Case A: micro-perforated panel with 5, 10 and 15 mm air gaps
Measured data traced from Fig. 9 of Sekar, V., Eh Noum, S. Y., Putra, A., Sivanesan, S., Chin, K. C., Wong, Y. S., & Kassim, D. H. (2021). Acoustic properties of micro-perforated panels made from oil palm empty fruit bunch fiber reinforced polylactic acid. Sound & Vibration, 55(4), 343–352. https://doi.org/10.32604/sv.2021.014916 (CC BY 4.0).
| Air gap | f peak, simulation | f peak, measurement | Δf | α peak, sim / exp |
|---|---|---|---|---|
| 5 mm | 2610 Hz | 2720 Hz | −4.1 % | 1.00 / 0.99 |
| 10 mm | 1800 Hz | 1900 Hz | −5.2 % | 1.00 / 0.99 |
| 15 mm | 1485 Hz | 1575 Hz | −5.7 % | 0.99 / 0.98 |
The simulation reproduces the peak absorption, the shape of each curve, and the shift of the peak to lower frequency as the air gap grows. The measured peaks sit 90–115 Hz (about 5%) higher in frequency, a consistent offset across all three gaps. The simulation was solved in 45 Hz steps.
Case B: 3D-printed periodic lattice (OPC-5) with a 40 mm air gap
Measured data traced from Fig. 12(b) of Zieliński, T. G., Opiela, K. C., Pawłowski, P., Dauchez, N., Boutin, T., Kennedy, J., … Groby, J. P. (2020). Reproducibility of sound-absorbing periodic porous materials using additive manufacturing technologies: Round robin study. Additive Manufacturing, 36, 101564. https://doi.org/10.1016/j.addma.2020.101564. The sample has a 5 mm periodic cell and is 60 mm thick.
| Peak | f, simulation | f, measurement | Δf | α, sim / exp |
|---|---|---|---|---|
| 2nd | 2040 Hz | 1970 Hz | +3.6 % | 0.87 / 0.84 |
| 3rd | 3720 Hz | 3675 Hz | +1.2 % | 0.94 / 0.91 |
| 4th | 4620 Hz | 4665 Hz | −1.0 % | 0.98 / 0.96 |
The comparison covers 800–6000 Hz; the traced measurement below about 800 Hz was not reliable enough to compare. The simulation was solved in 60 Hz steps.
Interactive charts for both cases are on the homepage.
Limitations
- Not an accredited measurement. The results simulate the ISO 10534-2 and ASTM E2611 test configurations. They do not replace an accredited laboratory report for certification or compliance.
- Normal incidence only. Tube results, physical or numerical, are for normal incidence. They differ from random-incidence absorption measured in a reverberation room (ISO 354) and from building-acoustics sound reduction ratings.
- As designed, not as printed. The model uses your CAD geometry. Printed samples differ through surface roughness, trapped powder or resin, and dimensional tolerance, and these differences usually explain most of the gap between a model and a physical tube test. An as-printed tolerance study is available as a custom project.
- Geometry required. Foams and fibrous materials without a geometry file are outside the scope of this method.
- Flexible parts. If your design includes thin membranes or parts expected to vibrate, mention it in your brief so we can confirm the modelling approach before quoting.