Exploration of Sound Absorption Properties of 3D-Printed Hybrid Materials through Impedance Tube Measurements

Additive manufacturing technologies can be used to produce innovative and efficient acoustic materials that can be designed with tailored complex inner structures and topological surfaces to address specific frequency-related acoustic problems. These fabrication techniques can facilitate the production of hybrid materials, which combine sound absorption ad diffusion properties. This is usually achieved by combining porous layers with irregular hard elements.This contribution focuses on the sound absorbing performances of 3D printed hybrid acoustic materials (HAM) and explores the challenges associated with their characterization in an impedance tube. The effects of the combined hard and porous layers have been investigated on two comprehensive examples that can serve as benchmark. Both layers have been obtained by printing the same material, i.e., thermoplastic filament (1.75 mm) PLA. It found that the sound absorption properties of the tested HAM samples are significantly influenced by many factors, namely by the open-porous material structure, the sample thickness, and the presence or absence of a hard layer on top of the porous one. This information can provide useful insight to further optimize the design of HAMs to improve their sound absorbing performances.