Acoustic impedance and
specific acoustic impedance are measures of the opposition that a system presents to the acoustic flow resulting of an acoustic pressure applied to the system. The
SI unit of acoustic impedance is the
pascal second per cubic metre or the
rayl per square metre , while that of specific acoustic impedance is the pascal second per metre or the rayl. In this article the symbol rayl denotes the MKS rayl. There is a close analogy with
electrical impedance, which measures the opposition that a system presents to the electrical flow resulting of an electrical voltage applied to the system.