Acoustic Impedance Analysis Research Articles

Sound absorption performance and mechanism of aluminum foam with double-layer structures of conventional and porous cell walls

Open-cell aluminum foam exhibits sound absorption valleys in the 2500-4000 Hz range, reducing its sound absorption performance in the 800–6300 Hz range. This paper prepared a novel aluminum foam with a double-layer structure using the infiltration casting method, and its pore structure, sound absorption performance, acoustic model, and sound absorption mechanism are investigated. The double-layer structure consists of a conventional pore (CP) layer with a single pore size of 250 μm or 600 μm and a porous cell wall (PCW) layer with double pore diameters of 250 μm and 600 μm. As the thickness ratio between the CP and PCW layers decreases, the acoustic absorption valley value of the double-layer structure increases when combined with a small-pore CP layer. In contrast, it decreases slightly when combined with a large-pores CP layer. The double-layer structure reaches a sound absorption valley value and average sound absorption coefficient of 0.912 and 0.902, respectively. The double-layer structure's sound absorption valley value is better than that of a homogeneous structure, improving sound absorption performance. A Lu modified model is established to characterize the sound absorption of the double-layer structure, which closely matches the experimental results. The modified model further analyzed the vital geometrical parameters affecting the absorption valleys. Acoustic impedance analysis shows the enhanced sound absorption valleys are due to: 1) Gradient acoustic impedance reduces sound reflections at the air-structure interfaces and increases secondary reflection at the interfaces in the structure; 2) The series–parallel configuration increased the resonance peak bandwidth, while the dual-sized resonance cavities regulated the resonance peak frequency.

In-depth investigations into symmetrical labyrinthine acoustic metamaterial with two micro-slit entries for low-frequency sound absorption.

Sound absorption below 1000 Hz has been extremely difficult through traditional barriers and absorbers, but it is required for noise control of appliances and machineries. Existing passive acoustic metamaterials attenuate low-frequency noise but with narrow bandwidths and bulky sizes. Hence, this paper proposes an acoustic metamaterial with enclosed symmetrical labyrinthine air channels and two micro-slits (configuration 1, identical slits; configuration 2, unequal length slits) at the end channels. Its theoretical model is established by acoustic impedance analysis using electro-acoustic analogy and validated numerically and experimentally. Sound absorption is found to happen as a result of impedance matching, Fabry-Perot-like labyrinthine resonances, and thermo-viscous losses in micro-slits. Parametric investigations reveal that increase in the number of channels, channel length, total height, and outer panel thickness shifts sound absorption peak to lower frequency but also decreases the magnitude and frequency range of absorption. Decreasing the channel width and slit width increases the sound absorption magnitude without changing absorption frequencies. Interestingly, unequal slit lengths perform better than equal slits by giving a lower frequency sound absorption with increased magnitude and frequency range, which is unlike that in existing labyrinthine metamaterials. Therefore, the proposed unequal slit metamaterial has enhanced low-frequency sound absorption and can be applied to appliances and machineries.

Ultrathin acoustic metamaterial as super absorber for broadband low-frequency underwater sound

In this work, an ultrathin acoustic metamaterial formed by space-coiled water channels with a rubber coating is proposed for underwater sound absorption. The proposed metamaterial achieves perfect sound absorption (alpha > 0.99) at 181 Hz, which has a deep subwavelength thickness (lambda {/}162). The theoretical prediction is consistent with the numerical simulation, which demonstrate the broadband low-frequency sound absorption performance of the proposed super absorber. The introduction of rubber coating leads to a significant decrease of the effective sound speed in the water channel, resulting in the phenomenon of slow-sound propagation. From the perspective of numerical simulations and acoustic impedance analysis, it is proved that the rubber coating on the channel boundary causes slow-sound propagation with inherent dissipation, which is the key to meet the impedance matching condition and achieve perfect low-frequency sound absorption. Parametric studies are also carried out to investigate the effect of specific structural and material parameters on sound absorption. By tailoring key geometric parameters, an ultra-broadband underwater sound absorber is constructed, with a perfect absorption range of 365–900 Hz and a deep subwavelength thickness of 33 mm. This work paves a new way for designing underwater acoustic metamaterials and controlling underwater acoustic waves.

