A numerical study of the effect of viscothermal losses on an acoustic black hole

The omnidirectional acoustic absorber introduced in 2010 by Climente et al. [3] is an acoustic analogue of the quantum black hole for airborne sound in two dimensions. It consists of a shell, which acts like a gradient index lens, and an absorbing core both made of periodic distributions of cylindrical rods. The energy dissipation of this acoustic black hole is numerically studied using the boundary element method, showing that the dissipation is due to viscothermal losses in the core, which are greatly enhanced due to the surrounding shell. We also concluded that discrepancies with measurements should be attributed to spurious losses existing in the experimental setup, which play a non-negligible role in the measured losses.