Mechatronics, Signal Processing and Control and Acoustics

The propagation of noise and vibration from working machinery is a major problem in a variety of industrial sectors. Traditionally, passive isolation solutions have been used to tackle the problem but the performance of these is often limited particularly at lower frequencies and a number of active control solutions have been proposed. An alternative passive approach that has significant potential for low frequency, subwavelength control is to exploit designs from the emerging field of metamaterials. Metamaterials possess physical properties not seen in naturally occurring media and of particular interest here are materials with a periodic locally resonant structure. At resonance the density and bulk modulus of such materials can become simultaneously negative leading to a refracted wave that lies to the opposite side of the incident normal than one would expect in a regular transmission medium. These novel properties have been proposed as a potential solution to achieve acoustic cloaking and subwavelength acoustic lenses. However, of more importance in vibration and noise isolation applications is the appearance of band gaps at low frequency where wave transmission is blocked and high levels of attenuation occur.

A disadvantage of the passive metamaterial designs, however, is that the band gaps occur over fixed and very narrow frequency spans. A potential solution to this restriction is to combine elements from active control with locally resonant metamaterial designs. The enormous potential of this approach for providing broadband control within a small footprint has been demonstrated within an earlier CASE studentship programme at the ISVR. In that programme passive and active metamaterials were produced using additive layer manufacturing techniques. The current EPSRC CASE programme will aim to take these designs further and evaluate performance within a full scale industrial environment.

If you wish to discuss any details of the project informally, please contact Prof. Steve Daley, ISVR Signal Processing and Control Group, Email: s.daley<στο>soton.ac.uk, Tel: +44 (0) 2380 59 3043.