ICSV26

3D printed Helmholtz resonators were tested on an impedance tube for absorption coefficient in 400-6400 Hz frequency range. Unexpected absorption phenomenon was reported. Two hypotheses to explain the mechanism of energy dissipation were verified: viscous friction in 3D printed-induced porosity and vibration of thin viscoelastic structure in a membrane-like absorber behavior. Using a combined experimental and analytical approach, it was shown that vibration of thin-wall, rather than the induced porosity, was at the origin of energy dissipation. The results presented in this work alert acoustician community about a dissipation effect related to the vibration of thin structures and provide new possibilities for development of 3D printed sound absorbing materials.