### ASA 127th Meeting M.I.T. 1994 June 6-10

## 4pPA9. Influence of finite impedance walls on the sound field in an
enclosure.

**Kavitha Chandra
**

**
Charles Thompson
**

**
**
*Ctr. for Advanced Comput., Univ. of Massachusetts Lowell, Lowell, MA
01854
*

*
*
**Martin G. Manley
**

**
**
*Boston Univ., Boston, MA 02215
*

*
*
A numerical technique is presented for computing the pressure distribution
in the interior of a rectangular enclosure. The analysis models the effect of a
nonuniform distribution of wall impedance. The normal modes for this problem
are evaluated by solving Green's integral equation. The wall admittance
function is represented as the sum of a mean value superimposed by spatially
varying fluctuations. An asymptotic series solution for the pressure about the
mean value of the wall admittance is not guaranteed convergence for functions
that exhibit large perturbations from the mean. The convergence of the series
is shown to be improved by transforming the pressure to a rational functional
representation. The superposition of normal modes determined by this technique
serves as Green's function that allows the acoustics of the enclosure to be
modeled for a variety of sources. The effect of the wall impedance on the
transient response and the reverberation time of the room is presented. [Work
supported in part by DOE.]