Average rate of sound energy transmitted in a specified direction at a point through a unit area normal to this direction at the point considered. Unit, watt per square meter (W/m2); symbol, I (ANSI S1.1-1994: sound intensity; sound-energy flux density; sound-power density).
A measure of the sound energy propagated in a specific direction. Measured as watts/square meter over an area normal to the direction of propagation. The term is often incorrectly used when sound level, or sound pressure level is really intended.