A novel semi-active actuator with tunable mass moment of inertia for noise control applications

Semi-active control approaches have been developed and employed for a variety of vibration-reduction applications, including adaptive vehicle suspensions, earthquake protection for civil structures, and more. These semi-active systems require significantly less energy than the corresponding active solutions, while continuing to provide a high level of performance, therefore they are an attractive approach. In the context of noise reduction barriers, semi-active control often refers to piezoelectric patches or stacks connected to shunt electric circuits in order to transform and dissipate mechanical energy. However, a different type of semi-active actuators can also be used to adapt the mechanical features of noise barriers in order to deal with varying noise properties. This paper proposes a novel semi-active actuator with tunable mass moment of inertia. When attached to a noise barrier, it can alter the resonant frequencies and mode shapes of the barrier in order to reduce acoustic radiation at dominant frequencies in the noise. As the presented results show, this actuator can enhance the transmission loss of a noise barrier for time-varying narrow-band noise by more than 10 dB in targeted frequency bands. Alternatively, the proposed actuator can be used to optimize acoustic radiation from a panel acting as a sound source. Both scenarios are considered and analyzed in this paper by employing mathematical modeling, experimental validation and numerical investigation.