Wide-angle asymmetric acoustic absorber based on one-dimensional lossy Bragg stacks

Based on one-dimensional lossy Bragg stacks, an asymmetric absorber is realized for low-frequency sound waves, that is, perfect absorption can be obtained when sound waves are normally incident from one side while a small absorption can be obtained from the opposite side. Moreover, the asymmetric absorption persists for a wide incident angle of sound waves in the range from 0° to 42° with the absorptive coefficient larger than 90% from one side while less than 20% from the other side. By changing the thickness of the top sublayer, a series of interesting absorption phenomena such as Fano-resonance type absorption are further investigated.