Experimental checking of a basic relationship involving active and reactive intensity

The present work is concemed with the experimental checking of the general relationship A^2 + Q^2 =<p^2>*<v^2> involving the active intensity A, the reactive intensity Q, the sound pressure p and the particle velocity v, as pointed out in a recent paper by Schiffrer and Stanzial. Measures of A, Q, p, v, have been carried out by means of a commercially available B&K2133 intensity meter for various monochromatic and wide band random and non-random fields generated inside a square duct. Collected data for A^2 and Q^2 are plotted against the corresponding values of <p^2> and <v^2>, thus obtaining a checking for the relationship within the experimental error of ± 1dB.