Metamaterials have proven effective in addressing multiple technological issues, such as selective sound absorption in the automotive/aeronautical field, enhancing speech recognition in acoustic devices and damping vibrations in civil engineering, Despite their potential, a formalized set of recognized design principles with predictable output properties, quality, scalability, etc. has been lacking, limiting their widespread adoption in applications.
MetaMAPP II – Reloaded aims to develop a metamaterial-based solution to reduce the noise level inside a car cabin, particularly targeting a specific range of medium-high frequencies.
The development of the prototype has involved extensive research and literature analysis on the different families of currently studied and employed meta-materials, with the aim of laying the foundations for the proper product design process.
A substantial part of the workflow has been devoted to the identification of plausible unit cell geometries to meet the fixed requirements. Acoustics finite element simulations have been adopted to assess the properties of unit cells and unit cell clusters. These numerical models are essential to determine the influence of variable design parameters. A subsequent printing and testing phase has been adopted to validate numerical results and choose the best candidate unit cells for the final products.
A step-by-step process involving research and subsequent confrontation with stakeholders has led to a greater focus on transmission properties of the metamaterial panel (referred to as Sound Transmission Loss, or STL), compared to absorption ones. Additional working mechanisms of the labyrinthine cells have consequently been explored, combining purely acoustic absorption effects of the cavities with the elastic behaviour of the cell walls and structure itself.
The final outcome of MetaMAPP II – Reloaded consists of two types of prototypes, a cube and a panel made of metamaterial cells, that demonstrate and certify the acoustic performance of the designed acoustic metamaterial solution.