A study of low frequency sound insulation mechanism of a perforated plate-type acoustic metamaterial

This paper presents a new design of a perforated plate-type acoustic metamaterial (PAM) to evade the influence of membrane pre-tension on the acoustic performance of metamaterials and to enable air ventilation while achieving the designated sound insulation. The study embarks on the analysis of sound insulation mechanism of a typical perforated membrane-type acoustic metamaterial (MAM) from the acoustic context, and discloses that sound transmission loss (STL) peaks of a perforated MAM are due to the strong wave interference between sound sources transmitted through the orifice(s) and the membrane(s). The sound insulation mechanism is explored further in the study by an acoustic impedance analysis of a perforated metamaterial using an electro-acoustic analogy in the latter part of the paper, and the result confirms that the STL peaks of a perforated PAM (or MAM) are indeed the outcome of a strong sound interference. The study also compares an experiment test and a finite element simulation on the sound transmission of a perforated PAM based on the new design. The result confirms that the new perforated PAM can yield a good broadband STL at relatively low frequencies. A practical application using the perforated PAM design is applied to reduce the noise propagation from the compressor compartment of a commercial refrigerator. The test result verifies the effectiveness of the design in terms of both sound reduction and air ventilation.

Seismic Attributes Analysis as a Precursor for Hydrocarbon Indication: A Case Study of Onshore Fuba field, Niger Delta, Nigeria

Seismic attributes analysis as a precursor for hydrocarbon indication in onshore Fuba Field, Niger Delta, Nigeria using Well-logs and 3D Seismic data are here presented. Well-to-seismic ties, faults and horizon mapping, time-surface generation, depth conversion and seismic attributes generation were carried out using Petrel software. The structural interpretation of seismic data reveal highly synthetic and antithetic faults which are in line with faults trends identified in the Niger Delta. Of the 36 interpreted faults, only synthetic and antithetic faults are regional, running from the top to bottom across the field. These faults play significant roles in trap formation at the upper, middle and lower sections of the field. Three distinct horizons were mapped. Reservoir M is found at a shallower depth from 10937 to 10997 ft, reservoir N is found at a depth ranging from 11213 to 11241 ft while reservoir O is found at a deeper depth ranging from 11681 to 11871 ft respectively. Analysis of the relevant seismic attributes such as variance edge, root mean square, maximum amplitude and relative acoustic impedance were applied to the seismic data. The variance values ranges from 0.0 to 1.0. The Variance edge analysis was used to delineate the prominent and subtle faults in the area. The RMS amplitude values ranges from 9,000 to 13,000 in the reservoirs. The root mean square amplitude and maximum amplitude analysis reveal bright spot anomaly. These amplitude anomalies served as direct hydrocarbon indicators (DHIs), unravelling the presence and possible hydrocarbon prospective zones. The relative acoustic impedance analysis was used for delineating lithology variation in the seismic sections. Results from this study have shown that away from the currently producing zone of the field, additional leads and prospects exist, which could be further evaluated for hydrocarbon production.

Anion Exchange and Water Dynamics in a Phosphonium-Based Alkaline Anion Exchange Membrane Material for Fuel Cells: An Electrochemical Quartz Crystal Microbalance Study.

