Acoustic Resonance Research Articles

The effects of the acoustic resonance induced in the atmosphere

After strong earthquakes and volcanic eruptions, geomagnetic oscillations with frequencies of 3.5–4.0 mHz have sometimes been observed. In this paper, we theoretically study the probable cause of these phenomena, which is related to the vertical acoustic resonance arising between the Earth’s surface and the thermosphere due to the propagation of the atmospheric wave corresponding to the acoustic branch generated by surface displacements. In the plane layered model of the atmosphere and ionosphere with inclined geomagnetic field, we analyze the propagation of two-dimensional (2D) harmonic acoustic wave. The height of the reflecting atmospheric layer corresponds to the region of sharp temperature change close to the thermosphere boundary ∼80–90 km. In this case, the calculated fundamental resonant frequency is close to the frequencies of the observed oscillations. The solution of this problem is used to calculate currents and electromagnetic perturbations in the atmosphere and ionosphere. The ionospheric E-layer is considered in the thin layer approximation. In this approximation, the formulas describing the geomagnetic perturbations (GMP) in the ionosphere and on the Earth’s surface are derived. The GMP spectrum contains a sharp maximum at the frequency corresponding to the acoustic resonance. According to the calculations, close to the resonance frequency, the spectral powers of GMPs on the ground can reach 5–30 nT2/Hz, which is consistent with the results of ground-based measurements.

A mini-resonant photoacoustic sensor based on a sphere-cylinder coupled acoustic resonator for high-sensitivity trace gas sensing

This paper reports a mini-resonant photoacoustic sensor for high-sensitivity trace gas sensing. The sensor primarily contains a sphere-cylinder coupled acoustic resonator, a cylindrical buffer chamber, and a fiber-optic acoustic sensor. The acoustic field distributions of this mini-resonant photoacoustic sensor and the conventional T-type resonant photoacoustic sensor have been carefully evaluated, showing that the first-order resonance frequency of the present mini-resonant photoacoustic sensor is reduced by nearly a half compared to that of the T-type resonant photoacoustic sensor. The volume of the developed photoacoustic cavity is only about 0.8 cm3. Trace methane is selected as the target analytical gas and a detection limit of 101 parts-per-billion at 100-s integration time has been achieved, corresponding to a normalized noise equivalent absorption (NNEA) coefficient of 1.04 × 10−8 W·cm−1·Hz−1/2. The developed mini-resonant photoacoustic sensor provides potential for high-sensitivity trace gas sensing in narrow spaces.

Analysis and verification on second-order nonlinearity in radio frequency bulk acoustic wave devices employing temperature compensation films

This paper discusses the impact of SiO2/SiOF on second harmonic (H2) generation in temperature-compensated (TC) film bulk acoustic resonators (FBARs). First, two types of TC-FBARs are fabricated and their H2 behavior is compared with that of the standard FBAR. Next, the H2 characteristics of the TC layer are investigated by the use of a series of TC-FBARs where SiOF and Cr layers are placed on the outside of electrodes. The simulations agree very well with the measurements and can explain well how the H2 response changes with Cr thickness. Not only AlN but also SiOF contributes to the generation of H2 response, and H2 becomes very small at an appropriate Cr thickness. Finally, the TC-FBAR filter operating at 5.9 GHz is fabricated and its H2 response is compared with the simulation. The simulation agrees well with the experiment. It is also demonstrated that the insertion of the TC layer is effective in suppressing H2 generation.

A cancer cell nanotherapy method based on GHz film bulk acoustic resonator and nanoscale CaO2.

Sonodynamic therapy (SDT) is an emerging cancer treatment method in recent years. However, the ultrasound signal utilized for SDT is usually located at a low-frequency spectrum (<2MHz), and in the field of SDT research, few studies have focused on the exploration and development of ultrasound frequency. Studies have shown that the GHz-level ultrasound can increase cell membrane permeability and have a negligible effect on cell vitality. Herein, we reported the study of a GHz thin film bulk acoustic resonator as an ultrasound source for synergistic treatment with nanoscale calcium peroxide (CaO2). It was discovered that this ultrasound source ultimately achieved an efficient therapeutic outcome on mouse breast cancer cell line 4T1. Such GHz-level ultrasound application in SDT is of high significance to broaden the cognition and application scope of SDT.

