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

In this paper, the results of the experimental investigations into the sound of 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 wave energy. A multi-indentation plate was compared to a plain reference plate of the same dimensions, and the radiated sound power was determined (ISO 3744). It was demonstrated that not only do such multiple indentations provide substantial reduction in the damping of flexural vibrations within the plates, but also cause a substantial reduction in the radiated sound power. As the amplitudes of the flexural vibrations of a plate are directly linked to the amplitude of radiated sound from the same plate, this paper also considers the effect of distribution of the amplitude of the plate’s response on the amplitudes of the radiated sound. This investigation concludes that, despite an increase in the amplitude of the displacement at the indentation tip, the overall reduction in the constant thickness of the plate is large enough to result in substantial reductions in the overall vibration response and in the resulting sound radiation of plates containing indentations of power-law profile.