The anion exchange and water dynamics of a phosphonium-based alkaline anion exchange membrane (AAEM) during the methanol oxidation process have been studied with the electrochemical quartz crystal microbalance (EQCM). The viscoelastic effects of the phosphonium-based AAEM in water and the optimal film thickness for EQCM analysis were identified by acoustic impedance analysis. The phosphonium-based AAEM exhibited stronger mechanical toughness in water when compared to a quaternary-ammonium-based membrane that was studied previously. From the simultaneous measurement of the electrochemical response and the frequency changes of the quartz crystal oscillator, water ingress/egress to/from the AAEM film was found to accompany the hydrogen adsorption/desorption, Pt oxidation process, and methanol oxidation process. The in situ study of AAEM films helps illustrate the critical role that water transport plays in electrochemical processes during the operation of anion exchange membrane fuel cells. The generated CO32- and HCOO-, during methanol oxidation, were absorbed into the AAEM film, replacing the OH- in the film, as shown by the decrease in frequency after one potential cycle. The exchange of OH- by CO32- and HCOO- was found to be reversible. These results provide insights into the anion exchange processes in membranes and emphasize the importance of characterizing the hydrated membranes under electrochemical conditions.

Use of Ultrasound Microscopy for Ex Vivo Analysis of Acoustic Impedance in Mouse Liver with Steatohepatitis

Scanning acoustic microscopy reveals information on histology and acoustic impedance through tissues. The objective of the present study was to investigate whether acoustic impedance values in the liver over time reflect the progression of steatohepatitis through different grades and stages, and whether this approach can visualize histologic features of the disease. Mice were divided into two groups: a control group and a steatohepatitis group prepared by keeping the mice on a methionine and choline-deficient diet for 56 weeks. The hepatic lobe was excised for measurement of impedance and observation of microscopic structure using a commercially available scanning acoustic microscopy system with a central frequency of 320 MHz. Scanning acoustic microscopy revealed that acoustic impedance through liver tissue with steatohepatitis temporarily decreased with the degree of fat deposition and then increased in parallel with the progression of inflammation and fibrosis. However, the acoustic images obtained did not allow discrimination of detailed microstructures from those seen using light microscopy. In conclusion, estimation of acoustic impedance appears to have potential clinical applications, such as for monitoring or follow-up studies.

Identification of seismic attributes for hydrocarbon prospecting of Akos field, Niger Delta, Nigeria

In this study, we have extracted and analyzed four seismic attributes of Akos oil field to obtain more information about the structures, stratigraphy and hydrocarbon potential of the Akos field from available seismic and a suite of well logs data. Two lithology and reservoirs were delineated from the well logs. Two horizons and growth faults were identified in the seismic sections. For a comprehensive analysis of the structural and stratigraphic understanding of the reservoirs, four seismic attributes variance edge, sweetness, root mean square and relative acoustic impedance were applied to the seismic data. The Variance edge analysis was used to delineate the prominent and subtle faults in the area. The high sweetness regions in the seismic data indicate high amplitude which indicates the presence of hydrocarbon-bearing sand units. The root mean square amplitude analysis also indicates the presence of hydrocarbon in seismic data. The relative acoustic impedance analysis was used for delineating lithology variation in the seismic sections. The result of the seismic attribute analysis has shown that the Akos field has good hydrocarbon prospects.

Wet subglacial bedforms of the NE Greenland Ice Stream shear margins

AbstractWe describe elongate, wet, subglacial bedforms in the shear margins of the NE Greenland Ice Stream and place some constraints on their formation. Lateral shear margin moraines have been observed across the previously glaciated landscape, but little is known about the ice-flow conditions necessary to form these bedforms. Here we describe in situ sediment bedforms under the NE Greenland Ice Stream shear margins that are observed in active-source seismic and ground-penetrating radar surveys. We find bedforms in the shear margins that are ~500 m wide, ~50 m tall, and elongated nearly parallel to ice-flow, including what we believe to be the first subglacial observation of a shear margin moraine. Acoustic impedance analysis of the bedforms shows that they are composed of unconsolidated, deformable, water-saturated till. We use these geophysical observations to place constraints on the possible formation mechanism of these subglacial features.

