Design of an acoustic metamaterial-based silencer

Dissipative silencers attenuate the sound by converting acoustic energy into heat due to the friction in the voids between the oscillating gas particles and porous or fibrous absorbent ma-terials. However, they present some criticalities, related to the use of these materials: too high thicknessesnecessary to obtain good performance at low frequencies and then increasing costs; problems related to air quality control (bacterial contamination and presence of fibers). In this paper an alternative solution is presented in order to overcome these criticalities. The idea is to realize a silencer basedon parallel-assembled acoustic metamaterials, which are ar-ranged in an optimized configuration. For this purpose a new metamaterial was designed, whose acoustic behaviour is analytically described by using the Transfer Matrix Method (TMM), while numerical modeling is performed witha Finite Element software (FEM). Ex-perimental investigations were carried out on a sample of the previously designed metamate-rial made by 3D printing. The experimental results in terms of the Transmission Loss (TL) show a good agreement with values of the analytical and numerical models.Furthermore, combining FEM and TMM models, a numerical-analytical hybrid model has been developed, which reduces the computational costs and time, simplifying the design of the silencer. Based on the above-mentioned silencer an example application is then finally provided, showingthat it is possible to obtain excellent TL values in small spaces and in desired frequency range

Keywords:

Acoustics , Silencer , Metamaterials , Trasmission Loss