Sinusoidal Pressure Research Articles

Analytical and experimental study of failure onset during a Brazilian test

The location of the failure initiation in the Brazilian test is strongly influenced by the contact angle created in the loaded area. As this angle increases, the position of the initial failure point is closer to the center of the disc, which is a result of both: uniform radial pressure and sinusoidal radial pressure; as well as adopting different failure criteria and materials. Moreover, the frictional stresses throughout the contact between the jaw (or platens) and the disc cannot be considered as a critical failure parameter for failures initiated from the origin to a radial distance of 0.8R.In this paper, firstly, the influence of the above mentioned parameters in the location of the initial failure point was analytically studied. Secondly, the analytical results have been proven through experimental tests. Finally, once the importance of the contact angle in the location of the initiation point was checked, a procedure is suggested in order to increase the contact angle with the same load applied to one specific sample, by using various jaw curvatures.The location of failure initiation does not cause great disturbances in the determination of the indirect tensile strength. However, the position is important in order to adjust the failure criteria in the tension region. According to the location of the initial failure, the stress field in terms of principal stresses (σ1 and σ3) will be different. So by knowing this position, the precise failure criteria could be established in σ1 - σ3, specifically in the tension region. Meaning that as well as the triaxial test is mostly used to calculate the failure criteria in the compression region, the Brazilian test could be used to obtain the limiting stress states in the tension region.

Hepatic transudation barrier properties.

Fluid and protein continuously transude from the surface of the liver. Despite a common understanding that transudation plays a critical role in hepatic interstitial and peritoneal fluid balance, transudation from the entire liver has not been studied. Therefore, the goal of the present work was to provide the first direct measurement of the hepatic transudation rate and transudation barrier properties. Transudation rates were determined by collecting transudate from the entire liver. Hydraulic conductivity, and fluid transudation and protein reflection coefficients of the transudation barrier (formed by the subscapular interstitial matrix, capsule, and peritoneum) were determined from changes in fluid and protein transudation rates in response to hepatic venous pressure elevation. Following hepatic venous pressure elevation from 6.1±0.9 to11.1±0.6mm Hg, transudation rate increased from 0.13±0.03 to 0.37±0.03 mL/min·100g. Transudation barrier hydraulic conductivity, fluid transudation and protein reflection coefficients (3.9×10-4 ±5.7×10-5 mL/min·mm Hg·cm2 , 0.36±0.04mL/min·mm Hg, and 0.09±0.03, respectively) were comparable to those reported for hepatic sinusoids. Taken together, these findings suggest that the hepatic transudation barrier is highly permeable at elevated sinusoidal pressures. These fundamental studies provide a better understanding of the hepatic transudation barrier properties and transudation under conditions that are physiologically and clinically relevant to ascites formation.

Transient effects in the translation of bubbles insonated with acoustic pulses of finite duration

The translation of a bubble under the action of an acoustic forcing finds applications in fields ranging from drug delivery to sonoluminescence. This phenomenon has been widely studied for cases where the amplitude of the forcing remains constant over time. However, in many practical applications, the duration of the forcing is not long enough for the bubble to attain a constant translational velocity, mainly due to the effect of the history force. Here, we develop a formulation, valid in the limit of very viscous flow and small-amplitude acoustic forcing, that allows us to describe the transient dynamics of bubbles driven by acoustic pulses consisting of finite numbers of cycles. We also present an asymptotic solution to this theory for the case of a finite-duration sinusoidal pressure pulse. This solution takes into account both the history integral term and the transient period that the bubble needs to achieve steady radial oscillations, the former being dominant during most of the acceleration process. Moreover, by introducing some additional assumptions, we derive a simplified formula that describes the time evolution of the bubble velocity fairly well. Using this solution, we show that the convergence to the steady translational velocity, given by the so-called Bjerknes force, occurs rather slowly, namely as $\unicode[STIX]{x1D70F}^{-1/2}$, where $\unicode[STIX]{x1D70F}$ is the time made dimensionless with the viscous time scale of the bubble, which explains the slow convergence of the bubble velocity and stresses the importance of taking the history force into account.

