## 5aAA9. A rigorous linear model for the local reverberation time.

### Session: Friday Morning, December 6

### Time: 10:15

**Author: Domenico Stanzial**

**Location: Dept. of Acoust., C. N. R. Cemoter, v. Canal Bianco 28, 44044 Cassana, Ferrara, Italy**

**Abstract:**

Recent advances in energetic analysis of sound fields show that three local
sound field indicators (eta), (xi), (sigma) accounting, respectively, for the
sound radiation, the sound absorption, and the sound energy velocity at any
given location of a general sound field can be usefully employed for modeling
the reverberation process as a linear feedback system. The input and the output
of this black-box model of a general reverberant field are the sound energy
density of the associated free-field and the actual sound energy density of the
reverberant sound field. It turns out that the energy transfer function of the
model system is simply given by the time-average speed of the sound energy at
the given location. The local reverberation time formula is obtained from this
model by adding up how many ``characteristic times of the acoustic system'' are
necessary in order to get an energy feedback contribution 60 dB lower than the
steady-state sound energy level of the associated free-field.

ASA 132nd meeting - Hawaii, December 1996