Measurements of newly defined intensimetric quantities and their physical interpretation

This paper deals with the measurement and physical interpretation of the quantities a and r introduced in a previous paper [D. Stanzial, N. Prodi, and G. Schiffrer, “Reactive intensity for general fields and energy polarization,” J. Acoust. Soc. Am. 99, 1868–1876 (1996)]. The quantity a, which has the same time dependence as the squared acoustic pressure and the same direction as the time averaged sound intensity 〈j〉, will be called here “radiating” intensity, while r which has zero average, will be called “oscillating” intensity. A coherent picture of the energy transfer process in steady sound fields based on the decomposition j=a+r of the instantaneous sound intensity will be sketched and discussed. Furthermore, a direct experimental comparison between a and r and the real and imaginary parts of the complex intensity is presented for some field conditions.