Nonspherical sub-millimeter gas bubble oscillations: Parametric forcing and nonlinear shape mode coupling

The nonspherical oscillations of a gas bubble being forced by a sinusoidal pressure field in an axisymmetric geometry are considered using an asymptotic model, which accounts for nonlinear shape mode interactions to third order, the effects of viscosity (in the absence of vorticity) to the same order, and weak compressibility. In particular, conditions by which a parametrically forced sub-millimeter sized bubble can achieve stable oscillatory shape deformation are studied in detail. It is found that a combination of the transfer of energy from the parametrically forced shape mode to the other modes through nonlinear shape mode coupling and viscous damping is key. Two transition regions in the spherical oscillations of the bubble are identified, the first being a consequence of the damping effects of compressibility and viscosity (with compressibility acting on a faster time scale) and the second due to nonlinear shape mode interactions. During this second transition time interval, the parametrically forced shape mode grows rapidly and nonlinearly excites other shape modes. For the moderate driving pressures considered, this growth is shown to peak and following a stabilizing transition region (only observed for the n ≥ 3 shape modes), the bubble thereafter undergoes stable, oscillatory shape deformation. Though the resultant shape deformation is dominated by the parametrically forced mode n = i, it is found to be a combination of a number of shapes modes, where the next most important mode is the second harmonic, n = 2i shape mode.

Design of a continuous wave mud pulse generator for data transmission by fluid pressure fluctuation

High-speed downhole transmission technology is in high demand for measurement while drilling (MWD) and logging while drilling (LWD) systems which have had major roles in increasing the geo-steering and formation evaluation capacity of reach wells, difficult horizontal wells and branch wells as well as increasing drilling rates. This paper presents the conceptual design and performance of a novel continuous wave mud pulse generator with the goal of transmitting data using hydraulic pressure waves. The generator includes the rotary valve, drive shaft and bearings, rotary and static seals, motor and reducer, resolver, pressure balance structure and lower centralizer; all of these components are mounted within a rotary drill collar. In particular, the rotary valve is the key important part of the continuous wave mud pulse generator. Based on the concept of a sinusoidal signal output, an improved arc-fillet-line triangular valve orifice is designed according to the relationships between the fluid differential pressure of a thin-walled cutting edge and the fluid flow area calculated from the relative rotation angle of the rotor to the stator through the established polar coordinate equations. The highly similar sinusoidal pressure signals can be achieved by optimized valve structures, which were verified by computational fluid dynamics (CFD) simulations, where the valve flow pattern characteristics and the impact law between the gap of the stator/rotor and pressure waveform were also obtained. Moreover, the drive capability response curves of the motor driver unit with and without a load are precisely determined, and current ground hydraulic experiments indicate that the designed continuous wave mud pulse generator performs well as a whole. The generated real pressure waves exhibit clear spectrum structures with a distinctive characteristic signal.

Numerical study of acoustically driven bubble cloud dynamics near a rigid wall

The dynamics of a bubble cloud excited by a sinusoidal pressure field near a rigid wall is studied using a novel Eulerian/Lagrangian two-phase flow model. The effects of key parameters such as the amplitude and frequency of the excitation pressure, the cloud and bubble sizes, the void fraction, and the initial standoff distance on the bubbles’ collective behavior and the resulting pressure loads on the nearby wall are investigated. The study shows that nonlinear bubble cloud dynamics becomes more pronounced and results in higher pressure loading at the wall as the excitation pressure amplitude increases. The strongest collective bubble behavior occurs at a preferred resonance frequency. At this resonance frequency, pressure peaks orders of magnitudes higher than the excitation pressure result from the bubble interaction when the amplitude of the pressure excitation is high. The numerically obtained resonance frequency is significantly different from the reported natural frequency of a spherical cloud derived from linear theory, which assumes small amplitude oscillations in an unbounded medium. At high amplitudes of the excitation, the resonance frequency decreases almost linearly with the ratio of excitation pressure amplitude to ambient pressure until the ratio is larger than one.

The carotid baroreflex modifies the pressor threshold of the muscle metaboreflex in humans.

