Impact of Manufacturing Inaccuracies on the Acoustic Performance of Sound Insulation Packages with Plate-Like Acoustic Metamaterials

Thin plate-like metamaterials (e.g. membrane-type acoustic metamaterials or inhomogeneous plates) have a high potential for improving the sound transmission loss of sound insulation packages, especially in the challenging low-frequency regime. These types of metamaterials have been previously shown to achieve very high sound transmission loss values which can exceed the corresponding mass-law values considerably. However, like many other metamaterial realizations, their extraordinary acoustical performance relies on the periodicity of the sub-wavelength sized unit cells. In particular, for plate-like acoustic metamaterials (PAM) most theoretical and numerical investigations assume a perfect placement of equal added masses - an idealization which cannot be achieved in industrial manufacturing of these metamaterials. This contribution investigates the impact of randomized inaccuracies that can occur in manufacturing on the sound reduction behavior of PAM. First, a numerical model of a finite sized PAM is validated using sound transmission loss measurement data. Then, the simulation model is modified to incorporate randomly varying geometrical parameters of the added masses (such as mass placement, size, etc.). The parameters are randomized according to a Gaussian distribution and the impact of different standard deviations on the sound transmission loss is analyzed. The results indicate that while a random variation of the mass parameters does have an effect on the acoustic performance of the investigated PAM, it becomes significant only for relatively large standard deviations.