Modeling and experimental investigation of a free-piston Stirling engine-based micro-combined heat and power system

In recent years, combined heat and power (CHP) systems have attracted increasing attention worldwide. Owing to their advantages of high overall thermal efficiency, fuel flexibility, low noise and vibration, and low emissions, Stirling engines, especially dynamic Stirling engines (i.e., free-piston Stirling engines, FPSEs) are promising candidates for micro-CHP systems. In this paper, recent progress in Stirling engine-based micro-CHP systems and FPSE modeling and analysis is first briefly reviewed, and then a hybrid calculation model based on thermoacoustic theory is proposed and developed to simulate the entire micro-CHP system. Finally, the construction and testing of a pilot setup is described in detail. The obtained experimental results clearly validate the numerical model and scheme, with the primary deviation within approximately 10%. CHP performance tests revealed a maximum CHP efficiency of 87.5% and an output electrical power of 2.9 kW, corresponding to a 28% thermal-to-electric efficiency, when the delivering temperature was above 60 °C. Furthermore, acoustic impedance analysis indicated that the CHP efficiency remains high over a large temperature lift, which was also confirmed experimentally.

基于Virtual.Lab Acoustics的管道壁面声阻抗优化分析

基于Virtual.Lab Acoustics的管道壁面声阻抗优化分析

Acoustic Impedance Analysis with High-Frequency Ultrasound for Identification of Fatty Acid Species in the Liver

Acoustic properties of free fatty acids present in the liver were studied as a possible basis for non-invasive ultrasonic diagnosis of non-alcoholic steatohepatitis. Acoustic impedance was measured for the following types of tissue samples: Four pathologic types of mouse liver, five kinds of FFAs in solvent and five kinds of FFAs in cultured Huh-7 cells. A transducer with an 80-MHz center frequency was incorporated into a scanning acoustic microscopy system. Acoustic impedance was calculated from the amplitude of the signal reflected from the specimen surface. The Kruskal–Wallis test revealed statistically significant differences (p < 0.01) in acoustic impedance not only among pathologic types, but also among the FFAs in solvent and in cultured Huh-7 cells. These results suggest that each of the FFAs, especially palmitate, oleate and palmitoleate acid, can be distinguished from each other, regardless of whether they were in solution or absorbed by cells.

Evolution analysis of miocene channels and faults in offshore area of Strait of Hormuz (Eastern part of Persian Gulf) using seismic meta-attributes

Tectonic movement of Oman Orogeny and Zagros Orogeny and Hormuz Salt triggering are accompanied with presence of complex structures in Strait of Hormuz sedimentary basin. Geological model Obtained via multi-attribute analysis and the extracted geobodies are used to define type and relative age of channels and faults in offshore area of Strait of Hormuz (Eastern part of Persian Gulf). In this study, channels and faults were mapped using meta-attributes by a neural network. The probability volume helps more accurate extraction of channel bodies and fault planes. The channel bodies and fault planes can be revealed more continuous with dominant edges and subtle flexures as obtained results based on meta-attributes. Considering this approach, three distinct channel types (small (S), median (M) and large (L)) are illustrious in different substrates based on various flow powers that extended from West to East. Normal fault band with the NorthEast-SouthWest trend and few dip toward the East, whereas faulting may occur during late Mid Miocene- Early Upper Miocene. The main channels (M) and (L) are located on both sides of the fault in lower and upper deeps within Mid Miocene Mishan Formation sediments, while channels (S) located away from the fault within Upper Miocene-Pliocene Aghajari Formation sediments. Processes of sediment transport are very different in Miocene Aghajari and Mishan Formations as form of meandering channels and their slopes are dissimilar. Sediment supply has led to changing geometry of meandering channel due to effects of sea-level change. Based on seismic attribute study, slope and form of channel (M) has been affected by later faulting, whereas slope and form of channel (L) operated independently. Presence of meandering channel (M) with lower slope and higher sinuosity ratio in comparison with meandering channel (L) suggests that channels located in upper horizons of sedimentary basin could be consider as an appropriate place for hydrocarbon accumulation in intra Mid Miocene Mishan Formation. Furthermore, revealed channels within Mid Miocene Mishan Formation sediments are bigger than the channels within Upper Miocene-Pliocene Aghajari Formation. Reservoir properties study suggests that channel filled sediments are relatively porous than their backgrounds, producing relatively higher reservoir potential based on the integrated analysis of acoustic impedance and frequency content.