The purpose of the present study was to test our hypothesis that unloading the carotid baroreceptors alters the threshold and gain of the muscle metaboreflex in humans. Ten healthy subjects performed a static handgrip exercise at 50% of maximum voluntary contraction. Contraction was sustained for 15, 30, 45, and 60 s and was followed by 3 min of forearm circulatory arrest, during which forearm muscular pH is known to decrease linearly with increasing contraction time. The carotid baroreceptors were unloaded by applying 0.1-Hz sinusoidal neck pressure (oscillating from +15 to +50 mmHg) during ischemia. We estimated the threshold and gain of the muscle metaboreflex by analyzing the relationship between the cardiovascular responses during ischemia and the amount of work done during the exercise. In the condition with unloading of the carotid baroreceptors, the muscle metaboreflex thresholds for mean arterial blood pressure (MAP) and total vascular resistance (TVR) corresponded to significantly lower work levels than the control condition (threshold for MAP: 795 ± 102 vs. 662 ± 208 mmHg and threshold for TVR: 818 ± 213 vs. 572 ± 292 kg·s, P < 0.05), but the gains did not differ between the two conditions (gain for MAP: 4.9 ± 1.7 vs. 4.4 ± 1.6 mmHg·kg·s-1·100 and gain for TVR: 1.3 ± 0.8 vs. 1.3 ± 0.7 mmHg·l-1·min-1·kg·s-1·100). We conclude that the carotid baroreflex modifies the muscle metaboreflex threshold in humans. Our results suggest the carotid baroreflex brakes the muscle metaboreflex, thereby inhibiting muscle metaboreflex-mediated pressor and vasoconstriction responses.NEW & NOTEWORTHY We found that unloading the carotid baroreceptors shifts the pressor threshold of the muscle metaboreflex toward lower metabolic stimulation levels in humans. This finding indicates that, in the normal loading state, the carotid baroreflex inhibits the muscle metaboreflex pressor response by shifting the reflex threshold to higher metabolic stimulation levels.

A three-dimensional cell culture device for simulation of hepatic hypertension.

Hepatic stellate cells (HSCs) play a crucial role in the development of liver fibrosis which is characterized by massive tissue scarring, elevated hepatic sinusoidal pressure, and portal hypertension. However, while a multitude of chemical factors have been investigated in the pathogenesis of liver fibrosis, physical factors such as elevated hydrostatic pressure and shear stress caused by blood flow in sinusoids remain unclear. In this study, we developed a three-dimensional (3D) cell culture microfluidic platform that mimics the physical environments of hepatic sinusoids to investigate the effects of elevated hydrostatic pressure on HSCs phenotypes.

Expected sliding distance of vertical slit caisson breakwater

Evaluating the expected sliding distance of a vertical slit caisson breakwater is proposed. Time history for the wave load to a vertical slit caisson is made. It consists of two impulsive wave pressures followed by a smooth sinusoidal pressure. In the numerical analysis, the sliding distance for an attack of single wave was shown and the expected sliding distance during 50 years was also presented. Those results were compared with a vertical front caisson breakwater without slit. It was concluded that the sliding distance of a vertical slit caisson may be over-estimated if the wave pressure on the caisson is evaluated without considering vertical slit.

Modeling of a Ne/Xe dielectric barrier discharge excilamp for improvement of VUV radiation production

This work is devoted to excimer lamp efficiency optimization by using a homogenous discharge model of a dielectric barrier discharge in a Ne−Xe mixture. The model includes the plasma chemistry, electrical circuit, and Boltzmann equation. In this paper, we are particularly interested in the electrical and kinetic properties and light output generated by the DBD. Xenon is chosen for its high luminescence in the range of vacuum UV radiation around 173 nm. Our study is motivated by interest in this type of discharge in many industrial applications, including the achievement of high light output lamps. In this work, we used an applied sinusoidal voltage, frequency, gas pressure, and concentration in the ranges of 2–8 kV, 10–200 kHz, 100–800 Torr, and 10–50%, respectively. The analyzed results concern the voltage V p across the gap, the dielectric voltage V d, the discharge current I, and the particles densities. We also investigated the effect of the electric parameters and xenon concentration on the lamp efficiency. This investigation will allow one to find out the appropriate parameters for Ne/Xe DBD excilamps to improve their efficiency.

System level modeling and design maps of PMUTs with residual stresses

We report a system level approach for design of Piezoelectric Micromachined Ultrasonic Transducers (PMUTs) with inclusion of residual tension. A multilayered circular plate model is used to derive the vibrational response of a PMUT subjected to, first a sinusoidal voltage input and second, a sinusoidal pressure load with frequencies near the first resonance of the PMUT. The model is simplified with the introduction of mode shape dependent nondimensional parameters that are found to change very little over a large range of design parameters. Introduction of these parameters leads to a tractable formulation for the forced response of the PMUT. Lumped model approach is used to derive expressions for overall performance parameters in terms of transfer functions of a PMUT acting as a transmitter, a receiver and a transceiver. These transfer functions are further used to develop parametric design maps of a PMUT with a given layer configuration (material and thickness of all layers) that enable us to easily track the effect of residual tension, vibrating area and the fundamental resonant frequency of the PMUT on the figure of merit in each of the three cases. Transition of PMUTs from plate regime to membrane regime on introduction of tensile residual stresses and corresponding difference in scaling of figure-of-merits with size have been verified experimentally. Using the design maps, we arrive at clear design inferences for a PMUT and show the difference in functional relationships between performance parameters and design parameters for plate type PMUTs and membrane type PMUTs.

