Programmable bulk modulus in acoustic metamaterials composed of strongly interacting active cells

Abstract

Active acoustic metamaterials are one path to acoustic properties difficult to realize with passive structures, especially for broadband applications. Here, we experimentally demonstrate a 2D metamaterial composed of coupled sensor-driver unit cells with effective bulk modulus ([Formula: see text]) precisely tunable through adjustments of the amplitude and phase of the transfer function between pairs of sensors and drivers present in each cell. This work adopts the concepts of our previous theoretical study on polarized sources to realize acoustic metamaterials in which the active unit cells are strongly interacting with each other. To demonstrate the capability of our active metamaterial to produce on-demand negative, fractional, and large [Formula: see text], we matched the scattered field from an incident pulse measured in a 2D waveguide with the sound scattered by equivalent continuous materials obtained in numerical simulations. Our approach benefits from being highly scalable, as the unit cells are independently controlled and any number of them can be arranged to form arbitrary geometries without added computational complexity.

Application of machine learning on the design of acoustic metamaterials and phonon crystals: a review

“…Sound absorption coefficient (α) is a physical quantity that measures the sound absorption performance of acoustic materials and can reflect the strength of the material's sound absorption ability. Sound absorption coefficient calculation formula (2)(3), where E i is the incident sound energy; E r is reflected sound energy,…”

“…artificially designed and optimized to achieve extraordinary physical properties that natural materials do not possess, such as single negativity [1][2][3] (negative mass or negative modulus) or double negativity [4][5][6] (negative mass and modulus), negative refraction [7,8], etc, enabling special wave propagation and wave control of sound waves. These unique properties make AMs have wide-ranging applications prospects in areas such as sound wave control [9,10], acoustic invisibility [11][12][13], and acoustic imaging [14][15][16].…”

Tunable, reconfigurable, and programmable acoustic metasurfaces: A review

“…In comparison with passive AMs that have a fixed functionality once fabricated, the implementation of active elements affords great flexibility and convenience in tuning their responses with reconfigurable electronic circuits. The most common application of such an approach is in membrane-type AMs where, depending on their type and nature, properties such as surface tension can be easily tuned by applying an external voltage (Cheng et al, 2018;Shen et al, 2019;Zhai et al, 2019;Akl and Baz, 2021;Zhang et al, 2021;Kovacevich and Popa, 2022;Peng et al, 2022). Zhang et al (2016), (Zhang et al, 2016).…”

Scalable active acoustic metamaterials with programmable bulk modulus and mass density tensor

“…To address this, we previously developed a polarized source model for arbitrary active acoustic metamaterial geometries in 2D that explicitly relates the programmed gains to the effective bulk modulus and mass density tensor [14]. We applied that model to an experimental metamaterial of programmable bulk modulus [15], and now in this work we expand to an experimental metamaterial of both programmable bulk modulus and mass density.…”