Frequency Acoustic Waves Research Articles

Audible and infrasonic waves generated during the 2022 Hunga eruption: Observations from across Aotearoa New Zealand

The 15 January 2022 eruption of Hunga volcano (Kingdom of Tonga) featured one of the most powerful blasts in recent history, generating atmospheric acoustic phenomena observed around the world. Here we examine seismo-acoustic data of the eruption from across Aotearoa New Zealand, host of the densest network of seismo-acoustic sensors in the south-west Pacific. We find clear evidence for two wavepackets of audible acoustics generated by the eruption propagating north-to-south across Aotearoa New Zealand. Celerities estimated from manually picked arrival times indicate that each wavepacket was likely induced by nonlinear phenomena during the passage of Lamb and Pekeris waves, the latter an atmospheric resonance mode not observed prior to the eruption of Hunga volcano. We also highlight results from array processing across a large scale acoustic network, where we successfully detect and estimate backazimuths for coherent low frequency acoustic waves across a maximum aperture of 11 km. The observations presented here provide a new dataset for developing novel techniques for modelling and monitoring of rare atmospheric acoustic phenomena.

Numerical investigation on the liquid jet and the dynamics of the near-wall cavitation bubble under an acoustic field

The dynamics of the near-wall cavitation bubble in an acoustic field are the fundamental forms of acoustic cavitation, which has been associated with promising applications in ultrasonic cleaning, chemical engineering, and food processing. However, the potential physical mechanisms for acoustic cavitation-induced surface cleaning have not been fully elucidated. The dynamics of an ultrasonically driven near-wall cavitation bubble are numerically investigated by employing a compressible two-phase model implemented in OpenFOAM. The corresponding validation of the current model containing the acoustic field was performed by comparison with experimental and state-of-the-art theoretical results. Compared to the state without the acoustic field, the acoustic field can enhance the near-wall bubble collapse due to its stretching effect, causing higher jet velocities and shorter collapse intervals. The jet velocity in the acoustic field increases by 80.2%, and the collapse time reduces by 40.9% compared to those without an acoustic field for γ = 1.1. In addition, the effects of the stand-off distances (γ), acoustic pressure wave frequency (f), and initial pressure (p*) on the bubble dynamic behaviors were analyzed in depth. The results indicate that cavitation effects (e.g., pressure loads at the wall center and the maximal bubble temperature) are weakened with the increase in the frequency (f) owing to the shorter oscillation periods. Furthermore, the maximum radius of bubble expansion and the collapse time decrease with increasing f and increase with increasing p*. The bubble maximum radius reduces by 12.6% when f increases by 62.5% and increases by 20.5% when p* increases by 74%.

Monitoring the sonochemical field: A critical review of chemical dosimetry methods

AbstractSonochemistry is a fascinating field that has drawn considerable interest from researchers across different disciplines. One of the key challenges in this field is the accurate characterization of the sonochemical field, which is crucial for understanding the underlying mechanisms and optimizing the process. To address this challenge, researchers have developed various monitoring methods that allow them to measure key parameters such as the intensity, frequency, and distribution of acoustic waves in the sonoreactor. In this review, we focus on the chemical dosimetry techniques that are commonly used for sonochemical monitoring. These techniques have been extensively studied in the literature and are known for their reliability and accuracy. However, as we will see, the performance of these techniques can vary depending on the chemical nature of the probing species and the experimental conditions, highlighting the need for a careful selection and calibration of the monitoring method. We begin by discussing the principles of chemical dosimetry in sonochemistry and how these methods can be used to measure key sono‐acoustic parameters. We then provide a detailed analysis of the various dosimetry techniques, including their advantages, limitations, and applicability under different operating conditions. In summary, our review serves as a valuable resource for researchers seeking to optimize their sonochemical experiments and contribute to the advancement of this fascinating field.