Anti‐Ascites Adaptation of Liver to Sinusoidal Hypertension

The hepatic capsule is highly permeable to water and proteins. Increases in sinusoidal pressure as low as 1 mmHg have been reported to significantly elevate transudation across the capsule into the peritoneal cavity under normal conditions. However, despite the fact that hepatic sinusoidal and interstitial fluid pressures are significantly elevated with cirrhosis, transudation across the capsule is minimal and there is a lack of ascites. Because hepatic lymphatic vessels and thoracic ducts are enlarged and lymph flows are several times higher than normal levels, lack of ascites in compensated cirrhosis has been commonly ascribed to enhanced hepatic lymph flow. However, changes in capsular properties have yet to be investigated thoroughly. Therefore, the purpose of this study was to evaluate our hypothesis that sustained sinusoidal hypertension leads to decrease in capsular permeability and transudation rate. Capsular hydraulic conductance, reflection coefficient, transudation rate and hepatic lymph flow rate were evaluated following short‐term (2–3 weeks; StSH) and long term (5–6 weeks; LtSH) exposure to sinusoidal hypertension. Although hepatic capsular transudation and lymph flow rates were elevated in both groups, capsular hydraulic conductance and the transudation rate were lower and the reflection coefficient was higher in LtSH. Furthermore, comparison of hepatic interstitial fluid pressure‐lymph flow and hepatic interstitial fluid pressure‐transudation relationships revealed decreased sensitivity of capsular transudation to changes in hepatic interstitial fluid pressure in LtSH. Taken together, these findings suggest that adaptation of hepatic capsule precedes the enlargement of the hepatic lymphatic vessels and may primarily be responsible for the lack of ascites in compensated cirrhosis.

Mathematical model and optimum design approach of sinusoidal pressure wave generator for downhole drilling tool

• A model is proposed for the structure of sinusoidal pressure wave generator. • An optimum design for the generator is proposed based on CFD analysis. • Optimum generator design can reduce the risks of clogging and generate sinusoidal wave. • Simulation and experimental results validate the effectiveness of the method. Mud pulse generators have been widely used for the real-time transmission of valuable directional and formation data from downholes with depths of thousands of meters. There have been numerous studies on the design of mud pulse generators in which the pressure waves were typically nonsinusoidal. Sinusoidal waves provide improved long-distance data transmission and signal noise suppression compared with nonsinusoidal waves. Although sinusoidal pressure wave generators have been studied in the published literature, the influence of the risks of clogging on the design of the generator for producing sinusoidal pressure waves has rarely been considered. To generate sinusoidal pressure waves and to reduce the risks of clogging, a mathematical model for the design of a sinusoidal pressure wave generator is developed in this paper. The effects of the axial and radial clearances between the rotor and stator on the design of the generator are considered in the model. An optimum design method for the generator is provided by combining the developed model and a computational fluid dynamics analysis. Finally, an experimental platform was built and experiments at frequencies 2 Hz and 10 Hz were conducted to validate the design result. The simulation and experimental results show that the optimized pressure waves closely approximate sine waves. Therefore, the developed mathematical model and optimization approach can be used to design a sinusoidal pressure wave generator.

Refractometry-based air pressure sensing using glass microspheres as high-Q whispering-gallery mode microresonators

In this work a refractometric air pressure sensing platform based on spherical whispering-gallery mode microresonators is presented and analyzed. The sensitivity of this sensing approach is characterized by measuring the whispering-gallery mode spectral shifts caused by a change of air refractive index produced by dynamic sinusoidal pressure variations that lie between extremes of ±1.8kPa. A theoretical frame of work is developed to characterize the refractometric air pressure sensing platform by using the Ciddor equation for the refractive index of air, and a comparison is made against experimental results for the purpose of performance evaluation.

