On the connection between wave impedance, sound intensity and kinetic energy in monochromatic fields

Following a recent article by one of the author where the concept of complex intensity has been fully developed from the physical point of view and its spectral properties have been highlighted, the present paper focuses on the relationship between sound energy indicators and wave impedance. It will be shown how the specific impedance of monochromatic, plane quasi-stationary and spherical-divergent waves, is related to the complex sound intensity as defined in ["On the physical meaning of the power factor in acoustics", J. Acoust. Soc. Am. 131(1), 269-280 (2012)], suitably normalized to the kinetic energy density. The relationship will be graphically demonstrated to be true along the direction of the active intensity also for 2-D fields with non-vanishing curl.