Changes In Acoustic Impedance Research Articles

Underwater Acoustic Propagation using Monterey-Miami Parabolic Equation in Shallow Water Kayeli Bay Buru Distric

Indonesia's geographical position is an advantage compared to other countries, both in terms of geoeconomics, geopolitics and geostrategy. For this reason, it is necessary to develop and use acoustic methods to describe underwater features, carry out underwater communications or to measure oceanographic variables at sea. This research was intended to provide an analytical and visual graphical description with the aim that it can be used for various purposes both in the research, military and other marine fields, as well as to analyze the influence of sediment and different frequencies on acoustic propagation patterns in shallow waters of Kayeli Bay. This research was conducted using CTD data from Kayeli Bay, which is a body of water in Buru Regency, Maluku Province and is located between 3° 15' 55'' – 3° 22' 50" S and 127° 01'35" – 127° 01' 35 "E, using the Monterey-Miami parabolic equation method using 4 types of sediment and 3 different frequencies as model input. From the results of this research it can be concluded that the propagation of sound waves in shallow seas is greatly influenced by the type of sediment and frequenty used. Changes in acoustic impedance at the bottom of the water and within the water column can significantly influence the behavior of acoustic waves in shallow water environments, and accurate acoustic impedance data are critical for effective ray tracing modelling.

Оptimization of the parameers of the placement of elements of the acoustic system for orientation of rescuer's equipment

Experimentally determined correction values of the distance to the obstacle depending on the acoustic impedance of the environment for the acoustic device of the rescuer's equipment. The measurement results were obtained using the developed experimental setup, which took into account, in real time, changes in acoustic impedance and temperature of the environment using a two-channel temperature meter and an optical penetration sensor of the environment. The temperature of the environment (in the confined space) varied from 20 C to 60 C, and the optical penetration index from 0 to 100 %, where 100 % corresponds to complete optical opacity of the environment. Dependencies of the propagation of acoustic waves upon changing the optical permeability of the medium and temperature were obtained. The correction value for the distance to the obstacle calculated by the acoustic device at a distance of 1000 mm was (+0,013 m). The relative error during the measurements did not exceed 2 %. It was found that when the wave impedance increases, the indicators of the distance to the obstacle decrease, so the corrective dependence has a positive value. The obtained results make it possible to increase the reliability of the readings of the acoustic device as an additional equipment of the rescuer. The data obtained as a result of the experiment make it possible to display the shape of the obstacle in more detail. Approximating polynomials of the reflection coefficient of acoustic waves depending on the volume content of inclusions at angles of incidence from 0 °С to 30 °С have been determined. The use of the obtained polynomials allows to increase the speed of the program code of the control microcontroller of the acoustic device. The obtained dependencies are taken into account in the calculation algorithm of the program code of the microcontroller of the acoustic device for determining the shape and distance to the obstacle, which makes it possible to increase the efficiency of the rescuer's orientation in conditions of unsatisfactory visual control during emergency rescue operations.

The Influence of the Shape of Acoustic Impedance Change on the Propagation of a Mechanical Wave in Multilayer Phononic Structures

The Influence of the Shape of Acoustic Impedance Change on the Propagation of a Mechanical Wave in Multilayer Phononic Structures

Experimental validation of a multi-material acoustic black hole

Geometric acoustic black holes (ABHs) have already been proven as an effective passive vibration control measure in plates and beams. However, the thin geometries inherent to the design raise concerns about the structure’s resistance to damage through fatigue. Multi-material ABHs (MM-ABHs) have been proposed as an alternative solution where by the material properties vary along the direction of wave propagation instead of the geometry. This, in theory, produces a change in acoustic impedance without the issues of fatigue seen in the geometric ABHs. Previous work has been performed on the design and modeling of polymer multi-material ABHs. This work discusses practices for experimental measurement and validation of multi-material ABHs produced through additive manufacturing.

