Sound transmission through a panel with a hybrid active and semi-active control system

Semi-active control systems require significantly less energy than active solutions, while still providing substantial performance. However, active and semi-active systems can be applied in conjunction as hybrid systems, exploiting both solutions and providing high performance and reduced energy consumption. This paper proposes the use of such a hybrid active/semi-active control system for noise reduction barriers. Accounting for time-varying narrow-band noise, active structural acoustic control (ASAC) guarantees enhanced transmission loss for a noise barrier. Simultaneously, a semi-active element with a tunable mass moment of inertia allows the system to adapt to noise with varying characteristics by altering the mechanical properties of the barrier. Obtained control results demonstrate that the addition of a semi-active element is more effective than an additional active control actuator for reducing sound power in targeted frequency bands. Moreover, the proposed hybrid system may operate in two modes, allowing to further reduce overall energy consumption.