Reduction of specular reflections in aerospace applications with sonic crystals
Sonic crystals (SCs) are artificial structures made of periodic arrangements of rigid scatterers embedded in a fluid host medium. One of the most known properties of SCs is the presence of band gaps, ranges of frequencies in which the sound waves are not propagated beyond the system due to destructive interference of the sound waves reflecting in the elements.
SCs also present important diffusive properties, reflecting the sound waves in non-specular directions. For this reason, they have been studied as a possible solution to be applied in aerospace applications, since big part of the acoustic load suffered by the spacecraft comes from the specular reflections in the bottom of the launch pad.
Different periodic distributions have been numerically and experimentally studied, and the diffusion coefficient of each of them has been characterized in sub-scale systems by researchers of the Universitat Politècnica de València (Spain).
The results of the study show that SCs can reduce broadband noise levels at the location of an acoustic source due to the reduction of specular reflection and the deflection of acoustic waves in other directions.
Full article available in the journal Aerospace Science and Technology: https://www.sciencedirect.com/science/article/abs/pii/S127096381731043X?via%3Dihub.