Combustion and extinction characteristics of an ethanol pool fire perturbed by low–frequency acoustic waves

To study combustion and extinction characteristics of flames perturbed by acoustic waves, the evolution of the shape of the pool fire, mass loss rate (ma′) of fuel, and mechanisms of extinction of the flames under acoustic perturbations were studied. Moreover, based on parameters of combustion characteristics of flames, parametric models of ma′ and flame extinction were developed. The research results demonstrate that the shapes of unperturbed flames change during combustion, however, when perturbed by acoustic waves, the flame shapes become irregular and the flame fronts become disorderly. Compared with the combustion of unperturbed flames, ma′ is increased under acoustic perturbation. There are upper and lower limits for the change of ma′, so the models of upper and lower limits of ma′ in the concentrated area were established. Low–frequency acoustic waves tend to extinguish the pool fire, and the increased distance of acoustic response and acoustic source power can promote flame extinction. A linear relationship between flame extinction and acoustic frequency was semi-quantitatively characterized by a modified Damköhler (Da*) number. Based on the critical oscillation–induced displacement for extinguishing a pool fire, local acoustic parameters were characterized, and a critical model for local displacement during the extinction of the pool fire was established.

Simultaneous Protein Adsorption and Viscosity Measurement using Micropillar-Enhanced Acoustic Wave (μPAW) Device for Pharmaceutical Applications

At the early stages of drug development, the amount of drug materials is rather limited. In this case, viscosity measurement is often postponed to the later stages, where grams of proteins can be produced. Therefore, it is necessary to develop a viscometer capable of measuring the viscosity with high accuracy while requiring low sample volume. This study presents a novel viscosity measurement technique based on measuring the resonance frequency and motional resistance of a micropillar-enhanced acoustic wave (μPAW) device. The μPAW was developed by fabricating micropillars on the quartz crystal microbalance substrate in order to achieve ultra-high sensitivity, thanks to a unique coupling between the micropillar and the resonator. The experimental measurements demonstrated a nonlinear relationship between the density and viscosity of the fluid and the response of μPAW. A calibration correlation was developed using the response of μPAW in aqueous glycerol and sucrose solutions. The measurements were then extended using high-concentration BSA solutions as the model of protein solution. The main advantage of the μPAW device in this work over other viscometers is the ability to simultaneously measure solution viscosity and protein adsorption on the surface. This is a huge step forward in the development of sensing systems for the pharmaceutical industry, where real-time sensing of target biological proteins and measuring the viscosity of a solution is required.

Influence of confined acoustic phonons on the acousto-electric field in doped semiconductor superlattices

By using a quantum kinetic equation for electrons, the expression of the acoustoelectric field under the influence of confined acoustic phonons in doped semiconductor superlattices (DSSL) is obtained. From these expressions, the acousto-electric field depends on temperature, acoustic wave frequency, Fermi energy level, doped concentration, and quantum number m characterizing the phonons confinement. The results are numerically calculated for the GaAs:Be/GaAs:Si DSSL and show that the appearance of phonons confinement makes the acousto-electric field value become different than the cases of unconfined phonons.

LUFT: A low-frequency ultrasound tomography system designed for lung imaging.

Pulmonary imaging with ultrasound in the conventional MHz range suffers from significant artifacts, as the high frequency acoustic waves primarily reflect off of the lung pleura with little to no penetration through the lung tissue. Furthermore, B-mode ultrasound images are difficult to interpret and require a skilled technician to obtain. Motivated by the finding that acoustic frequencies in the kHz penetrate lung tissue, a low-frequency tomographic ultrasound system is presented. A Verasonics Vantage 64 low-frequency ultrasound system is programmed to work with a novel low-frequency Tonpilz transducers set arranged in a circular array on a belt. After signal processing, a time-of-flight (TOF) tomographic reconstruction algorithm with refraction correction is applied to estimate the sound speed in the plane of the transducer array. Data were collected on experimental phantoms made of ballistic gel containing targets of varying sound speeds, and reconstructions TOF were computed. Results demonstrate that the low-frequency ultrasound tomography system effectively detects targets in an experimental phantom with the ability to resolve multiple targets and distinguish between targets of high and low sound speed compared to the background medium.

