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