Acoustic Energy Research Articles

Experimental Study of Storing Electrical Energy Generated by an Acoustic Energy Harvester Into a Supercapacitor

<p class="Abstract">Acoustic energy harvester is a device used to convert environmental noise into electrical energy. Many researches on acoustic energy harvesting have been carried out, but most of them have not yet reached the stage of storing the electrical energy produced. This paper presents an experimental study of storing electrical energy generated by an acoustic energy harvester into a supercapacitor. The acoustic energy harvester in this study used a 4-inch woofer loudspeaker as a noise converter into electricity, equipped with a straight cylindrical resonator, a cylindrical housing, and an electric current rectifier unit. The supercapacitor used has a specification of 100F/2.7V. Experiments were carried out by using several variations of the sound frequency with three variations of sound pressure level (SPL) namely 90 dB, 95 dB, and 100 dB, and by measuring the supercapacitor voltage in a charging time of 60 minutes. It was found that the supercapacitor voltage reached 368 mV which was obtained from noise sound with an SPL of 100 dB and a frequency of 54 Hz which gave an initial charging electric current of about 12 mA. In the last five minutes of charging, the increase in supercapacitor voltage was still linear with time at a rate of about 5.2 mV/min. Therefore, the supercapacitor voltage can still significantly increase if the charging continues.</p>

Acoustic characterization of natural areca catechu fiber‐reinforced flexible polyurethane foam composites

AbstractThe development of acoustic absorbers from natural resources is a novel approach in acoustics. In the current study, the effect of unprocessed raw areca fiber (AF) particle reinforcement on the sound absorption (SA) behavior of polyurethane (PU) foam composites is investigated. Influences of fiber weight percentage and graded distribution of fiber with varying fiber weight percentage on the SA coefficient (SAC) of the composite foams are examined through the impedance tube approach. Morphological studies are carried out with the help of FESEM images to investigate the acoustic energy dissipation mechanism of PU foam and its composites. It is found that the SA capability of the composite foam is enhanced by increased fiber weight percentage, graded distribution of fiber wt%, varying sample thickness, and air cavity length. In general, PU‐AF composite specimens show a peak SA value of 0.95 around 450 Hz, which is not the case for other natural fiber results available in the literature. Theoretical results predicted using the JCA (Johnson‐Champoux Allard) model agree with the experimental results.

Piezoelectric system on harnessing sound energy in closed environment

Traditional energy sources are progressively moving toward depletion, resulting in a growing scarcity of energy driven by demand. In contrast, the realm of acoustic energy harvesting remains relatively unexplored, particularly within enclosed environments. In this work, we proposed a novel piezoelectric energy harvesting system, enhanced with various circuit components such as operational amplifiers and voltage quadruplers. Piezoelectric transducers are a type of electro acoustic transducer that convert the electrical charges triggered by some forms of mechanical vibrations like sound into energy. The core of the system relies on the utilization of piezoelectric technology to transform untapped sound energy into electrical energy. This innovative energy harvesting approach holds the promise of enhancing the quality of sound conditioning within enclosed spaces. Furthermore, the proposed methodology serves to mitigate the risk of noise-induced trauma, which has the potential to cause detrimental long-term effects. It is also cascade into a transformative trajectory, offering sustainable energy harvesting avenues and fostering the amelioration of soundscapes within the tapestry of confined environs. The observations made increased the efficiency of the system by 6%, and the range is increased four times. In our experiments, we obtained a higher voltage of around 12 V for a theater setup with sound levels between 70 and 90 dB, which surpasses the existing results.

Underwater soundfield visualisation using directionally constrained acoustic parameters.

This paper presents an underwater soundfield visualisation method for passive-sonar applications employing circular hydrophone arrays. The method operates by segregating the space by means of beamforming into angular sectors scanning the whole horizontal plane and then computing acoustic parameters within each sector. The information from these directionally constrained parameters is fused in order to produce spatial spectra which depict the distribution of acoustic energy over bearing. The evaluation is performed on simulated data of circular hydrophone arrays mounted on rigid cylindrical baffles. Comparisons against baseline methods of similar computational complexity suggest that, for moderate to high signal-to-noise ratio levels, the proposed method offers improved performance in terms of background noise suppression, angular resolution, and direction-of-arrival estimation accuracy. Additionally, it is demonstrated that, with the appropriate choice of sector pattern, the proposed method can, at least in some cases, achieve superior performance to the baseline methods in the presence of interferers even at low signal-to-interference ratio levels. Last, the sector-based parameter diffuseness, which is directly related to the direct-to-diffuse ratio, may be used both as a weight function to further attenuate the background noise level and as a confidence measure of the estimation accuracy.

