Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2003.09059

Ultra-slow sound in non-resonant meta-aerogel

Ai Du·Yuhan Xie·Yan Li·Yongdong Pan·Guangming Wu·Bin Zhou
View original source ↗Read source document ↗Export metadata ↓

Abstract

The manipulation of sound with acoustic metamaterials is a field of intense research, where interaction via resonance is a common application despite the significant disadvantages. We propose a novel procedure for introducing well-designed coupling interfaces with a cell size of less than 10 nm into an ultra-soft porous medium, to prepare a meta-aerogel, where the sound propagation is significantly delayed in a non-resonant mode. The resultant sound velocity is shown as a scaling law with the mass density and the mass fraction ratio of the components, in accordance with our analytical model. We have prepared a meta-aerogel with the slowest sound velocity of 62 m/s. To the best of our knowledge, this is the lowest value in compact solid materials, with a prospect of further slowing down by our procedure. The development of such meta-aerogels can facilitate key applications in acoustic metamaterials intended to employ non-resonant type slow sound (or phase delay). Examples of the latter include deep subwavelength meta-surface and other focused imaging or transformation acoustics that require a high contrast of sound velocity.

Explore related subjects

physics.app-phcond-mat.mtrl-sci

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Ai Du, Yuhan Xie, Yan Li, Yongdong Pan, Guangming Wu, Bin Zhou. 2020-03-20. Ultra-slow sound in non-resonant meta-aerogel. https://arxiv.org/abs/2003.09059

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

RCS angular control with gradient metasurfaces: design and measurement

This letter proposes the design and measurement of a periodic metasurface that achieves anomalous reflection with reduced RCS in a given parasitic direction. A previous study proposed a semi-analytical model to predict the RCS behavior of such a metasurface. However, this first study did not include any experimental exploration to verify the theoretical results. To complete this study, this work presents an experimental validation of the proposed design, with a focus on manufacturing and measurement issues. The synthesis, design specifications, fabrication method and experimental setup are presented and discussed. Measurement results are also examined in detail, highlighting some limitations in metasurfaces RCS measurements. The proposed metasurface effectively achieves the predicted RCS level reduction in the considered parasitic direction. The agreement between simulation and experimental results demonstrates the accuracy of the modelling and the efficiency of the optimisation procedure.

physics.app-ph↗
arXiv2026

Maximum-Power-Transfer Power Coordinates for Fully Coupled Multiport Thévenin Sources

A power-normalized scattering representation is developed at a fixed frequency for a passive linear time-invariant multiport load driven by a fully coupled multiport Thévenin source. The source is obtained by reducing, at the load reference planes, an independent-source network whose suppressed internal impedance is passive, together with an intervening passive matching network. No diagonal-reference, uncoupled-source-channel, reciprocity, or commutation assumption is required. With $R_s=\mathrm{Herm}\{Z_s\}\succ\mathbf{0}$, completing the square in accepted power identifies the available-power current and motivates the coordinates $\mathbf{a}=\frac12R_s^{-1/2}(\mathbf{V}+Z_s\mathbf{I})$, $\mathbf{b}=\frac12R_s^{-1/2}(\mathbf{V}-Z_s^H\mathbf{I})$. They satisfy $\|\mathbf{a}\|_2^2-\|\mathbf{b}\|_2^2=\Re\{\mathbf{I}^H\mathbf{V}\}$ and yield $\mathbf{S}=R_s^{-1/2}(Z_{load}-Z_s^H)(Z_{load}+Z_s)^{-1}R_s^{1/2}$. An exact operator identity establishes passivity--contractivity equivalence and gives excitation-specific, reachable-subspace, and complete conjugate-matching conditions. On the physically reachable incident subspace, singular values characterize the best- and worst-case source-normalized port-reflection TARC, while a restricted Frobenius norm gives the basis-averaged squared TARC. Equal-magnitude phase-only control is formulated separately as a constant-modulus problem, with generator-side constraints mapped through the coupled source network before power normalization. For antenna loads and excitations with $P_{acc}>0$, $P_{rad}/P_{av}=η_{rad}(1-\mathrm{TARC}^2)$, so terminal scattering data alone do not determine radiation efficiency. When $R_s$ is singular, finite available power exists exactly for $\mathbf{E}\in\mathrm{range}(R_s)$, and the construction applies on the positive-resistance support.

physics.app-ph↗
arXiv2026

Bimorph Lithium Niobate Thickness-Shear Overtone Film Bulk Acoustic Resonator

High quality factor ($Q$) and overtone operation enable narrow-linewidth acoustic devices with multiple discrete frequencies in a single cavity. Maintaining both high $Q$ and sufficient electromechanical coupling at higher mode orders remains challenging. Here, we demonstrate a bimorph periodically poled piezoelectric film (P3F) lithium niobate (LN) platform for high-order thickness-shear (TS) overtone excitation. The device comprises a bonded 80-$μ$m-thick single-crystal X-cut LN bimorph with opposite polarizations, patterned top and floating bottom electrodes, and a suspended air cavity. The P3F configuration mitigates charge cancellation from the alternating stress distribution of higher-order TS modes, enabling measurable coupling across a broad sequence of overtones. The thick LN acoustic cavity and increasingly confined high-order mode profiles support low-loss operation. Measured TS overtones extend to 1.75 GHz. At room temperature, representative overtones at 0.77 and 0.89 GHz exhibit 3-dB $Q$ values of 11,338 and 11,917, corresponding to $fQ$ products of $8.74\times10^{12}$ and $1.06\times10^{13}$ Hz, respectively. Cooling from 297 to 12 K systematically enhances $Q$, yielding a peak 3-dB $Q$ of 20,507 at 779 MHz and a maximum $fQ$ product of $1.98\times10^{13}$ Hz at 1.379 GHz. These results establish bimorph P3F LN as a promising platform for high-$Q$, frequency-scalable micro-acoustic resonators in the sub-GHz and low-GHz regimes.

physics.app-ph↗