coefficients using just the impedances. There will be mode conversion, and some of your incident compression wave energy will be converted into shear waves, which will not be reflected back into the liquid. At critical angles of incidence, you will also generate Rayleigh (surface) or Lamb waves in the solid, depending on its thickness. These angles can be determined using Snell's Law. As your two materials have different sound speeds, at an identical (non-normal) angle of incidence, they could have very different reflected energies.

Hi Abdolrasol,

What about the transmission amplitude, for the two cases?

How did you connect the Solid boundary to the water boundary?

At the boundary, if you have an option to choose the slave/master material, do not give water as the master material.