Low frequency, broadband and thin acoustic metamaterials for acoustic insulation

This PhD is part of the Horizon Europe MSCA doctoral network METAVISION (METAmaterials for VIbration and Sound reductION – Grant number 101072415). METAVISION is an international consortium of high-profile universities, research institutions and companies located in 7 European countries. METAVISION will train 11 doctoral candidates through intersectoral, multidisciplinary and international joint research and aims to reconcile two conflicting trends. On the one hand, people become increasingly aware of the negative health impact of excessive noise and vibration exposure. On the other hand, every kilogram of mass removed from the logistics chain has a direct economic and ecological benefit. Current noise and vibration solutions at low frequencies require too much mass or volume to be practically feasible. There is a strong need for low mass, compact solutions with excellent noise and vibration characteristics, for which recently emerged so- called metamaterials have shown immense potential. METAVISION aims to develop novel design and analysis methods, revolutionize the manufacturing of metamaterials towards
large-scale and versatile solutions, and advance academically proven metamaterial concepts towards industrially relevant applications.

Elastic and locally resonant metamaterials can achieve high sound attenuation, especially at low frequencies, due to properties resulting from periodic lattice organization or local resonances. In particular, recent studies show that high sound insulation can be obtained when inclusions are inserted into a porous medium in which the skeleton vibrates. Metablocker is a metamaterial developed by Metacoustic, based on these principles; its performance at low frequencies has been demonstrated experimentally. The adaptation of this material to address sound insulation applications is an important issue, which is also attracting a lot of interest from industry. Furthermore, the coupled phenomena between the material and the vibrations of the supporting panel can be organized and optimized in order to improve the trade-off between low-frequency acoustic performance and treatment thickness. The applications targeted by this work are specifically related to acoustic insulation in contexts where the acoustic treatments to be applied must be thin in order to limit the size (transport industry, household appliances, etc.). The particular case of ultra-low frequency attenuation for very specific and demanding industrial and scientific applications
will be investigated.