Broadband sound absorption by acoustic metasurface of planar array of small Helmholtz resonators

An acoustic metasurface (AMS) gives a broadband sound absorption by a planar periodic array combining small resonant modules tuned at various frequencies. This study introduces a formulation of sound absorption coefficient of the AMS and discusses the calculated examples by comparing with the measured sound absorption characteristics of the AMS consisted with the planar array of small Helmholtz resonators which have a multiple folded long neck and an airtight cavity.