Application of an overlay for spurious suppression of multi-layered surface acoustic wave resonators with double busbar configuration

Abstract This paper discusses the suppression of a spurious resonance called the gap mode which appears when the double busbar configuration is applied to multi-layered surface acoustic wave resonators. Two kinds of overlay structures are proposed for the gap mode mitigation. First, the use of lossy ones is studied. The results indicate that the lossy overlay can effectively mitigate the gap mode response when the viscosity is adequate. The layer thickness has a negligible impact on the mitigation. Then, the discussion is extended to the application of high-acoustic-velocity materials as the overlay. The resonance frequency of the gap mode can be moved to the upper-frequency side without affecting the main resonance by simply depositing a high-velocity overlay to the gap region. Finally, the comparison and choice of overlay materials are also studied. The results point out that Si3N4 is the optimum choice for industrial use.

Acoustic Cell Patterning for Structured Cell-Laden Hydrogel Fibers/Tubules.

Cell-laden hydrogel fibers/tubules are one of the fundamentals of tissue engineering. They have been proven as a promising method for constructing biomimetic tissues, such as muscle fibers, nerve conduits, tendon and vessels, etc. However, current hydrogel fiber/tubule production methods have limitations in ordered cell arrangements, thus impeding the biomimetic configurations. Acoustic cell patterning is a cell manipulation method that has good biocompatibility, wide tunability, and is contact-free. However, there are few studies on acoustic cell patterning for fiber production, especially on the radial figure cell arrangements, which mimic many native tissue-like cell arrangements. Here, an acoustic cell patterning system that can be used to produce hydrogel fibers/tubules with tunable cell patterns is shown. Cells can be pre-patterned in the liquid hydrogel before being extruded as cross-linked hydrogel fibers/tubules. The radial patterns can be tuned with different complexities based on the acoustic resonances. Cell viability assays after 72h confirm good cell viability and proliferation. Considering the biocompatibility and reliability, the present method can be further used for a variety of biomimetic fabrications.

The Effect of Atmospheric Acoustic Resonance Induced by Earthquakes and Volcanic Eruptions on the Ionosphere and Geomagnetic Field

The Effect of Atmospheric Acoustic Resonance Induced by Earthquakes and Volcanic Eruptions on the Ionosphere and Geomagnetic Field

Sealed-Cavity Bulk Acoustic Resonator for Subsequent Fabrication and Higher Order Mode

Sealed-Cavity Bulk Acoustic Resonator for Subsequent Fabrication and Higher Order Mode

Research on the Aerodynamic Noise Characteristics of Heat Exchanger Tube Bundles Based on a Hybrid URANS-FWH Method

This paper examines the aerodynamic noise characteristics of heat exchanger tube bundles, with the objective of exploring the frequency and directional features of noise under nonacoustic resonance conditions, to provide assistance in determining acoustic resonance. To predict the flow-induced noise of tube bundles, this study employs a hybrid URANS-FWH method. The transition SST model of URANS is used to accurately simulate the turbulent flow field and obtain precise statistical data on turbulence. The FWH equation is utilized to predict and evaluate the intensity and spectral characteristics of the tube bundle noise. The research findings indicate that the noise generated by the heat exchanger tube bundle is affected by pressure pulsations resulting from vortex motion in the deeper regions of the tube bundles. Notably, within specific frequency ranges, the noise intensity experiences a significant enhancement, potentially triggering complex modes of acoustic resonance. This resonance phenomenon poses safety concerns for equipment and threatens the wellbeing of personnel. Consequently, this study provides a solid theoretical foundation for predicting and controlling noise in heat exchanger tube bundles, offering valuable guidance for practical applications.

