Vibroacoustic effects of resonant sonic crystals in sound absorption

Abstract

[EN] A resonant sonic crystal made of solid elastic clamped beams is experimentally analysed in this work. The sonic crystal studied in this work has three characteristics: (i) a low filling fraction, (ii) a high frequency Band Gap and (iii) resonant scatterers. Due to the properties (i) and (ii), the sonic crystal behaves as an equivalent fluid with acoustic properties very closed to ones of the air. This means that the crystal is almost impedance matched, being the crystal transparent to the incident waves. However, the resonant elements have a resonance frequency in the range analysed in this work, introducing an absorption peak due to the resonances produced by the vibroacoustic coupling. The two microphone transfer function method is used to measure the (complex) impedance and then to evaluate experimentally the absorption coefficient of the 2D SC made of a set of parallel solid beams in the low frequency regime.