Acoustic Field Intensity Research Articles

Deep-Learning-Based Source Localization Using a Local 3-D Acoustic Intensity Field in a Sound-Speed Mismatched Deep-Ocean Environment

Deep-Learning-Based Source Localization Using a Local 3-D Acoustic Intensity Field in a Sound-Speed Mismatched Deep-Ocean Environment

Green efficient preparation and on-line monitoring: Hybrid effect of okra pectin and controlled-temperature ultrasound on physicochemical properties of low-fat yogurt

Pectin replaces fat as a stabilizer in making green low-fat yogurt. Controlled-temperature ultrasonic-assisted fermentation (CTUAF) was used, and its acoustic field was monitored in time-frequency domains during the fermentation. Meanwhile, the effect of the addition of okra pectin (OP) on the acoustic field intensity in the yogurt was discussed. Furthermore, the synergistic effect of ultrasound and OP on the physicochemical and structural properties of yogurt was studied, including post processing operations and storage of yogurt. Results showed that adding OP increased the intensity of acoustic field and improved the efficiency of yogurt fermentation. 0.1% OP, ultrasound and hybrid of both shortened the fermentation time of yogurt by 0.75 h, 0.5 h and 1.0 h, respectively. Ultrasound and OP reduced syneresis and optimized hardness, rheological properties and processing quality of yogurt. The cross-linking of OP with casein increased and filled casein cavities, and ultrasound enhanced this interaction. The hybrid of OP and CTUAF also improved the survival rate of probiotics.

Multi-plane acoustic hologram generation with a physics-enhanced neural network for micro-particle manipulation

A physics-enhanced multi-plane acoustic hologram deep neural network (PhysenNet_MPAH) approach is proposed for generating multi-plane acoustic hologram. By combining a convolutional neural network with a physical model, the PhysenNet_MPAH approach can generate high-quality acoustic holograms for holographic rendering of targeted acoustic intensity fields at multiple planes. This approach is capable of reconstructing both strong and weak-targeted multi-plane fields, with superior quality compared to traditional iterative angular spectrum approach. The reconstructed multi-plane acoustic fields are also demonstrated to be useful for three-dimensional particles manipulation, indicating potential applications in dynamic particles manipulation and volumetric display.

The Influence of Bottom Sediment on the Propagation of Caustic Beams in Oceanic Waveguides

Numerical modeling with the use of mode theory was used to investigate the regularities of the spatial (depth and horizontal distance) distribution of the acoustic field intensity formed by multiple interaction of a caustic beam with a layered bottom in a shallow oceanic waveguide with an underwater sound channel open to the bottom. It has been established that at the values of the sound velocity at the upper boundary in the sedimentary layer, less than the sound velocity at the bottom in the water layer, the formation of a multi-beam structure of the acoustic field is possible. It was found that, starting from certain distances, newly formed beams can play the main role in the spatial distribution of the acoustic field intensity.

Multi-frequency acoustic hologram generation with a physics-enhanced deep neural network

Here, a physics-enhanced multi-frequency acoustic hologram deep neural network (PhysNet_MFAH) method is proposed for designing multi-frequency acoustic holograms, which is built by incorporating multiple physical models that represent the physical processes of acoustic waves propagation for a set of design frequencies into a deep neural network. It is demonstrated that one needs only to feed a set of frequency-specific target patterns into the network, the proposed PhysNet_MFAH method can automatically, accurately, and rapidly generate a high-quality multi-frequency acoustic hologram for holographic rendering of different target acoustic fields in the same or distinct regions of the target plane when driven at different frequencies. Remarkably, it is also demonstrated that the proposed PhysNet_MFAH method can achieve a higher quality of the reconstructed acoustic intensity fields than the existing optimization methods IASA and DS for designing multi-frequency acoustic holograms at a relatively fast-computational speed. Furthermore, the performance dependencies of the proposed PhysNet_MFAH method on different design parameters are established, which provide insight into the performance of the reconstructed acoustic intensity fields when subject to different design conditions of the proposed PhysNet_MFAH method. We believe that the proposed PhysNet_MFAH method can facilitate many potential applications of acoustic holograms, ranging from dynamic particle manipulation to volumetric display.