Modal Analysis of Combustion Chamber Acoustic Resonance to Reduce High-Frequency Combustion Noise in Pre-Chamber Jet Ignition Combustion Engines

&lt;div&gt;The notable increase in combustion noise in the 7–10 kHz band has become an issue in the development of pre-chamber jet ignition combustion gasoline engines that aim for enhanced thermal efficiency. Combustion noise in such a high-frequency band is often an issue in diesel engine development and is known to be due to resonance in the combustion chamber. However, there are few cases of it becoming a serious issue in gasoline engines, and effective countermeasures have not been established. The authors therefore decided to elucidate the mechanism of high-frequency combustion noise generation specific to this engine, and to investigate effective countermeasures. As the first step, in order to analyze the combustion chamber resonance modes of this engine in detail, calculation analysis using a finite element model and experimental modal analysis using an acoustic excitation speaker were conducted. As a result, it was found that there are two combustion chamber resonance modes in the 7–10 kHz band, both of which affect the high-frequency oscillation of the in-cylinder pressure. Both resonant modes have mode shapes that form a single nodal plane in the diametrical direction including the central axis of the cylinder, but the orientations of those nodal planes differ by 90 degrees. In addition, the two resonance frequencies are influenced by not only the bore diameter, temperature, and heat capacity ratio, but also the spatial shape of the combustion chamber. Therefore, when the piston descends and the spatial shape of the combustion chamber changes, the resonance frequencies change as well.&lt;/div&gt;

Lithium Niobate MEMS Antisymmetric Lamb Wave Resonators with Support Structures.

The piezoelectric thin film composed of single-crystal lithium niobate (LiNbO3) exhibits a remarkably high electromechanical coupling coefficient and minimal intrinsic losses, making it an optimal material for fabricating bulk acoustic wave resonators. However, contemporary first-order antisymmetric (A1) Lamb mode resonators based on LiNbO3 thin films face specific challenges, such as inadequate mechanical stability, limited power capacity, and the presence of multiple spurious modes, which restrict their applicability in a broader context. In this paper, we present an innovative design for A1 Lamb mode resonators that incorporates a support-pillar structure. Integration of support pillars enables the dissipation of spurious wave energy to the substrate, effectively mitigating unwanted spurious modes. Additionally, this novel approach involves anchoring the piezoelectric thin film to a supportive framework, consequently enhancing mechanical stability while simultaneously improving the heat dissipation capabilities of the core.

Nanoelectromechanical Control of Spin-Photon Interfaces in a Hybrid Quantum System on Chip.

Color centers (CCs) in nanostructured diamond are promising for optically linked quantum technologies. Scaling to useful applications motivates architectures meeting the following criteria: C1 individual optical addressing of spin qubits; C2 frequency tuning of spin-dependent optical transitions; C3 coherent spin control; C4 active photon routing; C5 scalable manufacturability; and C6 low on-chip power dissipation for cryogenic operations. Here, we introduce an architecture that simultaneously achieves C1-C6. We realize piezoelectric strain control of diamond waveguide-coupled tin vacancy centers with ultralow power dissipation necessary. The DC response of our device allows emitter transition tuning by over 20 GHz, combined with low-power AC control. We show acoustic spin resonance of integrated tin vacancy spins and estimate single-phonon coupling rates over 1 kHz in the resolved sideband regime. Combined with high-speed optical routing, our work opens a path to scalable single-qubit control with optically mediated entangling gates.

Nonlinear supersonic flutter of a composite panel backed by an acoustic cavity with finite-amplitude sound waves

In this paper, an implicit partitioned fluid-structure-acoustic interaction method is presented for predicting nonlinear aeroelastic response of an elastic composite laminated panel backed by an acoustic cavity and subject to a supersonic flow. The method is formulated in an arbitrary Lagrangian-Eulerian framework based on the unsteady Navier-Stokes equations for the supersonic flow, a geometrical nonlinear dynamics model for the composite laminated panel, and the nonlinear Westervelt equation for the finite-amplitude sound waves in cavity. A theoretical fluid-structure-acoustic model of the supersonic panel is proposed for validating the present numerical method, in which the nonlinear structural model of the panel, the first-order piston aerodynamics model of the supersonic flow and the nonlinear sound wave model of the cavity are coupled in a monolithic manner. It is found that cavity acoustic resonance can appear in the case a vibration mode of the panel coalescing with an acoustic mode of the cavity. Several new physical features of nonlinear acoustic resonance have been discovered, such as the presence of shock wave with high pressure gradients travelling along the resonant cavity in axial direction and the presence of higher-order harmonic wave components, which emphasize a nonlinear acoustic wave model of the cavity must be used to fully characterize these phenomena. In addition, the nonlinearity of the standing wave is quantitatively related to the acoustic modes by means of a proper orthogonal decomposition analysis.