Fully optic characterization of acoustic impedance implementable in conventional optical microscope

The intrinsic acoustic impedance (Z) changes with inflammation and canceration. This paper proposes an optically Z measurement method using a common optical microscope for simultaneous measurement of optical-acoustical observation. Photoacoustic (PA) waves were generated by the PA effect of the pulsed laser (a 527 nm nanosecond laser light) at the black ink and resin pasted area on the outside of the bottom of the petri dish (surface A). The generated PA waves propagated to the inner boundary of the petri dish and reflected, with a reflection coefficient of R. The reflected waves propagated to surface A and vibrated it. The surface vibration was measured with a self-built Sagnac interferometer using a contentious light laser and a 10x objective lens. Measurements were made air-filled and water-filled petri dishes. The observed times of echo signal corresponded to the sound speed of longitudinal and transverse propagation. The reflected wave amplitude of air was larger than in a water-filled petri dish. They related that R water and R air are 0.24 and 1.00, respectively. There corresponds to the Z ratio of the polystyrene petri dish and the water or air inside. Thus, this result showed that sample Z was measured optically.

High-performance phononic crystal sensing structure for acetone solution concentration sensing

A two-dimensional phononic crystal sensor model with high-quality factor and excellent sensitivity for sensing acetone solutions and operating at 25–45 kHz is proposed. The model for filling solution cavities is based on reference designs of quasi-crystal and gradient cavity structures. The transmission spectrum of sensor is simulated by the finite element method. High-quality factor of 45,793.06 and sensitivity of 80,166.67 Hz are obtained for the acetone concentration with 1–9.1%, and quality factor of 61,438.09 and sensitivity of 24,400.00 Hz are obtained for the acetone concentration range of 10–100%, which indicated the sensor could still achieve high sensitivity and quality factor at operating frequencies from 25 to 45 kHz. To verify the application of the sensor to sensing other solutions, the sensitivity for sound velocity and density is calculated as 24.61 m-1 and 0.7764 m3/(kg × s), respectively. It indicates the sensor is sensitive to acoustic impedance changes of the solution and equally suitable for sensing other solutions. The simulation results reveal the phononic crystal sensor possessed high-performance in composition capture in pharmaceutical production and petrochemical industry, which can provide theoretical reference for the design of new biochemical sensors for reliable detection of solution concentration.

Mass-balance threshold matching of geoelectric and seismic data: a case study from Ketzin

Abstract Seismic and geoelectric methods are used as complementary tools for the identification of fluid/gas effects in underground storage and production scenarios. Both methods present a different resolution. Seismic data tend to be acquired by much more dense geometrical layouts, and geoelectric acquisition as a potential field method shows information integrated over spatial distances. We present results matching seismic and electrical resistivity tomography (ERT) results from two repeat surveys performed during CO 2 storage operations at the Ketzin pilot site in Germany. The approach is based on data acquired in 2009 and 2012 at different stages of total injected CO 2 volume. Masses are obtained from the averaged change in acoustic impedance and are compared to masses inferred from inverted electrical resistivities. Archie's equation is used to obtain saturations from the ERT models. The sensitivity of the background resistivity, R 0 , as a relevant parameter in determining the mass of injected CO 2 is analysed. A specific threshold analysis based on seismic thickness by bin has been applied to investigate the matching of seismically and ERT obtained masses. Both mass estimates match comparatively well, but show inherent sensitive parameters and their corresponding impact as temporal and spatial uncertainties that may cause mass differences for the areas of investigation.