Acoustophoresis separation of particles based on motion modes via tilted-angle standing surface acoustic wave driven by a unidirectional transducer

Acoustophoresis separation technique has attracted great attention due to its superior properties, such as biocompatibility, non-contact, label-free and high-efficiency. In this paper, separation of particles based on motion modes via tilt angle standing surface acoustic wave (TaSSAW) driven by a unidirectional transducer is developed theoretically. It is verified that the designed electrode width controlled unidirectional transducers are effective to improve the intensity of the acoustic field and the acoustic radiation force of the particles in the channel. The results show that when the density and compressibility of the particles are close to those of the fluid and the particle shape is close to spherical, the influences of fluid viscosity and particle shape on the acoustic radiation force are negligible. It is found that in the TaSSAW system the motion modes of the particles are divided into locked mode and drift mode, and they depend on the fluid velocity, acoustic field intensity and tilt angle. polystyrene (PS) particles with radii of 4 and 5 µm are separated based on the differences of motion modes. For further smaller size difference (4.5 and 5 µm) particles, the separation is also realized successfully by making particles move in the same drift mode.

Nanostructured Sonophotocatalysts for spatially controlled inertial cavitation towards energy‐efficient sonochemistry

AbstractCatalytic nanomaterials have been demonstrated to enhance sonochemical processing through interactions with inertial cavitation events. Typically, sonochemistry generates inertial cavitation events directly from the solvent, which results in spatially uncontrolled cavitation events with limited interaction with the catalytic active site. These high intensity acoustic fields also result in thermal effects and side reactions, which may further influence chemical yields and selectivity. Herein, we report on ultrasound‐responsive structured AuPd/TiO2 open nanoshells (TONs) to surface‐stabilize gas bubbles for promoting cavitation events in the vicinity of catalytic active site. These exogenous bubbles trapped on catalytic active sites readily cavitate to produce free radicals for chemical reactions. Our findings indicate a positive trend between cavitation and benzaldehyde production in the presence of our AuPd/TONs. In contrast, nanostructures without gas‐stabilization demonstrate reduced sonochemical conversion, suggesting the catalytic potential of nanostructuring photocatalytic materials to function as both cavitation agents and photo‐oxidative catalysts, or photocatalytic nanostructure (PCN).

Contactless Ultrasonic Cavitation for the Prevention of Shunt Obstruction in Hydrocephalus: A Proof-of-Concept Study.

Obstructive failure of implanted shunts is the most common complication in the treatment of hydrocephalus. Biological material and debris accumulate in the inner walls of the valve and catheters block the normal flow of the drained cerebrospinal fluid causing severe symptoms with high morbidity and mortality. Unfortunately, at present, there is no effective preventive protocol or cleaning procedure available. To assess whether externally applied, focused ultrasound beams can be used to resuspend deposits accumulated in brain shunts safely. A computational model of an implanted brain shunt was implemented to test the initial design parameters of a system comprising several ultrasound transducers. Under laboratory conditions, configurations with 3 and 4 transducers were arranged in a triangle and square pattern with their radiation axis directed towards a target model of the device, 2 catheters and a brain shunt filled with water and deposited graphite powder. The ultrasound beams were then concentrated on the device across a head model. The computational model revealed that by using only 3 transducers, the acoustic field intensity on the valve was approximately twice that on the brain surface suggesting that acoustic cavitation could be selectively achieved. Resuspension of graphite deposits inside the catheters and the valve were then physically demonstrated and video-recorded with no temperature increase. The technology presented here has the potential to be used routinely as a noninvasive, preventive cleaning procedure to reduce the likelihood of obstruction-related events in patients with hydrocephalus treated with an implanted shunt.

Maximizing the Number of Spatial Nulls with Minimum Sensors

In this paper, we attempt to unify two array processing frameworks viz, Acoustic Vector Sensor (AVS) and two level nested array to enhance the Degrees of Freedom (DoF) significantly beyond the limit that is attained by a Uniform Linear Hydrophone Array (ULA) with specified number of sensors. The major focus is to design a line array architecture which provides high resolution unambiguous bearing estimation with increased number of spatial nulls to mitigate the multiple interferences in a deep ocean scenario. AVS can provide more information about the propagating acoustic field intensity vector by simultaneously measuring the acoustic pressure along with tri-axial particle velocity components. In this work, we have developed Nested AVS array (NAVS) ocean data model to demonstrate the performance enhancement. Conventional and MVDR spatial filters are used as the response function to evaluate the performance of the proposed architecture. Simulation results show significant improvement in performance viz, increase of DoF, and localization of more number of acoustic sources and high resolution bearing estimation with reduced side lobe level.

