Sound Radiation of Plates with Embedded Circular Acoustic Black Hole Indentations

The Acoustic Black Hole (ABH) phenomenon has shown promises for sound and vibration control. In this paper, a 2D Daubechies wavelet model is proposed to investigate the sound radiation properties of a plate embedded with a circular ABH indentation. The model is shown to provide an accurate prediction of both structural vibration and its sound radiation in the mid-to-high frequency range where systematic ABH effects are expected. Analyses show the appearance of a subsonic region inside the ABH cell above the critical frequency of the plate, due to the ABH-specific phase velocity reduction of the bending waves. Surrounding the center of the ABH indentation and drawing energy away from the supersonic region of the plate, this subsonic region exhibits low sound radiation efficiency, thus resulting in an overall reduction in the sound radiation of the plate as compared to its flat counterpart. Sound radiation properties and the transonic boundary changes within the ABH indentation are scrutinized and quantified. Analyses on the sound radiation efficiency of the ABH plate with a damping layer show the importance of optimizing its thickness in order to maintain an effective vibration energy dissipation and a reduced sound radiation efficiency at the same time.