Impact of model and data resolutions in 4D seismic data assimilation applied to an offshore reservoir in Brazil

Data assimilation is the process where reservoir models are calibrated using dynamic data. The goal is to reduce uncertainties related to reservoir properties for more assertive model-based forecasts and decisions. The use of 4D seismic data as input to this process allows model properties to be updated so that dynamic changes are better represented in the entirety of the reservoir. However, in many cases, the higher the number of grid blocks, the more time consuming are the models' simulation. Thus, the balance between the fidelity of models and simulation runtime in a project is crucial in the planning of activities. The objective of this work is to discuss the impact of using grids with different resolutions and explore options to incorporate 4D seismic maps in data assimilation and production forecast. Through a real field application, we evaluate the use of two grids with different vertical and lateral resolutions, using the Ensemble Smoother with Multiple Data Assimilation (ES-MDA) method. The available high-quality seismic data, applied to a Bayesian inversion, generated 4D impedances that helped identify important dynamic changes that happen at intermediate layers of a thin reservoir (averaged 25 m thickness), located in Brazil. Thus, we also evaluate two approaches for models updating with 4D seismic data: treating the entire reservoir as a single interval, and considering a greater vertical resolution by adding information at intermediate layers. Overall, well production misfits between posterior models and observed data were considerably reduced when assimilating seismic and production data simultaneously, presenting even smaller errors than production data only cases. This happened for both grids. By adding further 4D information at intermediate layers with the use of two maps, we observed (in both grids) that posterior models could predict important reservoir behaviors, such as the gas trapping in the deeper interval. The coarser grid presented lower well production data misfits compared to the refined grid, but showed to be insensitive to the use of different seismic data in data assimilation, resulting in alike models. Furthermore, the posterior models for the coarse grid presented similar behaviors when performing production forecast, which indicates that the uncertainties may be underestimated in these cases. The refined grid presented slightly greater production misfits but was more sensitive to the different 4D seismic inputs. In this grid, an increased ensemble variance was observed between the posterior models, which is also observed in the long-term forecasts. Also, the most refined grid yielded estimates of acoustic impedance changes visually closer to the observed data than those obtained from the coarser grid. As a real case application, the definition of the best procedure is not straightforward. Results suggest that both grids can be used depending on the project's objective. The coarser grid is a good option for short-term studies, since it is able to properly represent the near future with much cheaper models. The refined grid may be suitable for long-term decisions, because it better represents models' uncertainties and provides safer risk analyses.

Evaluation of elastic change during the mitotic phase of murine breast cancer cells using scanning acoustic microscopy

Scanning acoustic microscopy (SAM) is a useful observational tool in cellular study as non-invasive living observation is feasible, unlike in conventional optical microscopy. In a previous study, cell morphological changes were successfully visualized using acoustic impedance measurements. These acoustic impedance changes correspond to cell elasticity, mainly reflecting changes in the cytoskeleton. In this study, we evaluate the elastic changes in murine breast cancer cell C127I during mitosis. C127I cells were cultured to ∼75% confluency before measurement, using a transducer with a central frequency of 320 MHz. Dynamic changes during mitosis were successfully mapped using SAM and confirmed by laser confocal microscopy. Cells in prometaphase, anaphase, and telophase, which could previously only be confirmed through immunostaining, were successfully visualized using SAM. This suggests that SAM is capable of distinguishing cells in different mitotic phases based on the changes in acoustic impedance.

Time-lapse seismic integrated with surface microseismic for SRV characterization in the Vaca Muerta Formation

Time-lapse (4D) seismic acquisitions were performed in the unconventional play of the Vaca Muerta Formation to monitor hydraulic stimulation efficiency and characterize the stimulated rock volume (SRV) in horizontal drains. Two 4D pilots were carried out by acquiring 3D surveys before and after hydraulic stimulation. The pilots targeted different stratigraphic landings characterized by distinct lithological and geomechanical properties. The 4D pilots were performed in synergy with surface microseismic acquisitions. The combined acquisition enabled joint interpretation of the results. Time-lapse acoustic inversions were performed to identify changes in acoustic impedance. They revealed the vertical dimension of the SRV more precisely than the analysis of the envelope of the wet microseismic events. These wet events are interpreted as hydraulically connected to the well. The 4D signal is interpreted as the envelope of the induced hydraulic fractures, defined here as the fractured rock volume. This volume refers to where the rock frame has been directly affected by the stimulation job. The image provided by 4D seismic represents the most direct and accurate measurement of the volume encircling the flow pathways created by the fracture network generated by the hydraulic stimulation. This information is key to assessing ultimate hydrocarbon recovery and optimizing the development of unconventional reservoirs. The added value of the microseismic is the mapping of subtle events associated with the reactivation of critically stressed faults/lineaments. These provide preferential pathways that could connect to the well. They also help in the understanding of hydraulic interactions between the wells and their individual SRVs. The findings of these studies indicate that the optimal lateral and vertical well spacing should be designed based on 4D monitoring for drainage optimization and on microseismic for the analysis of interwell structural interferences.

