Numerical analysis of active structural acoustic control in an enclosed cavity

A numerical model is applied to study the application and performance of active structural acoustic control (ASAC) in automotive cabins. The vibro-acoustic problem is composed of a rectangular acoustic cavity, representing vehicle compartment, coupled with a free-free panel, representing the windshield, and a simply supported panel, representing the floor panel. In the formulation of ASAC, noise transfer functions are used to calculate the control forces based on their ability to minimize the total acoustic potential energy in a specific region of interest inside the cabin. Results show that when ASAC is applied at the same panel radiating the primary noise, a significant reduction in the total acoustic potential energy in the region of interest is achieved. It was also observed that the performance of ASAC improves more as the number of control forces is increased. However, when ASAC is applied at a panel different than the primary noise radiating panel, ASAC becomes ineffective. Moreover, results indicate that, in this case, increasing the number of control force, does not improve the total acoustic potential energy reduction in the region of interest. It is found that the main reason behind the ineffectiveness of ASAC is the difference in the vibro-acoustic characteristics of the source and control panels as well as the modal coupling between the control panel and cavity modes. This leads to significant modal participations of higher cavity modes in the low frequency response and thus makes ASAC inefficient.