Serially connected strip-type acoustic wave resonator using X-40°Y LiNbO3 (XSAR)—feasibility study using macro model

This work presents a new serially connected strip-type acoustic resonator using X40°Y-LiNbO3 (LN) (XSAR). The proposed design is composed of a serial of strip-type bulk acoustic wave resonators connected together. The volume between two strips is penetrated through to eliminate the spurious response and enhance quality (Q) factor. The Euler angle (90°, 90°, 40°) of LN is optimized to obtain the maximal piezoelectric constant e 34, which determines the coupling factor of shear mode of the resonator. Simulation results show that the new design is superior in terms of impedance ratio (Z-ratio) and bandwidth (BW) and exhibits the largest BW of 32% ever reported. The slow shear mode spurious response is successfully removed by the proposed penetrated structure combined with narrow strip. Furthermore, the device was prototyped in macro scale using 350 μm thick LN, by which the ultra-wide BW and potentially good performance in HF were confirmed.

A physical picture for the acoustic resonant drag instability

ABSTRACT Mixtures of gas and dust are pervasive in the Universe, from active galactic nuclei (AGNs) and molecular clouds to protoplanetary discs. When the two species drift relative to each other, a large class of instabilities can arise, called ‘resonant drag instabilities’ (RDIs). The most famous RDI is the streaming instability, which plays an important role in planet formation. On the other hand, acoustic RDIs, the simplest kind, feature in the winds of cool stars, AGNs, or starburst regions. Unfortunately, owing to the complicated dynamics of two coupled fluids (gas and dust), the underlying physics of most RDIs is mysterious. In this paper, we develop a clear physical picture of how the acoustic RDI arises and support this explanation with transparent mathematics. We find that the acoustic RDI is built on two coupled mechanisms. In the first, the converging flows of a sound wave concentrate dust. In the second, a drifting dust clump excites sound waves. These processes feed into each other at resonance, thereby closing an unstable feedback loop. This physical picture helps decide where and when RDIs are most likely to happen, and what can suppress them. Additionally, we find that the acoustic RDI remains strong far from resonance. This second result suggests that one can simulate RDIs without having to fine-tune the dimensions of the numerical domain.

Compact and wideband nanoacoustic pass-band filters for future 5G and 6G cellular radios

Over recent years, the surge in mobile communication has deepened global connectivity. With escalating demands for faster data rates, the push for higher carrier frequencies intensifies. The 7–20 GHz range, located between the 5G sub-6 GHz and the mm-wave spectra, provides an excellent trade-off between network capacity and coverage, and constitutes a yet-to-be-explored range for 5G and 6G applications. This work proposes a technological platform able to deliver CMOS-compatible, on-chip multi-frequency, low-loss, wide-band, and compact filters for cellular radios operating in this range by leveraging the micro-to-nano scaling of acoustic electromechanical resonators. The results showcase the first-ever demonstrated low insertion loss bank of 7 nanoacoustic passband filters in the X-band. Most of the filters showcase fractional bandwidths above 3% and sub-dB loss per stage in an extremely compact form factor, enabling the manufacturing of filters and duplexers for the next generation of mobile handsets operating in the X-band and beyond.

