This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.The angular dependence of the transmission of sound in air through four types of 2D slit-arrays
formed of aluminium slats is explored, both experimentally and numerically. For a simple, subwavelength
periodic slit-array, it is well known that Fabry-Perot-like wave-guide resonances, supported
by the slit-cavities, hybridising with bound acoustic surface waves, result in ‘Enhanced Acoustic
Transmission’ at frequencies determined by the length, width and separation of each slit-cavity. We
demonstrate that altering the spacing or width of some of the slits to form a compound array (i.e.
an array having a basis comprised of more than one slit) results in sharp dips in the transmission
spectra, that may have a strong angular dependence. These features correspond to ‘phase resonances’,
which have been studied extensively in the electromagnetic case. This geometry allows for
additional near-field configurations compared to the simple array, whereby the field in adjacent cavities
can be out-of-phase. Several types of compound slit-array are investigated; one such structure
is optimised to minimise the effect of boundary-layer loss mechanisms present in each slit cavity,
thereby achieving a deep, sharp transmission minimum in a broad maximumThe authors would like to thank the UK Ministry of Defence’s
Defence Science and Technology Laboratorty (DSTL)
for their financial support and permission to publis
