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Dr Joseph Beadle


Supervisors: Prof.Roy Sambles and Prof. Alastair Hibbins


The ablity to control acoustic waves on surfaces has gathered much interested recently. Acoustic waves which are bound to a periodically-structured surface are know as acoustic surface waves, these surface bound wave exist in the air above an acoustically-rigid material. The way in which these surface waves will propagate over the surface is critically dependent on the structure, some structure have band-gap between certain frequencies which forbids acoustic surface waves from existing. The symmetry of the surface also plays an important role in the characteristics of these waves, for example one such symmetry named glide symmetry which shows that the structure will be the same if it is translated half its period and mirrored on the glide plane, the specific symmetry allows for a zero-bandgap to exist at the 1st Brillouin zone boundary due to 2 degenerate modes existing, this alows the surface wave to exist ove a broadband of frequencies without any band gaps, which can also have the feature of constant group velocity. For my project I am investing these metasurfaces. Such effects as constant broadband group velocity if labyrinthine structures, near 100% absportion of incident radiation due to a special compound grating have been investigated. We investigate these waves by finite element modelling and experiments. Using these two methods we can characterise the dispersions of the surfaces. Other interests include maximising the effect of the thermoviscous losses by changing the shape of acoustic resonantors, coupling between surface waves and elastic media in air.