Prediction of sound fields in cavities with sound absorbing materials

A sound field in a three-dimensional cavity containing sound absorbing materials was studied using the boundary element method. The sound absorbing material was considered as bulk reacting, and its effective density and propagation speed were measured by a technique based on the transfer function method. Two cavity models were utilized to assess the accuracy of calculation: one was a cavity with a bulk of sound absorbing material within the interior, and the other was a larger cavity divided into two smaller cavities by a panel of the sound absorbing material. Frequency response curves, resonance frequencies, and damping ratios calculated for the cavity models were compared with experimental ones. The excellent agreement achieved suggests that the present method is sufficiently reliable to predict the acoustic properties of the sound field in a cavity containing bulk-reacting sound absorbing materials.