Sound radiation of rectangular plates containing tapered indentations of power-law profile

In this paper, the results of the experimental investigations into the sound radiation of vibrating rectangular plates containing tapered indentations of power-law profile are reported. Such tapered indentations materialise two-dimensional acoustic black holes for flexural waves that result in absorption of a large proportion of the incident flexural wave energy and, therefore, cause efficient damping of plate’s flexural vibrations. A multi-indentation plate was compared to a plain reference plate of the same dimensions, and the radiated sound power was determined in accordance with ISO 3744. It was demonstrated that not only do such multiple indentations provide substantial reduction in damping of flexural vibrations within the plate, but also cause a substantial reduction in the radiated sound power. This paper also considers the effect of distribution of the plate’s vibrational response on the amplitudes of the radiated sound. It is shown that, despite an increase in the amplitudes of displacements at the indentations’ tips, the overall reduction in vibration level over the plate is large enough to result in substantial reduction in the radiated sound power.