Omnidirectional sound wave absorption based on the multi-oriented acoustic meta-materials

Acoustic meta-materials have become a hot topic in rotary equipment sound absorption with advantages of small size and additional mass, but the effectiveness is significantly limited by the incident angle and the absorption performance is not good in random sound fields. This paper proposes a multi-oriented acoustic meta-material (MOAMM) that can be applied in omnidirectional sound wave absorption, which is composed of unit cells with different orientations. The single cell is designed as a double-cavity labyrinth structure, and the unit cells are distributed uniformly in a circumference to adapt to incident waves from different directions. The absorption performance is compared with the structure of same-oriented distribution, and parametric studies are carried out for the change of sound absorption performance of MOAMM. Results show that the sound absorption coefficient of MOAMM maintains over 0.8 when facing with sound waves from different direction, and the frequency range changes with the entrance width, channel width and cell size. Experimental results have verified the excellent performance of the proposed structure, which provides new approaches for effective control of sound radiation.