Acoustic forces on a flexible panel which is part of a duct carrying airflow

Abstract

The acoustic generalized forces on a panel vibrating in the wall of an infinite duct carrying airflow, and due to the presence of the duct, have been derived. The method used has been to consider the acoustic pressures set up in the duct by movement of the panel in prescribed modes. The pressures generated react on the panel itself as well as on the surrounding walls, and generalized stiffness and damping forces have thus been derived. The effect of these forces is generally small but when the panel is large and flexible and the duct cross-sectional area is small then large values of acoustic stiffness and damping are generated for the fundamental mode compared with the mechanical values. In these situations care must be taken in interpreting any results dependent upon panel response.