• Home

Euronoise 2018: 1.1 - Acoustic and Elastic Metamaterials

Lecture: 3D printed acoustic metamaterial sound absorbers using functionally-graded sonic crystals

Author(s): Guild Matthew, Rothko Michael, Sieck Caleb, Rohde Charles, Orris Gregory

Acoustic metamaterials have been utilized in recent years to achieve extreme acoustic properties, which have enabled enhanced acoustic characteristics and performance beyond the bounds of traditional materials. In this paper, a thin functionally-graded acoustic metamaterial sound absorber is presented and discussed. While sound absorbers are traditionally limited to an absorption coefficient of 0.5 or less, in this paper it is shown that the proposed design can attain an absorption coefficient near 1. To do this, the acoustic metamaterial sound absorber must simultaneous possess near zero reflectance and transmittance over a given frequency band, thereby resulting in an absorption coefficient near unity. To achieve this, the acoustic metamaterial structure consists of a multilayer arrangement of an interwoven sonic crystal lattice with varying filling fractions, backed by a thin elastic coating that acts as a flexural acoustic element. The overall thickness of the sound absorber is about one tenth of the wavelength in air, and it was fabricated using additive manufacturing (3D printing) with a thermoplastic polyurethane (TPU). Samples were fabricated and acoustically tested in an air-filled acoustic impedance tube to provide absorption and effective acoustic properties. A theoretical formulation for the effective acoustic properties of the interwoven sonic crystal lattice was used to guide the design process, and excellent agreement was found between measured and theoretically predicted results. A range of filling fractions and thicknesses were tested to verify the fabrication process and robustness of the modeling, and both were found to be in excellent agreement. [Work supported by the Office of Naval Research.]

Download the full paper

Corresponding author

Name: Dr Matthew Guild

e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Country: United States