Ultrasonic Logging of Creeping Shale

With the end of oil production, the need for safe and economically efficient plug and abandonment (P&A) operations increases. Due to the high costs related to traditional P&A processes, the possibility of shale bonding to the well casing, forming a natural barrier, is explored. Here, we present a unique laboratory experiment of creeping shale in a pressure cell, which is monitored during the creep and bonding processes using the ultrasound pulse-echo (PE) and pitch-catch (PC) measurement techniques. The combination of continuous PE and PC measurements in one direction, with discrete measurements in 5° intervals, and the logging of confining pressure, temperature, and permeability allows an improved understanding of the bonding processes and the interpretation of parameters derived from PE and PC measurements. We find that the initial creep of the shale occurs when the confining pressure is increased from 5 to 9 MPa, resulting in significant changes observed in the acoustic impedances derived from PE and PC measurements. However, as permeability is still high, we assume that channels are still open. With the increase in confining pressure to 13 and 14 MPa, respectively, we observe a decrease in permeability corresponding to an overall decrease in signal strength for the PC data of up to 25 dB and a decrease in the PE group delay parameter of up to 0.6 μs corresponding to a change in acoustic impedance from about 1 MRayl to about 3 to 3.5 MRayl. Large variations with direction can be observed. Combining the information of PE and PC gives a good impression of the bonding processes.

A Test Method for Acoustic Emission Properties of Natural Cellulose Fiber-Reinforced Composites

To test the acoustic performance of fiber-reinforced composites for replacing wood, an acoustic vibration test method is developed. For evaluation of the test method, composites are manufactured using hemp and ramie embedded in epoxy, through vacuum-assisted resin infusion molding. The effects of the most important factors, i.e., impulse, relative humidity (RH), and specimen thickness, on the acoustic vibration response of the composites are systematically studied. The magnitudes of the impulses, represented by different masses of the dropping balls, seem to have little influence on the shapes of the acoustic vibration curves, although the intensity of the spectra increases as the impulse increases. The RH influences the spectrum shape significantly due to variation in the Young’s modulus and density of the material upon absorption of moisture. The specimen thickness also greatly affects the testing results. The specific dynamic modulus, acoustic radiation damping coefficient, and acoustic impedance change a little as the impulse magnitude and RH change, but decrease substantially as the specimen thickness increases. The specific dynamic modulus can be linearly correlated with the flexural modulus of a material.

Examination of Film Thickness Dependence on Acoustic Impedance of Gold and Chromium Thin Films by Scanning Acoustic Microscopy

Thickness induced changes in acoustic impedance of gold (Au) and chromium (Cr) thin films are studied with scanning acoustic microscopy (SAM). Thin films are produced by thermal evaporation technique on BK7 glass substrates with varying thicknesses between 40 nm to 200 nm. In acoustic impedance (AI) mode, the microscope generates two-dimensional acoustic impedance maps of the thin films and micrometer resolution helps determining the surface defects on these films. On the other hand, acoustic impedance value is found to increase as thickness increases for both Au and Cr thin films indicating increased elasticity, therefore, hardness. The mean and standard deviation values of acoustic impedance of Cr thin films were found as 1.901 ± 0.050 MRayl for 40 nm, 1.905 ± 0.045 MRayl for 80 nm, 1.943 ± 0.049 MRayl for 120 nm, 1.964 ± 0.049 MRayl for 160 nm and 1.987 ± 0.052 MRayl for 200 nm. The mean and standard deviation values of acoustic impedance of Au thin films were found as 1.725 ± 0.026 MRayl for 80 nm and 1.954 ± 0.047 MRayl for 200 nm. This success achieved by SAM, demonstrates its potential in monitoring thin film surfaces even with very small thicknesses.

