impedance

6.15  impedance. At a specified frequency, quotient of a dynamic acoustic variable (e.g., force, sound pressure) by a kinematic acoustic variable (e.g., vibration velocity, particle velocity), or quotient of a voltage by a current.

Annotation 1          The term impedance is normally applied to a linear system and to steady sinusoidal signals.

Annotation 2          In the case of a transient, impedance as a function of frequency is the ratio of the respective Fourier or Laplace transforms.