Sensitivity-Adjustable force sensors based on one-dimensional superlattice structures

A proposed force sensor contains a one-dimensional periodic superlattice and piezoceramic wave generator–receiver pair. For force sensing, the strain induced by an applied force in the phononic structure causes stop band frequency variations because the sound velocity varies with the induced strain (stress). When the input wave frequency coincides with the margins of the stop band, it results in noticeable variations in the wave transmission rate with the applied strain. As a result, sensitivity, represented by the transmission rate variation, can be adjusted by introducing distinct acoustic wave frequencies within a phononic structure. A high sensitivity level is suitable for the detection of light forces. Conversely, when dealing with large force measurements, the sensitivity should be reduced to prevent saturation. This study presents theoretical models for analyzing the variation of the transmission rate with frequency and the variation of the stop band with different acoustic parameters. To enhance the signal reaching the receiver, a piezoceramic disk whose axial resonance frequency corresponds to the frequency of the stop band margin is designed. The results indicated that the sensitivity of a prototype of the designed force sensor varied from 15 to 45 mV/N under a compressive force of 50 N.

Ultra-High Frequency Self-Focusing Ultrasonic Sensors With Half-Concave Geometry for Visualization of Mouse Brain Atrophy.

Ultra-high frequency (>100 MHz) acoustic waves feature biocompatibility and high sensitivity and allow biomedical imaging and acoustic tweezers. Primarily, excellent spatial resolution and broad bandwidth at ultra-high frequency is the goal for pathological research and cell selection at the cellular level. Here, we propose an efficient approach to visualize mouse brain atrophy by self-focused ultrasonic sensors at ultra-high frequency with ultra-broad bandwidth. The numerical models of geometry and theoretically predicted acoustic parameters for half-concave piezoelectric elements are calculated by the differential method, which agrees with measured results (lateral resolution: 24 μm, and bandwidth: 115% at -6 dB). Compared with the brain slices of 2-month-old mouse, the atrophy visualization of the 6-month-old mouse brain was realized by C-mode imaging with an acoustic microscopy system, which is a potential prospect for diagnosis and treatment of Alzheimer's disease (AD) combined with neuroscience. Meanwhile, the acoustic properties of the brain slices were quantitatively measured by the acoustic microscopy. These encouraging results demonstrate the promising application for high-resolution imaging in vitro biological tissue with ultra-high frequency self-focusing ultrasonic sensors.

Investigation on submicron particle separation and deflection using tilted-angle standing surface acoustic wave microfluidics

With the development of in vitro diagnostics, extracting submicron scale particles from mixed body fluids samples is crucial. In recent years, microfluidic separation has attracted much attention due to its high efficiency, label-free, and inexpensive nature. Among the microfluidic-based separation, the separation based on ultrasonic standing waves has gradually become a powerful tool. A microfluid environment containing a tilted-angle ultrasonic standing surface acoustic wave (taSSAW) field has been widely adapted and designed to separate submicron particles for biochemical applications. This paper investigated submicron particle defection in microfluidics using taSSAWs analytically. Particles with 0.1–1 μm diameters were analyzed under acoustic pressure, flow rate, tilted angle, and SSAW frequency. According to different acoustic radiation forces acting on the particles, the motion of large-diameter particles was more likely to deflect to the direction of the nodal lines. Decreasing the input flow rate or increasing acoustic pressure and acoustic wave frequency can improve particle deflection. The tilted angle can be optimized by analyzing the simulation results. Based on the simulation analysis, we experimentally showed the separation of polystyrene microspheres (100 nm) from the mixed particles and exosomes (30–150 nm) from human plasma. This research results can provide a certain reference for the practical design of bioparticle separation utilizing acoustofluidic devices.

Low-Loss GHz Frequency Phononic Integrated Circuits in Gallium Nitride for Compact Radio Frequency Acoustic Wave Devices.