Influence of cavitation on the acoustic boundary conditions in water hammer experiments

A water hammer event is created by stopping a flow in a pipeline using a fast closing valve. The pressure is measured at three different positions upstream the valve. Cavitation occurs close to the valve and is detected by vapour pressure in the pipeline. Frequencies in the liquid part of the pipe were measured and statistically evaluated in order to analyse whether cavitation acts as a boundary condition of acoustics.Without cavitation one side of the pipe is an open end, while the other side is a closed end. In presence of cavitation the cavity should act like an open end due to the high change of acoustic impedance from liquid to gaseous phase. Therefore it is expected that the oscillating behavior is changing from an open/close to an open/open system. The measured frequencies indeed show a change towards an open/open configuration. It is shown that cavitation acts as a boundary condition in this system.

Effects of volume fraction and diameter of hollow spheres on acoustic properties of Metallic-Hollow-Sphere/Polyurethane (MHSP) acoustic composites

Metallic hollow spheres and polyurethane resin are excellent sound insulation and sound absorption materials. In this study, the surface modified 316L stainless steel hollow spheres were added into polyurethane by casting method. The influence of the volume fraction and diameter of the hollow spheres on the sound insulation and sound absorption performance of the Metallic-Hollow-Sphere/Polyurethane (MHSP) acoustic composites was investigated by impedance tube method and the relevant acoustic mechanism was discussed. When the volume fraction of hollow spheres is 45% and the diameter is 2.5 mm, composite has the best sound insulation performance. And when the volume fraction of hollow spheres is 60% and the diameter is 2.5 mm, composite has the best sound absorption performance. Due to the mass effect, damping effect, change of acoustic impedance and multiple interface of composites, sound waves will reflect, refract and scatter many times in the process of propagation, thus losing lots of sound energy to improve the sound insulation performance. The sound absorption mechanism of MHSP is that the friction, viscosity and reflection of sound waves in the pores of polyurethane, cavities of the hollow spheres and interfaces will cause the loss of sound energy and turn it into heat energy.

Acoustic connection between thermoacoustic engine and impulse turbine

In this study, we studied how to connect a thermoacoustic engine (TAE) and an impulse turbine to construct a thermoacoustic generator for converting thermal energy into electric power. The thermoacoustic generator was separated into two sub-systems: (1) system A, which consisted of a looped-tube TAE and a branch tube, and (2) system B, which consisted of an impulse turbine loop and a branch tube. The sub-systems were evaluated individually using an acoustic driver to determine the driving conditions such as branch length, driving frequency, and temperature for the connected system. In system A, which included the TAE, the change in specific acoustic impedance was small with respect to the velocity amplitude. However, in system B, which included the impulse turbine, the change in specific acoustic impedance with respect to the velocity amplitude was nonlinear. The sub-systems were connected by branch pipes, whose lengths were determined from the individual sub-system evaluation results, and the device was confirmed to self-oscillate at the driving temperature. When the device was operated at the driving conditions, the frequency, velocity amplitude, and specific acoustic impedance with self-oscillation were the same as those of the individual sub-systems. This also confirms the validity of evaluating the TAE and impulse turbine separately.

Monitoring Viscosity and Total Solids Content of Milk Protein Concentrate Using an Inline Acoustic Flowmeter at Laboratory Scale.

