Cereal straws are one of the oldest biomaterials in use and known for remarkable acoustic performances in sound absorption. The research team around Huang et al. (2019) used 3D-printed samples to research a theoretical concept to explain the extraordinary sound absorption abilities.
The results recently published in “Scientific Reports” under the title “3D-printed sound absorbing metafluid inspired by cereal straws” shows that the internal structure of cereal straws is made of nodes. In the form of a straw ball, negative acoustic effects are achieved when the straws of a straw ball is cut on either side of a node. The research team tested large spectral bandgaps and slow sound regimes experimentally from impedance tube measurements on an idealized 3D-printed structure. They found that the metafluid structure combines visco-thermal diffusion with strong wave dispersion arising from quarter-wavelength resonances within straws. Perfect sound absorption is achieved at wavelengths 13 times larger than the thickness of the metafluid layer, and slow sound entails an increased density of states, causing a cascade of high absorption peaks. This research could lead to the use of cereal straws as a cheap acoustic bio-metamaterial.
Source:
Huang, W., Schwan, L., Romero-García, V., Génevaux, J. M., & Groby, J. P. (2019). 3D-printed sound absorbing metafluid inspired by cereal straws. Scientific reports, 9(1), 8496.
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