Feasibility investigation of rail monitoring by wheel-mounted acoustic emission technology using two-dimensional analytical contact acoustic nonlinearity model

In an attempt to analyze the feasibility of a rail monitoring scheme with a wheel-mounted acoustic emission measurement method, a two-dimensional analytical spring model was proposed to interpret the interactions between acoustic waves and stationary wheel–rail contact interfaces. The spring model represents the coupling strength of the interfaces with their stiffness. It accommodates the environmental information of contact stiffness and the acoustic source information, such as the feature frequency and the incident angle in the analysis of interface transmissibility. The fractal dimension of the interface is introduced into the spring model to interpret the effect of the axle load on the interface stiffness and the variation in transmissibility. Discrete Rayleigh integration is further combined to obtain the directivity of the interface and estimate the acoustic field intensity in the entire wheel. A wheel–rail contact rig was designed to simulate the actual contact conditions in a railway. Experimental data acquired from this test rig were utilized to validate the model, with regard to the interfacial stiffness in normal incidence and amplitudes of the transmitted waves in oblique incidence. After verifying the reliability of the model, the acoustic field intensity in the wheel was visualized under the assumed environmental conditions. Finally, a discussion is presented to determine a proper angular separation for the wheel-mounted sensor system, and substantiate the feasibility of the system.

Optimized integrated design of a high-frequency medical ultrasound transducer with genetic algorithm

Designing efficient acoustic stack and elements for high-frequency (HF) medical ultrasound (US) transducers involves various interrelated parameters. So far, optimizing spatial resolution and acoustic field intensity simultaneously has been a daunting task in the area of HF medical US imaging. Here, we introduce optimized design for a 50-MHz US probe for skin tissue imaging. We have developed an efficient design and simulation approach using Krimholtz, Leedom and Matthaei (KLM) equivalent circuit model and spatial impulse response method by means of Field II software. These KLM model and Field II software are integrated, and a GA algorithm is used to optimize the design of the US transducer to obtain the best imaging performance. As a result, a 50-MHz single element probe is effectively optimized with 5 mm acoustic focal length, 72 upmu {text{m}} lateral, and 42 upmu {text{m}} axial imaging resolution, with an enhancement in imaging resolution over the conventionally designed and simulated probe by 10%. This work has the potential to benefit many applications that require a fast, high-resolution and strong US focus in skin imaging.

Multiphysics Modelling of Ultrasonic Melt Treatment in the Hot-Top and Launder during Direct-Chill Casting: Path to Indirect Microstructure Simulation

This study concerns the numerical simulation of two competing ultrasonic treatment (UST) strategies for microstructure refinement in the direct-chill (DC) casting of aluminium alloys. In the first, more conventional, case, the sonotrode vibrating at 17.3 kHz is immersed in the hop-top to treat the sump melt pool, in the second case, the sonotrode is inserted between baffles in the launder. It is known that microstructure refinement depends on the intensity of acoustic cavitation and the residence time of the treated fluid in the cavitation zone. The geometry, acoustic field intensity, induced flow velocities, and local temperature are factors which affect this treatment. The mathematical model developed in this work couples flow velocity, acoustics modified by cavitation, heat transfer, and solidification at the macroscale, with Lagrangian refiner particles, used to determine: (a) their residence time in the active zones, and (b) their eventual distribution in the sump as a function of the velocity field. This is the first attempt at using particle models as an efficient, though indirect, alternative to microstructure simulation, and the results indicate that UST in the launder, assisted with baffle separators, yields a more uniform distribution of refining particles, avoiding the strong acoustic streaming jet that, otherwise, accompanies hot-top treatment, and may lead to the strong segregation of refining particles. Experiments conducted in parallel to the numerical studies in this work appeared to support the results obtained in the simulation.

