Acoustic metamaterial panels for sound attenuation in the 50-1000 Hz regime

We show experimentally that thin membrane-type acoustic metamaterials can serve as a total reflection nodal surface at certain frequencies. The small decay length of the evanescent waves at these frequencies implies that several membrane panels can be stacked to achieve broad-frequency effectiveness. We report the realization of acoustic metamaterial panels with thickness < 15 mm and weight < 3 kg/m(2) demonstrating 19.5 dB of internal sound transmission loss (STL) at around 200 Hz, and stacked panels with thickness < 60 mm and weight < 15 kg/m(2) demonstrating an average STL of >40 dB over a broad range from 50 to 1000 Hz.