Guiding and manipulating GHz frequency acoustic waves in [Formula: see text]-scale waveguides and resonators open up new degrees of freedom to manipulate radio frequency (RF) signals in chip-scale platforms. A critical requirement for enabling high-performance devices is the demonstration of low acoustic dissipation in these highly confined geometries. In this work, we show that gallium nitride (GaN) on silicon carbide (SiC) supports low-loss acoustics by demonstrating acoustic microring resonators with frequency-quality factor ( fQ ) products approaching 1013 Hz at 3.4 GHz. The low dissipation measured exceeds the fQ bound set by the simplified isotropic Akhiezer material damping limit of GaN. We use this low-loss acoustics platform to demonstrate spiral delay lines with on-chip RF delays exceeding [Formula: see text], corresponding to an equivalent electromagnetic delay of ≈ 750 m. Given GaN is a well-established semiconductor with high electron mobility, this work opens up the prospect of engineering traveling wave acoustoelectric interactions in [Formula: see text]-scale waveguide geometries, with associated implications for chip-scale RF signal processing.

Interaction of Staphylococcus aureus and Candida albicans with surface-modified silica studied by ultra-high frequency acoustic wave biosensor.

In this work the bacteria S. aureus and fungi C. albicans were allowed to interact with quartz-based biosensor devices under different flow rates, with and without an anti-fouling coating. These experiments were conducted in order to determine if the level of fouling observed was affected by the flow rate. The biosensor used was an ultra-high frequency acoustic wave device (EMPAS) for investigation of device surface initial interaction of S. aureus or C. albicans under flow of PBS buffer at flow rates between 50 and 200 μL min-1. Surface-bound microbes were also visualized by fluorescence microscopy following these experiments. S. aureus bacteria was able to foul the bare quartz sensors at each flow rate tested, with the greatest degree of fouling observed at a flow rate of 100 μL min-1. C. albicans showed far less fouling of bare devices with the maximum fouling observed at a flow rate of 75 μL min-1. Antifouling MEG-OH coated sensors showed greatly reduced fouling for S. aureus, with between a 90 and 99% reduction in observed frequency change depending on the flow rate used, and between 22 and 90% for C. albicans. Fluorescence images of the microbes following the experiments correlated well with the frequency data, showing a marked decrease in the amount of bacteria seen on MEG-OH-coated surfaces compared to controls.

Interaction of Pseudomonas aeruginosa with surface-modified silica studied by ultra-high frequency acoustic wave biosensor

Aim: This study aimed to examine the amount of surface non-specific adsorption, or fouling, observed by Pseudomonas aeruginosa (P. aeruginosa) on a quartz crystal based acoustic wave biosensor under different flow conditions with and without an anti-fouling layer. Methods: An electromagnetic piezoelectric acoustic sensor (EMPAS) based on electrode free quartz crystals was used to perform the analysis. Phosphate buffered saline (PBS) was flowed over the crystal surface at various flow rates from 50 μL/min to 200 μL/min, with measurements being taken at the 43rd harmonic (~864 MHz). The crystal was either unmodified, or modified with a monoethylene glycol [2-(3-silylpropyloxy)-hydroxy-ethyl (MEG-OH)] anti-fouling layer. Overnight culture of P. aeruginosa PAO1 (PAO1) in lysogeny broth (LB) was injected into the system, and flow maintained for 30 min. Results: The frequency change of the EMPAS crystal after injection of bacteria into the system was found to change based on the flow rate of buffer, suggesting the flow rate has a strong effect on the level of non-specific adsorption. The MEG-OH layer drastically reduced the level of fouling observed under all flow conditions, as well as reduced the amount of variation between experiments. Flow rates of 150 μL/min or higher were found to best reduce the level of fouling observed as well as experimental variation. Conclusions: The MEG-OH anti-fouling layer is important for accurate and reproducible biosensing measurements due to the reduced fouling and variation during experiments. Additionally, a flow rate of 150 μL/min may prove better for measurement compared to the current standard of 50 μL/min for this type of instrument.

