Experimental Investigation of an Acoustic Metamaterial Barrier Design Composed of a Square Prism Within a Hexagonal Recess

Abstract

This paper presents an experimental investigation of an acoustic barrier composed out of an acousticmetamaterial unit cell. The design of the unit cell consists of a square prism, acting as a resonator,within a hexagonal recess manufactured out of a single material. Two materials were used tomanufacture the unit cell: PolyMide Polycarbonate and Polylite Polylactic Acid. The acousticperformance of the unit cell was quantified for both materials using the acoustic absorptioncoefficient and acoustic transmission loss values for frequencies between 100 Hz and 5,000Hz. Theexperimental results indicate that the design reduced the peak absorption coefficient for bothmaterials while also introducing two additional peaks at around 1,500 Hz and at 4,000 Hz. Changesto the absorption coefficient values were observed for frequencies above 1,000 Hz while minimalchanges were observed for frequencies below 1,000 Hz. These results indicate that the proposeddesign, is able to widen the effective frequency band, or stop band for acoustic absorption forfrequencies above 1,000 Hz compared to the absorption coefficient of the material. The experimentalresults also indicate that the design increases the peak transmission loss by about 7 dB at 4,000 Hz.For sounds below 3,000 Hz, the design will only change the transmission loss by about 3 dB forfrequencies between 100 Hz to 3,000 Hz. These results indicate that the acoustic metamaterial design,consisting of resonator in a recess manufactured out of a single material, is able to broaden theeffective frequency range for sound absorption for frequencies between 1,000 Hz and 4,000 Hz andat increasing the transmission loss values for frequencies between 3,000 Hz and 5,000 Hz. It can beconcluded that the resonator in recess metamaterial design, manufactured out of a single material,can be used to increase the stop band for acoustic absorption for frequencies above 1,000 Hz and toincrease the transmission loss for frequencies above 3,000 Hz.

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Free vibration analysis of metamaterial functionally graded plates with quasi-zero stiffness resonators

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