Increased Radiation Efficiency Using Band Gap Effect

Periodic arrangements of elements, such as scatterers, local resonators, and inertial amplifications can induce bandgap phenomena, which result in vibration isolation in mechanical systems due to a significant reduction in the energy transmission from source to receiver. This effect has led to vibro-acoustic applications focusing mainly on the reduction of structure-borne noise. Here, we propose to broaden the application range by utilizing the bandgap effect to increase the efficiency of sound radiation from vibrating mechanical structures. The increase in radiation efficiency is caused by the enhanced vibration localization near the excitation point. In order to illustrate the phenomenon, a one-dimensional mass-spring model with periodically placed local resonators is examined and with this theoretical model vibration localization and sound radiation efficiency are analyzed. An experimental validation is carried out on a plate structure. For the specific case, an increase in radiation efficiency up to 10 dB at frequencies above 2 kHz is demonstrated.