Experimental analysis of heat transfer characteristics using ultrasonic acoustic waves

In this experimental work, heat transfer intensification using ultrasonic waves was investigated. A heat source, consisting in a parallelepiped aluminum block in which two electrical heating cartridges of 160 W each were mounted to heat four liters of distilled water contained in a tank made of Plexiglas. To demonstrate the effectiveness of heat transfer enhancement with the use of ultrasounds, three different configurations were analyzed. In the first one, considered as a reference case, the heat transfer was studied without ultrasound field. In the second configuration, ultrasonic acoustic waves were generated using one transducer vibrating at a fixed frequency of 40 kHz with a total power of 60 W. In the last configuration, ultrasounds were generated with two similar transducers mounted on two opposite walls of the water tank while maintaining the same power and frequency. The effect of the distance separating the heat source to the trans-ducers on the convective heat transfer coefficients and the average temperature of the water in the tank were analyzed in detail. The results revealed that the natural convection heat transfer in the water tank was intensified by means of low frequency acoustic waves. Indeed, it was shown, particularly, that more the distance between the transducer and the heater is low more the heat transfer improvement is better. The heat transfer enhancement factor was estimated to 2.5 on the surface facing the transducer while it was only about 1.2 on the opposite surface in C2 configura-tion. In C3 configuration, the heat transfer enhancement factor is nearly the same with, however, more homogenous water temperature. The acoustic cavitation and streaming were identified as the main phenomena leading to these results. This study successfully demonstrated the feasibility of heat transfer intensification using low frequency ultrasonic waves.

Damped quantum drift Zakharov-Kuznetsov equation for a dissipative inhomogeneous partially degenerate plasma with quantizing magnetic field

Damped quantum drift Zakharov-Kuznetsov (DQDZK) equation is investigated in two dimensions for a spatially inhomogeneous and dissipative plasma with adiabatic electron trapping in the presence of quantizing magnetic field and partial degeneracy. Linear and nonlinear analysis is presented in detail. For the 2D case, it is observed that the angular frequency of linear drift ion acoustic wave (DIAW) exhibits a cut-off point that gets modified by Landau quantization and partial degeneracy of the trapped electrons. It is observed that the inclusion of ion-neutral collisions leads to the formation of DQDZK equation for the system under consideration. The DQDZK is solved analytically using the hyperbolic tangent method and a decaying solitary wave solution is obtained. It is shown that the effects of quantizing magnetic field, partial degeneracy, and obliqueness significantly modify the properties of the nonlinear drift ion acoustic structures. The results presented here can be gainfully employed to understand the linear and nonlinear wave propagation in dense degenerate plasmas present in astrophysical compact objects like white dwarfs and neutron stars.

Acoustic standing wave with a frequency sweeping in a microfluidic system of parallel channels

In acoustofluidics, particles driven by fluid flows in microchannels are subject to acoustic waves, which are transmitted through the channel walls. Increasing the flow rate, one of the major challenges in microfluidic operation, can be achieved by parallelization of channels. In the present paper, inducing acoustic waves in devices with 4 and 16 parallel channels in silicon-based chip is studied. The resonance quality was evaluated by acoustic focusing of particles in the channels. First, the quality of resonance was measured in every channel separately as a function of the wave frequency. Second, a methodology with a sweeping of the frequency with time was explored to compensate for the variation of the optimal frequency between the channels.As a result, for a chip with a single channel, the sweeping is less efficient because of the lower energy transfer due to a non-optimal acoustic wave frequency. However, this developed method allowed simultaneous resonance in all the channels, which is not possible with application of a single frequency.

Sensitivity of an optical feedback interferometer for acoustic waves measurements.

This work presents a sensitivity study on the use of an optical feedback interferometer to measure acoustic pressure from plane waves. The sensitivity is established by linearising the interferometer's governing equations. It is shown to be independent of the acoustic wave frequency but dependent on configuration parameters such as the optical feedback parameter or the length of the laser through which the acoustic wave passes. Experimental validation is carried out using three acoustic waveguides in the 0.5-18 kHz range. The sensitivity obtained enables broadband acoustic pressure measure with a low mean relative error in comparison with a reference condenser microphone.