Nonlinear multichannel impedance inversion by total-variation regularization

The analysis of acoustic impedance (AI) allows for the mapping of seismic reflection data to lithology, and hence it plays an important role in the interpretation of poststack seismic data. The AI is obtainable from the inversion of the earth reflectivity series. Efficient deconvolution methods have been developed for recovering the reflectivity series from band-limited poststack data, which are multiple free, zero offset, and migrated. However, calculation of the AI from the reflectivity, when considering the spatial correlation of the impedance parameters, demands the solution of a constrained nonlinear inverse problem. Two efficient algorithms are proposed for solving the nonlinear impedance problem in multichannel form with the total-variation (TV) constraint to recover impedance maps with blocky structures. The first uses the continuous earth model for reflectivity, which allows linearizing the problem in the logarithm domain. The second uses the discrete (layered) earth model for reflectivity. In this case, a nonlinear problem is solved in the original domain. The main properties of the algorithms, which are built based on the split-Bregman technique and the discrete cosine transform are as follows: (1) They are multichannel inversion procedures, so they respect the spatial and temporal correlation of the data, (2) they impose the TV constraint on the parameters to generate blocky structures, (3) they are fast such that a large 3D impedance model with a blocky structure can be recovered easily on a personal computer, and (4) the computational complexities of both algorithms are the same. Numerical tests using simulated 2D data obtained from a benchmark Marmousi model and also 2D and 3D field data confirmed that the proposed algorithm generates more accurate with higher resolution impedance models compared with the conventional methods.

1J1-2 Acoustic Impedance Analysis with Ultra-high Frequency Ultrasound for Fatty Acid Species Identification in NASH Liver

1J1-2 Acoustic Impedance Analysis with Ultra-high Frequency Ultrasound for Fatty Acid Species Identification in NASH Liver

An Electrochemical Quartz Crystal Microbalance Study of a Prospective Alkaline Anion Exchange Membrane Material for Fuel Cells: Anion Exchange Dynamics and Membrane Swelling

A strategy has been devised to study the incorporation and exchange of anions in a candidate alkaline anion exchange membrane (AAEM) material for alkaline fuel cells using the electrochemical quartz crystal microbalance (EQCM) technique. It involves the electro-oxidation of methanol (CH3OH) under alkaline conditions to generate carbonate (CO3(2-)) and formate (HCOO(-)) ions at the electrode of a quartz crystal resonator coated with an AAEM film, while simultaneously monitoring changes in the frequency (Δf) and the motional resistance (ΔR(m)) of the resonator. A decrease in Δf, indicating an apparent mass increase in the film, and a decrease in ΔR(m), signifying a deswelling of the film, were observed during methanol oxidation. A series of additional QCM experiments, in which the effects of CH3OH, CO3(2-), and HCOO(-) were individually examined by changing the solution concentration of these species, confirmed the changes to be due to the incorporation of electrogenerated CO3(2-)/HCOO(-) into the film. Furthermore, the AAEM films were found to have finite anion uptake, validating the expected tolerance of the material to salt precipitation in the AAEM. The EQCM results obtained indicated that HCOO(-) and CO3(2-), in particular, interact strongly with the AAEM film and readily displace OH(-) from the film. Notwithstanding, the anion exchange between CO3(2-)/HCOO(-) and OH(-) was found to be reversible. It is also inferred that the film exhibits increased swelling in the OH(-) form versus the CO3(2-)/HCOO(-) form. Acoustic impedance analysis of the AAEM-film coated quartz resonators immersed in water showed that the hydrated AAEM material exhibits significant viscoelastic effects due to solvent plasticization.