Additive Effects of Sinusoidal Lower Body Negative Pressure on Cardiovascular Responses.

Sinusoidal lower body negative pressure (SLBNP) has been used to investigate the cardiovascular response to slow periodic changes in blood shifts, but measurements of slow fluctuations take a long time if measured for each period of SLBNP separately. Our study aimed to investigate whether the cardiovascular responses to superimposed SLBNP (S-SLBNP), which is expected to reduce the measurement time, are different from responses measured individually. S-SLBNP was configured by superimposing two conventional SLBNPs (C-SLBNP) at 180-s and 30-s periods in the pressure range from 0 to -25 mmHg. As the S-SLBNP has double the static load of C-SLBNP, we also used offset SLBNP (O-SLBNP), which has the same static load level as S-SLBNP. Heart rate (HR), thoracic impedance (Z0), and mean arterial pressure (MAP) were measured from 11 male subjects. The transfer functions of gains from MAP to HR (Gain-HR/MAP) and from Z0 to HR (Gain-HR/Z0) were calculated as indexes of arterial baroreflex and cardiopulmonary baroreflex regulation of HR, respectively. The Gain-HR/MAP in the 180-s period (2.11 ± 0.17 bpm/mmHg; mean ± SEM) was larger than that of the 30-s period (1.04 ± 0.09 bpm/mmHg); however, there was no significant difference between the SLBNP conditions. The Gain-HR/Z0 in C-SLBNP (9.37 ± 1.47 bpm/ohm) was smaller than that of the other conditions [18.46 ± 2.45 bpm/ohm (O-SLBNP); 16.09 ± 2.29 bpm/ohm (S-SLBNP)]. Using S-SLBNP could reduce the measurement time needed to examine the arterial baroreflex. However, the cardiopulmonary baroreflex was modified by the static load of SLBNP.Ishibashi K, Oyama F, Yoshida H, Iwanaga K. Additive effects of sinusoidal lower body negative pressure on cardiovascular responses. Aerosp Med Hum Perform. 2017; 88(2):137-141.

Transient response of bilayered elastic strips with interfacial diffusion and sliding in cylindrical bending

Time-dependent deformations of bilayered elastic strips with interfacial diffusion and sliding in cylindrical bending are studied. A film–substrate system is also addressed by letting the thickness of one layer approach infinity. Our solution clearly indicates that the stresses and displacements in the strip evolve with two relaxation times when its upper surface is subjected to a sinusoidal pressure. Explicit and elementary expressions of the relaxation times are derived. The steady-state displacement jumps across the interface are found independent of the elastic property and thickness of the lower layer free of external loading. When the film is extremely thin, the relaxation times are independent of the elastic property of the substrate; when the film is extremely thick, the relaxation times are found independent of the film thickness. Detailed numerical results are presented to show the influence of the material, geometric and interface parameters on the relaxation times and on the evolving displacements and stresses in the strip or in the film–substrate system. Finally, the state-space method is proposed to determine the transient elastic field in simply supported multilayered elastic strips with interfacial diffusion and sliding under thermomechanical loads.

Liquid sinusoidal pressure measurement by laser interferometry based on the refractive index of water.

A new method with laser interferometry is used to enhance the traceability for sinusoidal pressure calibration in water. The laser vibrometer measures the dynamic pressure based on the acousto-optic effect. The relation of the refractive index of water and the optical path length with the pressure's change is built based on the Lorentz-Lorenz equation, and the conversion coefficients are tested by static calibration in situ. A device with a piezoelectric transducer and resonant pressure pipe with water is set up to generate sinusoidal pressure up to 20 kHz. With the conversion coefficients, the reference sinusoidal pressure is measured by the laser interferometer for pressure sensors' dynamic calibration. The experiment results show that under 10 kHz, the measurement results between the laser vibrometer and a piezoelectric sensor are in basic agreement and indicate that this new method and its measurement system are feasible in sinusoidal pressure calibration. Some disturbing components including small amplitude, temperature change, pressure maldistribution, and glass windows' vibration are also analyzed, especially for the dynamic calibrations above 10 kHz.

