This is the author’s version of a work that was accepted for publication in the Journal of Sound and Vibration. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published at: http://dx.doi.org/10.1016/j.jsv.2006.07.035An efficient method of reducing edge reflections of flexural waves in plates or bars based on the 'acoustic black hole effect' has been recently proposed and described theoretically by one of the present authors (V.V.K). The method utilises a gradual change in thickness of a plate or bar, partly covered by thin damping layers, from the value corresponding to the thickness of the basic plate or bar (which is to be damped) to almost zero. The present paper describes the results of the experimental investigation of the damping system consisting of a steel plate of quadratic shape (wedge) covered on one side by a strip of absorbing layer. The results of the measurements of point mobility in such a system show that for a wedge covered by an absorbing layer there is a significant reduction of resonant peaks, in comparison with the uncovered wedge or with the covered plate of constant thickness. Thus, the measurements confirm the existence of the acoustic black hole effect for flexural waves and demonstrate the\ud possibility of its use in practice

Acoustic black holes are relatively new physical objects that have been introduced and investigated mainly during the last decade. They can absorb almost 100% of the incident wave energy, and this makes them very attractive for such traditional engineering applications as vibration damping in different engineering structures and sound absorption in gases and liquids. They also could be useful for some ultrasonic devices using Lamb wave propagation to provide anechoic termination for such waves. So far, acoustic black holes have been investigated mainly for flexural waves in thin plates, for which the required gradual changes in local wave velocity with distance can be easily achieved by changing the plates, local thickness. The present paper provides a brief review of the theory of acoustic black holes, including their comparison with optic black holes introduced about five years ago. Review is also given of the recent experimental work carried out at Loughborough University on damping structural vibrations using the acoustic black hole effect. This is followed by the discussion on potential applications of the acoustic black hole effect for sound absorption in air.

This article was published in the Journal of Sound and Vibration [© Elsevier Ltd.] and the definitive version is available at: http://dx.doi.org/10.1016/j.jsv.2010.05.019The reduction of flexural vibration in plate structures has been investigated using the recently reported acoustic black hole effect for flexural wave reflection in plates with the local thickness varying according to h(x) = epsilon x(m) and m >= 2. Since sharp edges of such plates (wedges) are always truncated before x=0, the real reflection coefficients are relatively high, therefore the application of a small amount of damping is required to achieve large reductions in vibration amplitude. This paper presents a numerical model of a plate incorporating an acoustic black hole wedge, with predictions for vibration amplitudes. These are compared to equivalent experimental measurements for a range of applied damping layers. It is concluded that the above-mentioned power-law wedges can be used as effective vibration dampers in plate structures over a wide frequency range of interest. (C) 2010 Elsevier Ltd. All rights reserved