Sonic black hole duct

The sonic black hole is a type of acoustic black hole that attenuates sound propagation via the acoustic black hole effect. This phenomenon is when an incident acoustic wave propagates through a power-law tapering geometry causing the wavelength to compress, the wave speed to decrease, and the time for the wave packet to reach the exit to extend infinitely. As a result, the wave never reaches the exit, so it cannot be reflected or transmitted. However, this outcome relies on the taper approaching exactly zero, which is impossible to manufacture. Therefore, the taper must be truncated leading to imperfect sound absorption. One method to increase the sound absorption is by applying perforations to the rings. This study explores the effect that varying the perforations on the sonic black hole’s rings has on the absorption coefficient from 1 to 5 kHz.