DNA aptamer configuration affects the sensitivity and binding kinetics of thrombin

DNA aptamer configuration affects the sensitivity and binding kinetics of thrombinThrombin is serine protease involved in the coagulation cascade, which converts soluble fibrinogen into insoluble strands of fibrin - a matrix of the blood clot formation. Development of the sensitive method of the thrombin detection in nanomolar level is important for clinical practice. In this work we applied acoustic thickness shear mode method (TSM) for study the binding of human thrombin depending on DNA aptamer configuration. We compared sensitivity of detection and binding kinetics of the thrombin to the conventional DNA aptamers and aptamer dimers immobilized at the surface of quartz crystal transducer. We have shown that aptasensors based on aptamer dimers more sensitively detect thrombin. The aptamer-thrombin complexes were also more stable as revealed from equilibrium dissociation constant,KD, that was 4 times lower for aptamer dimers in comparison with conventional aptamers. Determination of motional resistance,Rm, from acoustic impedance analysis allowed us to find important differences in physico-chemical properties of layers formed by conventional aptamers and aptamer dimers.

Micromechanical Investigations on Films made of Recombinant Spider Silk Proteins and Silk Fibroin

ABSTRACTFilms made of a recombinant spider silk protein and silk fibroin were prepared by spincoating and casting. Therefore the solubility of these substances was investigated in hexafluoroisopropa-nol, ionic liquids and concentrated salt solutions. The roughness and the thickness of the protein films were determined by the Atomic Force Microscopy (AFM) and by mechanical profilometry. The micromechanical behaviour was investigated by acoustic impedance analysis using a quartz crystal microbalance (QCMB) as well as by microindentation. Films with thickness less than 350 nm revealed an almost ideal elastic behaviour in the range of 5 to 75 MHz. At a higher film thickness the half-band-half width increases considerably and the films show a viscoelastic be-haviour with a considerable dissipation. The relative humidity significantly influences the me-chanical behaviour of protein films. Hence the micro-hardness and the ability of water adsorption were determined in dependence on the relative humidity.

Preparation and mechanical properties of layers made of recombinant spider silk proteins and silk from silk worm

Layers of recombinant spider silks and native silks from silk worms were prepared by spin-coating and casting of various solutions. FT-IR spectra were recorded to investigate the influence of the different mechanical stress occurring during the preparation of the silk layers. The solubility of the recombinant spider silk proteins SO1-ELP, C16, AQ24NR3, and of the silk fibroin from Bombyx mori were investigated in hexafluorisopropanol, ionic liquids and concentrated salt solutions. The morphology and thickness of the layers were determined by Atomic Force Microscopy (AFM) or with a profilometer. The mechanical behaviour was investigated by acoustic impedance analysis by using a quartz crystal microbalance (QCMB) as well as by microindentation.

Simultaneous determination of the mechanical moduli and mass of thin layers using nonadditive quartz crystal acoustic impedance analysis

High frequency rheological properties of polymer films have been measured using a nonadditive quartz crystal resonator impedance approach. The method involves fast measurement of the quartz covered with the film in contact with solutions of different viscosities and the measurement of the equivalent impedance of the bare quartz resonator in contact with the same solutions. Although by using a standard quartz crystal acoustic impedance method it is not possible to determine more than two of the four film parameters (density, thickness, storage modulus G′, and loss modulus G″), we demonstrate that the interaction between the film under study and a semi-infinite layer of liquid gives the additional information needed to get the mechanical moduli G′ and G″ simultaneously with the mass or thickness of the film. An alternative approach to measure G′ and G″, which involves independent and very precise determination of the film thickness, is discussed. Experimental measurements of polystyrene using dioctyl phthalate as a plasticizer show excellent agreement with Martin’s model for quartz resonators covered with viscoelastic nonpiezoelectric layers. The results demonstrate that quartz resonators can be used to measure high frequency rheological properties of films simply without the need of an independent measurement of thickness.