New Publication: The acoustic phase resonances and surface waves supported by a compound rigid grating

Congratulations to Joseph Beadle, 4th year PGR in the EPSRC CDT in Metamaterials, for his latest publication on ‘The acoustic phase resonances and surface waves supported by a compound rigid grating‘, published in Nature’s Scientific Reports.

Abstract

We study the radiative and bound acoustic modes supported by a rigid grating formed of three same-depth, narrow grooves per unit cell. One of the grooves is twice the width of the other two, forming a ‘compound’ grating. The structure supports so-called ‘phase’ resonances where the phase difference of the pressure field between the grooves on resonance varies by multiples of π. We explore the dispersion of these modes experimentally by monitoring the specularly reflected signal as a function of the angle of incidence. In addition, by near-field excitation, the dispersion of the non-radiative surface modes has been characterised. Our results are compared with the predictions of a finite element method model.

Figure: Schematic (not to scale) of the experimental setup, consisting of a speaker at the focus of a collimating mirror giving a plane wave incident onto the sample, the reflected signal being then focused by a second mirror onto the microphone. The speaker and microphone are placed below the central plane of the mirrors and sample such that they do not directly impede the acoustic beams. Here, α = 90° − θ.

 

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