Together, they determine the sound intensity of the wave.

Sound intensity, denoted I and measured in W·m^-2 in SI units, is defined by

where
* p is the sound pressure,
* v is the particle velocity.

Acoustic impedance

Acoustic impedance, denoted Z and measured in Pa·m^-3·s in SI units, is defined by

where
* is the Laplace transform of sound pressure,