Multicavity structures with triply periodic minimal surface for broadband and perfect sound absorption manufactured by laser powder bed fusion

This research proposes a multicavity and a graded structure design method for triply periodic minimal surface (TPMS) structures with broadband and perfect sound absorption. TPMS structures were manufactured by laser powder bed fusion. The sound absorption coefficient curves and acoustic band structure of TPMS are analyzed using a two-microphone impedance tube. As the thickness of TPMS structures increases, the noise reduction coefficient of TPMS structures increases linearly, and the first resonance frequency shifts to the lower frequency. The acoustic band structures indicate that the acoustic bandgap of TPMS structures shifts to a lower frequency with increasing thickness. Diamond has the highest noise reduction coefficient among these four types of TPMS. The TPMS with a multicavity design has multiple resonance peaks. Notably, the five resonance peaks of the multicavity-I-Wrapped Package (IWP) are all above 0.94, achieving near-perfect sound absorption over a wide frequency range. The semi-absorption bandwidth of the multicavity-TPMS structure has been widened, except for multicavity-diamond structures. Both uniform and multicavity TPMS present a subwavelength absorption peak. The graded design method can broaden the semi-absorption bandwidth of TPMS, and the combination of graded and multicavity designs can further enhance broadband and achieve perfect sound absorption.