Indirect nanoscale characterization of polymer photoresist wetting using ultra-high frequency acoustic waves

The wetting of surfaces with patterns in the order of a hundred nanometers is often a complex phenomenon to analyze and control. In the semiconductor industry, whether it is during the surface cleaning steps or the deposition of the protective mask (photosensitive liquid resin that is then cross-linked), the conformity of the deposit of the liquid layer on the patterned surface must be perfect or else the functionality of the targeted electronic component will be compromised. Thus, understanding the surface wetting of these liquids allows the implementation of optimized processes. In this paper, we present a method of indirect wetting characterization of a photoresist based on ultra-high frequency (# GHz) acoustic waves. This resin is a commercial product called GKR 4602 (belonging to the KrF series of positive photoresists), which is coated in two different ways: either directly onto the surface of a patterned silicon wafer, or after application of a solvent, Propylene Glycol Ethyl Ether (PGEE), which then acts as a pre-wetting layer. The patterned wafer, playing the role of electrical insulation (Deep Trench Isolation, DTI) are 200 nm wide, deep trenches with a high aspect ratio (> 50). The originality of this paper lies in the validation of the acoustic characterization by direct observation of the wetting of the cross-linked resin. To do so, we used a FIB (Focused Ion Beam) microscope which allowed us to make cuts and capture localized images of the wetting state of the photoresist. Moreover, all the results obtained (resins and patterned silicon surfaces) are directly from the microelectronics industry (STMicroelectronics), showing that our method is fully compatible with an industrial approach.

Signature of thunderstorm induced acoustic and gravity waves at low latitude Indian sector

This study reports thunderstorm-generated acoustic and gravity waves from a tropical location using newly launched Indian navigation system NavIC for the first time. The detection of acoustic wave components in travelling ionospheric disturbance (TID) measurement is very significant. In compared to acoustic wave gravity wave signature is more ubiquitous because gravity wave propagates in thermospheric altitude by dissipative filtering process. The turbulent nature in plasma characteristics due to strong vertical drift and plasma motion in lower latitude region generate strong scintillation effect and plasma bubble. Large temperature gradient at thermospheric altitude also provides a strong attenuation effect in this region for comparatively high frequency acoustic wave. We have found the TID signatures on TEC variation for acoustic wave up to 0.4 TECU for both the days whereas gravity wave induced signatures went up to 0.8 TECU. Measurements using GPS signal validate signatures obtained from the NavIC signal. The study shows the potential of application of NavIC system for middle atmosphere as well as thermospheric study and understanding of coupling process between various atmospheric layers in tropical region which is not well known so far.

Condensation Heat Transfer and Pressure Drop of Acoustically Actuated Horizontal Two-Phase Flow

An acoustic actuation technique to enhance condensation inside horizontal tubes is developed and experimentally demonstrated. Heat exchanger headers are used as Helmholtz resonators, allowing low-frequency (∼10 Hz) acoustic waves to propagate and be reflected within the condenser, improving mixing saturated vapor and condensed liquid, thereby enhancing heat transfer. Heat transfer coefficients and pressure drops are measured to evaluate the heat transfer enhancement and pressure drop penalty as a function of vapor quality, mass flux, temperature difference, and acoustic wave amplitude and frequency. Experiments are conducted using a tube-in-tube heat exchanger with an inner diameter of 14.45 mm that partially condenses refrigerant R134a at 950 kPa across vapor qualities ranging from 5% to 80% as mass fluxes of 120 and 180 kg m−2 s−1 and temperature differences of 6 and 12 K. The actuation amplitude and frequency are varied from 0.5 to 6 mm and 2 – 20 Hz, respectively to characterize the acoustic response. Heat transfer enhancement mechanisms are hypothesized and evaluated based on the experimental results, concluding that changes in two-phase flow patterns and increased convective effects lead to significant enhancement at low qualities but negligible enhancement at high qualities when the flow is annular. Existing correlations and modifications to existing models are proposed to explain the observed enhancement, and a simple correlation based on a heat-and-momentum analogy is proposed, which predicts both baseline and enhanced heat transfer data within 2.7%.