I am working with a 3D cuboid-shaped structure for acoustic modeling in ABAQUS, having 3 different section steel, cement and granite (partitioned in the figure). In the steel, cement and granite interfaces, I just assigned section based on their properties. However, I am confused about if I need to add tie constraints in those interfaces. Or is there anything more I need to do to assign interface boundary condition. For your information, the sections are perfectly bonded (no slip/ no separation), I need full acoustic wave transmission through the model, and reflection of waves is expected. I tried a simulation without applying any constraints, but not able to see the wave propagation throughout the model in animation, and while plotting the velocity vs time data for a certain node, no reflection is visible in the graph. Could you please suggest me the right way to do it? Please let me know if you need any additional information to help me. Thanks.

Acoustic Modeling tie constraint