Control of milk concentrate viscosity and total solids (TS) content prior to spray drying can improve dairy ingredient manufacture. However, the availability of hygienic and appropriately pressure rated process viscometers for inline monitoring of viscosity is limited. An acoustic flowmeter (FLOWave) is an inline process analytical technology (PAT) tool that measures changes in acoustic signals in response to changes in liquid properties (i.e., acoustic transmission (AT), acoustic impedance (AI), temperature and volume flowrate). In this study, an acoustic flowmeter is evaluated as an inline PAT tool for monitoring viscosity of milk protein concentrate (MPC85), protein and TS content of (MPC85), and standardised MPC (sMPC). Laboratory scale experiments were carried out at 45 °C for five different concentrations (4–21%) of MPC85 and sMPC. Results showed that AT decreased with an increase in MPC85 viscosity (e.g., AT was 98.79 ± 0.04% and 86.65 ± 0.17% for 4% and 21% TS content, respectively). Non-linear regression was carried out to develop a relationship between AT and offline viscosity (R2 (coefficient of determination) value = 0.97 and standard error of prediction = 1.86 mPa·s). AI was observed to increase at higher protein and TS content which was dependent on protein to total solid ratio (P_TSR). Multiple linear regression was carried out to develop the relationship between AI, protein content, TS content and P_TSR. Results demonstrated that AI could be used to monitor the protein and TS content of milk protein concentrate (R2 > 0.96). Overall this study demonstrated the potential of an inline acoustic flowmeter for monitoring process viscosity, protein and TS during dairy concentrate processing.

Properties and mechanism of a novel metallic‐hollow‐spheres/polyurethane acoustic composite

AbstractIn this article, 316L stainless steel hollow spheres (316L HS) and polyurethane (PU) resins were used to prepare a novel metallic‐hollow‐sphere/polyurethane (MHSP) acoustic composite by casting. The acoustic experimental results of this composite revealed that compared to monolithic PU, the sound transmission loss of the composites increased and the maximum sound absorption peak shifted to lower frequency with the change of acoustic impedance and resonance frequency. When the surface of metallic hollow sphere used in MHSP composite was modified by silane coupling agent, the sound insulation and sound absorption performance of MHSP composites were further improved. This is related to the addition of the molecular layer of coupling agent between MHSP matrix. In addition, the addition of silane coupling agent creates PU foaming in matrix, resulting in a large number of pores and gaps that can increase the sound waves energy loss through air friction and heat exchange.

Theoretical Optimization of Trapped-Bubble-Based Acoustic Metamaterial Performance

Acoustic metamaterials have proven to be a versatile tool for the precise control and manipulation of sound waves. One of the promising designs of acoustic metamaterials employ the arrays of bubbles and find applications for soundproofing, blast mitigation, and many others. An obvious advantage of bubble-based metamaterials is their ability to be relatively thin while absorbing low-frequency sound waves. The vast majority of theories developed to predict resonant behavior of bubble-based metamaterials capitalize on Minnaert frequency. Here, we propose a novel theoretical approach to characterize bubble-based metamaterials that are based on our previous findings for a single bubble trapped in circular cavity modeled as a thin clamped plate. We obtain analytical expressions for resonant frequencies of bubble metascreens using self-consistent approximation. Two geometry factors, distance between bubble centers and distance between bubble center and interface of acoustic impedance change, are taken into account. We demonstrate the existence of multiple bandgaps and possibility of switching between them via adjustment of geometry parameters and reflector properties.

Acoustic Behavior Prediction and Analysis of Resonators in the Presence of Low Mach Number Flow

The frequency-domain linearized Navier–Stokes equations (LNSEs) are used to describe the sound field of Helmholtz resonators and concentric perforated tube resonators in the presence of low Mach number flow. The numerical procedure of LNSEs method is performed in three steps, computational fluid dynamics (CFD) calculation, data transfer and acoustics calculation. The transmission loss predictions of the resonators exhibit good agreement with measurements published in the literature. The results show that the low Mach number flow shifts the resonance frequencies of resonators and changes the acoustic attenuation behavior, which may be attributed to the change of acoustic impedance of the opening and orifices. In order to weaken the effect of flow on the resonance frequency, the modified configurations of resonators are proposed by using the conical tubes to reduce the flow velocity passing the opening and orifices. Numerical results demonstrated that the influence of flow velocity on the resonance frequency of the modified resonators is less sensitive than the original configurations.