Acoustic interface sections are used to define the section properties of two-dimensional, three-dimensional, and axisymmetric regions that model an acoustic medium undergoing small pressure changes. You use acoustic interface sections when you want to couple the acoustic medium to a structural model. For more information, see “Acoustic interface elements,” Section 26.14.1 of the ABAQUS Analysis User's Manual.
To specify acoustic interface section properties:
From the main menu bar, select Section
Create.
A Create Section dialog box appears.
Tip:
You can also click Create in the Section Manager or select the create section tool 
in the Property module toolbox.
Enter a section name of your choice. For more information on naming objects, see “Using basic dialog box components,” Section 3.2.1.
Select Other as the section Category and Acoustic interface as the section Type, and click Continue.
The section editor appears.
Select an acoustic medium material for the acoustic interface section. If desired, click Create to create a material; see “Creating or editing a material,” Section 12.6.1, for more information.
Enter a value for the section Plane stress/strain thickness. If the section will be used with a two-dimensional region, you must specify the section thickness. ABAQUS/CAE ignores the thickness information if it is not needed for the region type.
Click OK to save your changes and to close the section editor.