Sound Insulation Properties of Thin Plate with Embedded Two-dimensional Acoustic Black Hole

One of the important potential applications of acoustic black hole (ABH) effect is to improve the vibration damping and sound insulation performances of thin-walled structures by embedding multiple ABHs. However, conventional two-dimensional ABHs with power-law profile contain zero thickness at their centers, which consequently lead holes in the structure. For structural integrity, modified ABHs are usually preferred in real structures. In this study, the sound insulation properties of ABH plates with two different types of modified ABHs were investigated. The first type of modified ABHs, defined as type-A, has a uniform remaining thickness added to the conventional power-law profile and the second type of modified ABH, defined as type-B, has a uniform platform at the center of indentation, the thickness of which is also changed as a parameter. Each plate in this work has four ABHs. The transmission loss, transmitted sound power, modal loss factor and radiation efficiency of these ABH plates were computed using finite element method and compared with those of uniform plate. The ABH plates exhibit higher transmission loss of sound than the uniform plate in the effective frequency range from 2 kHz to 7 kHz. The physical mechanism of higher transmission loss in ABH plates was discussed with the help of vibration modes at different frequencies. The type-B ABH plate outperforms type-A ABH plate in sound insulation performance when they have the same remaining thickness. Even when the thickness of platform in type-B ABH is doubled, the type-B ABH plate still has almost the same transmission loss as the type-A ABH plate. Finally, the noise insulation characteristics in plate with embedded ABHs were verified by experiments.