Does Melamine Foam Make Soundproof Panels More Effective?

Table of Links

Abstract and 1 Introduction

2 Unit cell design and analysis

3 Unit cell experimental and numerical characterization

4 Rainbow AM labyrinthine panel

4.1 Panel design and fabrication

4.2 FE model of the AM panel

4.3 AM panel characterization

4.4 AM panel sound absorption results

5 Numerical evaluation of different labyrinthine sound absorption panel solutions

5.1 Macrocell with backing cavity

5.2 Results

Conclusions, Acknowledgements, and References

Appendix I

5.1 Macrocell with backing cavity

Given the promising results for the design procedure outlined in the previous Sections, and the good agreement between numerical and experimental results, a further numerical study is performed to evaluate possible developments of the AM-based sound absorption panel. The objective is to assess its acoustic performance under different design configurations. More specifically, three additional configurations are assessed: a) the addition of a melamine foam inside the UCs of the panel; b) the addition of a rigid rear backing cavity applied in correspondence with the uneven bottom surface of the panel (in this case with open apertures), with/without melamine foam filling; c) a combination of a) + b). The acoustic performance of each of these features can be studied and compared to the original configuration (taken as a baseline), again performing FE simulations with COMSOL Multiphysics, focusing on a single marcocell, taken as representative of the panel behaviour. Again, thermoviscous effects need to be accounted for.

In the second configuration, the AM panel is coupled to an additional acoustic domain of a depth equal to four times its side length (Fig.11a and b). Non-reflective Perfectly Matched Layer (PML) boundary conditions are applied to the back of the acoustic domain. Once again, structural domains are considered perfectly rigid, since results from fully vibro-acoustic and simple acoustic simulations give rise to negligible differences. The foam material is chosen as melanine, whose properties are summarized in Table 1.

5.2 Results

Figure 12 shows the calculated absorption coefficient in the three considered cases. The baseline simulation, corresponding to the dashed curve in Fig. 10b, is shown in red. The effect of the presence of a backing cavity (5mm thick) filled with melamine foam (green dashedcurve in Fig.11) is to shift absorption peaks to lower frequencies (the lowest from 1 kHz to about 700 Hz), with a beneficial effect for the attenuation of low frequencies. The addition of a foam filling in the AM cavities, on the other hand, leads to a more uniform absorption coefficient over the whole frequency range, at the expense of a lower efficiency at the AM working frequencies. This solution can however be useful in the case where a more distributed attenuation effect is required over the whole frequency range, rather than at specific target frequencies. Other types of foams can also be considered to optimize the combined effect with the AM.