Cavity-enhanced photoacoustic dual-comb spectroscopy

Photoacoustic dual-comb spectroscopy (DCS), converting spectral information in the optical frequency domain to the audio frequency domain via multi-heterodyne beating, enables background-free spectral measurements with high resolution and broad bandwidth. However, the detection sensitivity remains limited due to the low power of individual comb lines and the lack of broadband acoustic resonators. Here, we develop cavity-enhanced photoacoustic DCS, which overcomes these limitations by using a high-finesse optical cavity for the power amplification of dual-frequency combs and a broadband acoustic resonator with a flat-top frequency response. We demonstrate high-resolution spectroscopic measurements of trace amounts of C2H2, NH3 and CO in the entire telecommunications C-band. The method shows a minimum detection limit of 0.6 ppb C2H2 at the measurement time of 100 s, corresponding to the noise equivalent absorption coefficient of 7 × 10−10 cm−1. The proposed cavity-enhanced photoacoustic DCS may open new avenues for ultrasensitive, high-resolution, and multi-species gas detection with widespread applications.

Flexible Film Bulk Acoustic Wave Filter Based on Poly(vinylidene fluoride-trifluorethylene).

Poly(vinylidene fluoride-trifluorethylene) (P(VDF-TrFE)) has promising potential applications in radio-frequency filters due to their excellent piezoelectric properties, flexibility, and stability. In this paper, a flexible film bulk acoustic wave filter is investigated based on P(VDF-TrFE) as piezoelectric film. A new method based on three-step annealing is developed to efficiently remove the porosity inside the P(VDF-TrFE) films so as to improve its properties. The obtained film achieved high β-phase content beyond 80% and a high piezoelectric coefficient of 27.75 pm/V. Based on the low porosity β-phase films, a flexible wide-band RF filter is designed, which consists of a bulk acoustic wave resonator and lumped inductor-capacitor elements as a hybrid configuration. The resonator sets the filter's center frequency, while the lumped LC-based matching network extends the bandwidth and enhances out-of-band rejection. The testing results of the proposed wide-band filter show its good performance, with 12.5% fractional bandwidth and an insertion loss of 3.1 dB. To verify the possibility of folding and stacking the flexible bulk acoustic wave devices for high-density multi-filter integration in MIMO communication, bending tests of the filter are also conducted with the bending strain range up to 5500 με. The testing results show no noticeable performance degradation after four bending cycles. This work demonstrates the potential of β-phase P(VDF-TrFE) bulk acoustic wave filters to expand the scope of future flexible radio-frequency filter applications.

Influence of Homo- and Hetero-Junctions on the Propagation Characteristics of Radially Propagated Cylindrical Surface Acoustic Waves in a Piezoelectric Semiconductor Semi-Infinite Medium

This paper theoretically investigates the influence of homo- and hetero-junctions on the propagation characteristics of radially propagated cylindrical surface acoustic waves in a piezoelectric semiconductor semi-infinite medium. First, the basic equations of the piezoelectric semiconductor semi-infinite medium are mathematically derived. Then, based on these basic equations and the transfer matrix method, two equivalent mathematical models are established concerning the propagation of radially propagated cylindrical surface acoustic waves in this piezoelectric semiconductor semi-infinite medium. Based on the surface and interface effect theory, the homo- or hetero-junction is theoretically treated as a two-dimensional electrically imperfect interface in the first mathematical model. To legitimately confirm the interface characteristic lengths that appear in the electrically imperfect interface conditions, the homo- or hetero-junction is equivalently treated as a functional gradient thin layer in the second mathematical model. Finally, based on these two mathematical models, the dispersion and attenuation curves of radially propagated cylindrical surface acoustic waves are numerically calculated to discuss the influence of the homo- and hetero-junctions on the dispersion and attenuation characteristics of radially propagated cylindrical surface acoustic waves. The interface characteristic lengths are legitimately confirmed through the comparison of dispersion and attenuation curves calculated using the two equivalent mathematical models. As piezoelectric semiconductor energy harvesters usually work under elastic deformation, the establishment of mathematical models and the revelation of physical mechanisms are both fundamental to the analysis and optimization of micro-scale surface acoustic wave resonators, energy harvesters, and acoustic wave amplification based on the propagation of surface acoustic waves.

Three-dimensional acoustic resonators for massively scalable spectral processors

Three-dimensional acoustic resonators for massively scalable spectral processors