Finite volume analysis of laminated composite plates

SummaryA numerical procedure for analysis of general laminated plates under transverse load is developed utilizing the Mindlin plate theory, the finite volume discretization, and a segregated solution algorithm. The force and moment balance equations with the laminate constitutive relations are written in the form of a generic transport equation. In order to obtain discrete counterparts of the governing equations, the plate is subdivided into N control volumes by a Cartesian numerical mesh. As a result, five sets of N linear equations with N unknowns are obtained and solved using the conjugate gradient method with preconditioning.For the method validation, a number of test cases are designed to cover thick and thin laminated plates with aspect ratio (width to thickness) from 4 to 100. Simply supported orthotropic, symmetric cross‐ply, and angle‐ply laminated plates under uniform and sinusoidal pressure loads are solved, and results are compared with available analytical solutions. The shear correction factor of 5/6 is utilized throughout the procedure, which is consistent with test cases used in the reviewed literature. Comparisons of the finite volume method results for maximum deflections at the center of the plate and the Navier solutions obtained for aspect ratios 10, 20, and 100 shows a very good agreement. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Abnormal Liver Stiffness Measurement in a Patient with Waldenstrom Macroglobulinemia: Nuances in Interpreting the Findings

Background: Liver stiffness measurement (LSM) using vibration-controlled transient elastography (VCTE) provides an estimate of liver fibrosis, non-invasively, in a quick and efficient manner. Its use and interpretation of LSM is limited. In the current case, we report our findings of abnormal LSM and liver histology in a patient with Waldenstrom Macroglobulineima (WM) with evidence of portal hypertension. Case: A 84-year-old white man with history notable for WM and history of pulmonary embolism on chronic anticoagulation presented with new-onset ascites. His blood work revealed isolated elevation in alkaline phosphatase (AST 14 U/L, ALT 7 U/L, ALP 173 U/L, GGT 275 u/L and total bilirubin 0.6 mg/dL) with a platelet count was 208 k/cumm. Blood work for competing etiology was negative for viral, metabolic, and autoimmune hepatitis (negative viral hepatitides, normal iron studies, normal alpha-1-antitrypsin level, negative anti-smooth muscle antibody and negative anti-mitochondrial antibody with normal immunoglobulins (other than presence of IgM kappa monoclonal protein) ruling out primary biliary cirrhosis). Ultrasound with dopplers showed cirrhotic appearing liver, cholelithiasis, mild ascites not amenable to diagnostic paracentesis, and patent portal veins. MRCP showed normal appearing liver, mild ascites, and gallbladder sludge without biliary dilation. Evaluation with VCTE after paracentesis revealed elevated LSM at 12.2 with IQR% of 9%. Pressure measurements during transjugular liver biopsy noted normal hepatic vein pressure gradient (HVPG) of 6 mmHg (corrected sinusoidal pressure 10 mmHg (RA 1 mmHg, IVC 5 mmHg, free HV 5 mmHg, wedge 11 mmHg), consistent with pre-sinusoidal portal hypertension. Liver histology showed nodularity in the absence of significant fibrosis. Reticulin stain confirmed nodularity and showed areas of hepatic trabecular compression and others with trabecular thickening. Focal mild sinusoidal dilatation was seen. The portal tracts are largely unremarkable with patchy mild chronic inflammation and minimal ductular reaction. Congo red stain was negative as well ruling out amyloidosis. Conclusion: This case highlights the rare presentation of non-cirrhotic portal hypertension with WM and the false increase in LSM due to infiltration with M protein.

Piezoelectric type acoustic energy harvester with a tapered Helmholtz cavity for improved performance

This paper reports an improved acoustic energy harvester with a tapered Helmholtz cavity. The harvester consists of a bimorph piezoelectric composite plate and a Helmholtz resonator (HR) with a tapered cavity. The architecture, operational mechanism, fabrication, and characterization of the harvesters are described. The harvesters are tested under sinusoidal sound pressure levels (SPLs) inside a lab as well as random SPLs in a real ambient acoustical environment. When a harvester with a tapered HR and without proof mass attached to its piezoelectric plate is characterized at a sinusoidal SPL of 130 dB, a maximum power of 90.6 μW is delivered to 1 kΩ load. In comparison, a similar harvester with a cylindrical shape HR produced a maximum power of 51.4 μW under the similar acoustic conditions. It is found that 76.26% increase in power is achieved with the tapered cavity for the HR. Furthermore, due to the attachment of a proof mass (0.84 g) with the harvester, its power production capability is further increased by 103.3%, from 90.6 to 184.18 μW. Moreover, in a real environment, the maximum voltage amplitudes of about 260 and 280 mV are produced by the harvester when placed in the surrounding of a motorbike and domestic electric generator, respectively.