ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

2pAAb3. New developments of the ``sound particle'' concept in room acoustics.

Domenico Stanzial

Natl. Res. Council of Italy, Cemoter Acoust. Dept., via Canal Bianco, 28, I-44044 Cassana, Ferrara, Italy

Nicola Prodi

CIARM c/o Cemoter, Ferrara, Italy

The concept of a sound particle, that is a small amount of acoustic energy which is supposed to move inside the sound field, has been used from long time in room acoustics, principally in connection with the statistical interpretation of the reverberation theory and more recently with the ray-tracing-based computer simulations. New research on energetic properties of acoustic fields [G. Schiffrer and D. Stanzial, ``Energetic Properties of Acoustic Fields,'' J. Acoust. Soc. Am. 96, 3645--3653 (1994)] leads to the possibility of rigorously defining, by means of the energy transfer velocity, the trajectories of sound particles. Furthermore, the general decomposition of the air-particle velocity v into one part v[inf p], which has the same time dependence as the acoustic pressure p, and the other one v[inf q]=v-v[inf p] such that =0, allows one to define two separate kinds of sound particle trajectories. These different behaviors are connected, respectively, to the instantaneous active and reactive acoustic intensities. A brief summary of the theoretical framework and some visualizations of sound particle trajectories for simple model fields will be presented.