Three-dimensional acoustic energy flow from rotating sound sources

A detailed study of the three-dimensional sound fields around a monopole point source in subsonic and supersonic rotation is investigated. We calculate the sound pressure, the acoustic velocity, as well as the instantaneous and time-averaged acoustic intensity fields with the advanced time approach. The advanced time approach is applied for sound sources at subsonic and supersonic rotation and yield comparable results as those obtained from the spherical harmonic series expansion method or the solution of the retarded time equation. Further, the direction of the time-averaged acoustic energy flow is derived from the acoustic intensity vectors. It is shown, that the direction of the energy flow path differs from the radial direction and depends on the rotational direction and rotational velocity. Those findings are useful, for example, to improve the acoustic absorption performance of sound absorbers and acoustic liners around turbomachines.

Laser adaptive holographic hydroacoustic intensimeter

A new type of a vector hydrophone, a laser adaptive hydroacoustic intensimeter, is investigated. Two identical, spatially separated coil-type sensors are used as a primary receiver of the acoustic signal. The signals received at the sensor output are phase demodulated in a two-channel adaptive holographic interferometer based on two dynamic holograms multiplexed in a CdTe photorefractive crystal. Using a laser intensimeter, the acoustic field formed in a limited volume is studied. The performance characteristics of the intensimeter are determined experimentally; its threshold sensitivity, according to the acoustic field intensity, constitutes 0.1 × 10−13 W m−2.

LIPUS far-field exposimetry system for uniform stimulation of tissues in-vitro: development and validation with bovine intervertebral disc cells

Therapeutic Low-intensity Pulsed Ultrasound (LIPUS) has been applied clinically for bone fracture healing and has been shown to stimulate extracellular matrix (ECM) metabolism in numerous soft tissues including intervertebral disc (IVD). In-vitro LIPUS testing systems have been developed and typically include polystyrene cell culture plates (CCP) placed directly on top of the ultrasound transducer in the acoustic near-field (NF). This configuration introduces several undesirable acoustic artifacts, making the establishment of dose-response relationships difficult, and is not relevant for targeting deep tissues such as the IVD, which may require far-field (FF) exposure from low frequency sources. The objective of this study was to design and validate an in-vitro LIPUS system for stimulating ECM synthesis in IVD-cells while mimicking attributes of a deep delivery system by delivering uniform, FF acoustic energy while minimizing reflections and standing waves within target wells, and unwanted temperature elevation within target samples. Acoustic field simulations and hydrophone measurements demonstrated that by directing LIPUS energy at 0.5, 1.0, or 1.5 MHz operating frequency, with an acoustic standoff in the FF (125–350 mm), at 6-well CCP targets including an alginate ring spacer, uniform intensity distributions can be delivered. A custom FF LIPUS system was fabricated and demonstrated reduced acoustic intensity field heterogeneity within CCP-wells by up to 93% compared to common NF configurations. When bovine IVD cells were exposed to LIPUS (1.5 MHz, 200 μs pulse, 1 kHz pulse frequency, and ISPTA = 120 mW cm−2) using the FF system, sample heating was minimal (+0.81 °C) and collagen content was increased by 2.6-fold compared to the control and was equivalent to BMP-7 growth factor treatment. The results of this study demonstrate that FF LIPUS exposure increases collagen content in IVD cells and suggest that LIPUS is a potential noninvasive therapeutic for stimulating repair of tissues deep within the body such as the IVD.

Evolution of Flow and Streaming in Exponential Variable Cross-Section Resonators

A gas-kinetic scheme (GKS) based on an unstructured grid is applied to simulate the evolution of the fluid motions in exponential variable cross-section resonators. The effects of the acoustic field intensity on the oscillatory pressure, velocity, temperature, and flow streaming structure were investigated numerically, and the model was validated. The results demonstrate that the geometry and driving strength are the main factors affecting the final performance of the system. For the quasi-linear and moderate non-linear cases in optimum exponential tube, the periodic generation, evolution, and shedding of vortices in flow fields are associated with the storage and release of energy, which is the transmission mode of the third type of direct current (DC) flow, and its driving mechanism is attributed to the asymmetrical pressure and temperature. Meanwhile, some new physical characteristics were also discovered for the highly non-linear case, e.g., the disorder and unsteadiness of the flow direction accomplished with turbulent flow streaming structures. The secondary flow is manifested as multiscale, irregular and unsteady vortices throughout the tube. The smallest increment of pressure and velocity amplitude occurs concurrently with the biggest increment of temperature amplitude. These evidences suggest that there is an optimal driving strength, even for a good configuration tube, with which the maximum efficiency can be obtained.

