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. Sec. Am. 99, 1868-1876 (1996)]. The quantity a, which has the same time dependence as the squared acoustic pressure arid 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.