Sound absorption characteristics of the two-dimensional dual-graded anechoic coating

Abstract The anechoic coating can be applied to absorb underwater sound waves. To improve the performance of the current anechoic coating, a two-dimensional dual-graded anechoic coating (2D DGAC) which consists of background material, graded solid cores, and graded cavities has been proposed. The sound absorption characteristics of 2D DGAC have been investigated numerically, compared with the 2D mono-graded anechoic coating (MGAC) and uniform anechoic coating (UAC). The dual contribution including multi-cavity resonances and multi-local resonances excited by graded air cavities and steel cores in DGAC could result in effective sound energy dissipation. The improvement of sound absorption performance of DGAC could be attributed to resonances excited by graded cavities compared with that of UAC in 5500–10 000 Hz and local resonances of graded steel cores compared with that of MGAC in 1600–5700 Hz.