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Acoustic-Structure Interaction: Modeling Sound Transmission Loss (STL) of a Finite Cylindrical Shell"

Posted 2026/07/08 5:53 GMT-4 Structural & Acoustics, Acoustics & Vibrations Version 6.1 0 Replies

Rajat Mishra

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I everyone, I am trying to model the Sound Transmission Loss (STL) through a finite-length, thin-walled circular cylindrical shell in COMSOL Multiphysics and validate it against an analytical paper. Here are the specific details of the problem setup: Geometry & Physics: A finite-length isotropic cylindrical shell modeled using Love's thin shell theory. Acoustic Environment: The shell is excited from the outside by an oblique incident harmonic plane sound wave. The transmitted wave enters an interior anechoic cavity (non-reverberant / inward-traveling waves only). Boundary Conditions: The cylinder is Simply Supported (S-S) at both circular ends (v=0, w=0, N_{xx}=0, M_{xx}=0). I plan to use the Acoustic-Structure Interaction (Frequency Domain) interface with the Shell module for the structure and Pressure Acoustics for the fluid domains. Could anyone guide me on the best practices for setting up: The Background Pressure Field for an oblique incident plane wave acting on the outer cylindrical surface. The Perfectly Matched Layer (PML) or radiation boundary conditions inside the cylinder to properly simulate the anechoic core without artificial reflections. The exact constraints in the Shell interface to correctly replicate the Simply Supported conditions for a vibrating shell. Any model templates, expressions, or advice on capturing the stiffness, resonance, and mass-controlled regions accurately would be highly appreciated!

Update on my current COMSOL setup and the issue I'm facing: To give more context, here is what I have already done in my model: Geometry: I have modeled a thin finite-length steel cylinder. Around this inner cylinder, I created a larger concentric cylinder domain to apply the Perfectly Matched Layer (PML). Material & Domains: Since both ends of the inner finite cylinder are open and the paper assumes air inside and outside, I have assigned Air to the entire domain inside the larger cylinder (which automatically covers both the exterior fluid and the fluid inside the open inner cylinder). Physics & Coupling: For the Acoustic-Structure Interaction, I have selected both the inner and outer curved surfaces of the steel cylinder. Loading & BCs: I implemented the Simply Supported boundary conditions on the shell edges. To simulate the external oblique plane wave, I applied a Boundary Load as a pressure distribution directly on the outer surface of the inner cylinder. The Issue: While the simulation runs and I am getting graphs, the results are not convincing and do not match the analytical curves from the paper. I suspect there might be an issue with: How I am applying the oblique plane wave as a manual Boundary Load instead of using COMSOL's built-in Background Pressure Field or Incident Acoustic Fields.

Could anyone please point out the flaws in this approach or suggest how to correctly set up the incident plane wave and acoustic-structure coupling for this specific open-ended case?

please help me ,this is the paper link I am trying to get results in comsol

Golzari, M., & Jafari, A. A. (2019). "Sound transmission through truncated conical shells." Applied Acoustics, 156, 186-207.

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cylinder_TL_discussion.mph

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