Caustic and Weakly Diverging Beams in Horizontally Inhomogeneous Oceanic Waveguides

Using approximate analytical calculations based on the WKB and adiabatic approximations for the mode representation of the field, as well as numerical simulation based on the theory of adiabatic modes, geometric acoustic approximation, and the parabolic equation method, the patterns of the formation and propagation of caustic and weakly diverging acoustic beams in a horizontally inhomogeneous refractive oceanic waveguide are studied. The horizontal distance regions are determined at which the dependences of the acoustic field intensity on the horizontal distance typical of caustic and weakly diverging beams are retained. The study considers the processes involved in reformation of caustic and weakly diverging beams in an oceanic waveguide with increasing water layer depth and constant sound speed profile, which near the source characterized an underwater sound channel open toward the bottom. The conditions are formulated for an effectively matched transition of shallow-water waveguide modes refracted in the thermocline and interacting with the bottom to purely refracted modes of the underwater sound channel in a relatively deep water part of the oceanic waveguide.

Force and Sound Pressure Sensors Used for Modeling the Impact of the Firearm with a Suppressor

In this paper, a mathematical model for projectiles shooting in any direction based on sensors distributed stereoscopically is put forward. It is based on the characteristics of a shock wave around a supersonic projectile and acoustical localization. Wave equations for an acoustic monopole point source of a directed effect used for physical interpretation of pressure as an acoustic phenomenon. Simulation and measurements of novel versatile mechanical and acoustical damping system (silencer), which has both a muzzle break and silencer properties studied in this paper. The use of the proposed damping system can have great influence on the acoustic pressure field intensity from the shooter. A silencer regarded as an acoustic transducer and multi-holes waveguide with a chamber. Wave equations for an acoustic monopole point source of a directed effect used for the physical interpretation of pressure as an acoustic phenomenon. The numerical simulation results of the silencer with different configurations presented allow trends to be established. A measurement chain was used to compare the simulation results with the experimental ones. The modeling and experimental results showed an increase in silencer chamber volume results in a reduction of recorded pressure within the silencer chamber.

Calcium-looping for thermochemical energy storage in concentrating solar power applications: Evaluation of the effect of acoustic perturbation on the fluidized bed carbonation

In the framework of thermochemical energy storage (TCES) in concentrating solar power (CSP) plants, the calcium-looping (CaL) process, carried out in fluidized bed reactors, is receiving increasing research interest due to the high energy density and the extremely low price, nontoxicity, and wide availability of natural CaO precursors. One of the main open challenges in CaL is represented by finding solutions to the progressive decline in the CaO carbonation conversion with the number of cycles, which is due to the sorbent deactivation caused by sintering and pore-plugging. In this framework, the reduction of the CaO particles size has been reported to improve the carbonation conversion and, therefore, the achievable energy density, by maximizing the availability of the sorbent surface exposed to the gaseous phase and hindering the natural loss of CaO mutlicyclic activity. However, the use of fine particles in fluidized bed reactors is challenging due to agglomeration, channeling and plugging phenomena. In this work, the possibility to use a fine natural limestone (<50 μm) for CaL at TCES-CSP conditions in a fluidized bed reactor has been investigated for the first time. In particular, sound-assisted fluidization has been proposed as technique to allow the use of such fine particles in fluidized bed reactors, thus overcoming the strict limitation posed by particle size applicable in ordinary fluidized bed reactors. Ordinary and sound-assisted cyclic CaL tests at CSP-TCES operating conditions have been performed in a lab-scale fluidized bed reactor in order to study the influence of the application of high intensity acoustic fields on the carbonation performances. The effect of sound parameters (SPL and frequency) has also been highlighted.

Acoustic deformation for the extraction of mechanical properties of lipid vesicle populations.

We use an ultrasonic standing wave to simultaneously trap and deform thousands of soft lipid vesicles immersed in a liquid solution. In our device, acoustic radiation stresses comparable in magnitude to those generated in optical stretching devices are achieved over a spatial extent of more than ten acoustic wavelengths. We solve the acoustic scattering problem in the long-wavelength limit to obtain the radiation stress. The result is then combined with thin-shell elasticity theory to form expressions that relate the deformed geometry to the applied acoustic field intensity. Using observation of the deformed geometry and this model, we rapidly extract mechanical properties, such as the membrane Young's modulus, from populations of lipid vesicles.