Broadband low-frequency sound isolation by lightweight adaptive metamaterials

Abstract

Blocking broadband low-frequency airborne noises is highly desirable in lots of engineering applications, while it is extremely difficult to be realized with lightweight materials and/or structures. Recently, a new class of lightweight adaptive metamaterials with hybrid shunting circuits has been proposed, demonstrating super broadband structure-borne bandgaps. In this study, we aim at examining their potentials in broadband sound isolation by establishing an analytical model that rigorously combines the piezoelectric dynamic couplings between adaptive metamaterials and acoustics. Sound transmission loss of the adaptive metamaterial is investigated with respect to both the frequency and angular spectrum to demonstrate their sound-insulation effects. We find that efficient sound isolation can indeed be pursued in the broadband bi-spectrum for not only the case of the small resonator's periodicity where only one mode relevant to the mass-spring resonance exists, but also for the largeperiodicity scenario, so that the total weight can be even lighter, in which the multiple plate-resonator coupling modes appear. In the latter case, the negative spring stiffness provided by the piezoelectric stack has been utilized to suppress the resonance-induced high acoustic transmission. Such kinds of adaptive metamaterials could open a new approach for broadband noise isolation with extremely lightweight structures.

Adaptive metamaterials for broadband sound absorption at low frequencies

“…In this case, the stack with shunting circuits behaves like an elastic spring whose effective stiffness varies with the frequency, as governed by equation (5). In previous studies, the dispersive stiffness of the stack has been used to trace adaptively the high transmission-loss trajectory for the broadband sound insulation [29]. In the present study, the stack is expected to serve the broadband sound absorption.…”

Improved electrical performance of a sol–gel IGZO transistor with high-k Al2O3 gate dielectric achieved by post annealing

“…The hysteresis windows of the two capacitors were also very different, where the non-annealed and annealed capacitors provided respective values of 0.67 and 0.36. The suppression in C–V hysteresis is considered to have arisen from the improved interface quality [21]. Generally, the hysteresis in the C–V measurement at a high frequency (1 MHz) is induced by a charge trap near the interface [21].…”

Mutual Inductance and Coupling Effects in Acoustic Resonant Unit Cells

“…Therefore, design of the broadband AMMs is very important. One path is to combine the different sized resonant cells in a group to achieve multiband and/or broadband AMMs, in which each cell exerts its function and oscillates in its local resonant frequency band, and the superposition of the local resonance will produce broadband effects [19,36,37,38,39]. By coupling split hollow spheres (SHSs) with different geometry sizes, a multiband and broadband AMM with negative moduli can be realized [19].…”