Sound intensity is a vector that quantifies the flow of acoustic energy going through a segment of surface.
Measuring sound intensity is a technique to determine sound power, especially in industrial environment where free field conditions cannot be achieved. Traditionally the measurement of sound intensity is performed by a P-P probe, which consists of a microphone pair, measuring the averaged sound pressure at the center of the space separating the two microphones () and the estimated particle velocity (). Sound Intensity is then computed from these two quantities:
ISO 9614 standard specifies two measurement methods. The point-by-point method, described in the part 1, makes possible to localize the loudest components of a sound source, whereas the scanning method, described in the part 2, is time efficient but enables only to determine the sound power.