3D-printed sound absorbing metafluid inspired by cereal straws

Area of Science:

• Acoustics
• Materials Science
• Biomaterials

Background:

• Cereal straws have a long history as building materials, recognized for their sound absorption capabilities.
• Traditional uses overlook the internal nodal structure of straws, which can be leveraged for advanced acoustic properties.

Purpose of the Study:

• To investigate the acoustic properties of cereal straws, specifically focusing on the impact of their internal nodal structure.
• To explore the potential of straw-based structures as acoustic metafluids.

Main Methods:

• Theoretical prediction of acoustic bulk modulus and wave dispersion using metafluid concepts.
• Modeling quarter-wavelength resonances within straw structures.
• Experimental validation using impedance tube measurements on a 3D-printed model.

Main Results:

• Straw balls, when cut around nodes, exhibit a negative acoustic bulk modulus.
• The metafluid demonstrates strong wave dispersion due to quarter-wavelength resonances.
• Large spectral bandgaps and slow sound regimes were theoretically predicted and experimentally supported.
• Perfect sound absorption was achieved at wavelengths significantly larger than the material thickness.

Conclusions:

• The unique nodal structure of cereal straws can be engineered into effective acoustic metafluids.
• These bio-inspired materials offer potential for high-performance, low-cost acoustic applications.
• Cereal straws can be repurposed as sustainable and affordable acoustic bio-metamaterials.