Extraordinary transmission without resonance: Probing enhancements in acoustic transmission and energy density in hole arrays acting as a metasurface

Extraordinary transmission without resonance: Probing enhancements in acoustic transmission and energy density in hole arrays acting as a metasurface

Mechanical and Acoustic Emission Characteristics of Grouted Reinforcement in Fissure-Containing Rock-like Specimens

In order to study the reinforcing effect of the different grouting materials applied in fissure rock engineering, ultra-fine cement slurry, cement–silicate slurry, and MARITHAN® were used to carry out grouting tests on specimens of fissure-containing rocks. With the help of a uniaxial compression acoustic emission test system, the mechanical characteristics of the grouted specimens were obtained, and the damage process of the specimens was revealed by using the acoustic emission signals. The tested results showed the following: the residual strength of the grouted specimens using the three grouting materials increased by 16.931%, 13.075%, and 39.998%, respectively; the ultra-fine cement grouting and cement–silicate grouting specimens showed damage patterns of shear-slip damage along the original rupture surface; the specimens of MARITHAN® grouting cracked from a position near the end of the specimen with no damage to the grouted body portion; the cumulative acoustic emission energy curves of the grouted specimens showed obvious stage characteristics; and the acoustic emission energy distribution characteristics of the grouted specimens differed depending on the grouting materials.

A hybrid energy harvesting framework and graphene‐based supercapacitor for 6G and smart grid networks

SummaryThis paper proposes a novel hybrid energy harvesting framework integrated with a graphene‐based supercapacitor to address the energy demands of 6G communication systems and smart grid networks. To ensure consistent power generation, the proposed framework combines diverse energy harvesting mechanisms, including acoustic, vibration, and radio frequency (RF) energy sources. These harvested energies are then efficiently managed and stored in a proposed graphene‐based supercapacitor compared with existing Li‐ion batteries, due to its high energy density and rapid charge‐discharge capabilities. Smart grids and 6G networks can utilize the energy that hybrid systems harvest. This paper examines the analysis of RF energy extracted from various antenna configurations. In the acoustic energy harvesting system, energy extraction has been achieved by subjecting it to acoustic pressure and impedance. Notably, the inclusion of acoustic impedance has resulted in a greater amount of harvested energy. The vibration energy harvesting analysis with angular frequencies under various force conditions is employed. The magnitude of force applied to the harvesting system significantly influences the efficiency of the harvested energy. The three‐dimensional structure and voltage levels of the graphene‐based supercapacitor have been examined for various electrodes. For maximizing the harvested hybrid energy, convex optimization is formulated due to its ability to efficiently navigate complex design spaces while ensuring reliable and globally optimal solutions. CVX tool in MATLAB is used for validation. The results improve the energy harvesting efficiency and enhance the power availability of all the harvesting sources. Furthermore, the compatibility of the proposed framework with existing network infrastructure highlights its potential for seamless integration into real‐world communication and energy distribution systems.

Delta EC Simulation on Influence of Resonator Length in Close-Open Standing Wave Thermoacoustic Engine

<p class="Abstract"><em><span lang="EN-US">Many applications of thermoacoustic engines in engineering. With its pressure of it, the energy can be harvested and can be converted to many other needs of energies like electrical energy. Energy in thermal form is converted to become acoustic energy and subsequently used to activate a bidirectional turbine. The resonator is very influential toward the power of the thermoacoustic engines. Simulation study with Delta EC fit to make predictions acoustic power as representative performance in thermoacoustic engine with close-open type and standing wave of oscillation. In this study, the material of the resonator is made from a stainless-steel duct with a diameter size of 50.8 mm with three variations of the length. The Standing-Wave Thermoacoustic Engine (SWTE) generates acoustic energy from a temperature gradient of 315 – 993 K. </span></em><em><span lang="IN">In this simulation, Acoustic Power decreased when the resonator length was extended. The shortest resonator had an acoustic power of 50.4 W, and the longest resonator had an acoustic power of 35.7 W.</span></em></p>

Nonconventional Tether Structure for Quality Factor Enhancement of Thin-Film-Piezoelectric-on-Si MEMS Resonator.

This article presents a new design of supporting tethers through the concept of force distribution. The transmitted force applied on tethers will be distributed on the new tether design area, resulting in low acoustic energy transferred to anchor boundaries and stored energy enhancement. This technique achieves an anchor quality factor of 175,000 compared to 58,000 obtained from the conventional tether design, representing a three-fold enhancement. Furthermore, the unloaded quality factor of the proposed design improved from 23,750 to 27,442, representing a 1.2-fold improvement.

Fracture energy evolution and fractal characteristics of shales with different quartz contents

Quartz is an important mineral component of shale. In order to explore the influence of quartz content on the mechanical properties of shale, this article conducted numerical simulation of the Lower Cambrian Niutitang Formation shale in Fenggang Block 3, Guizhou using RFPA software. The results show that the effect of quartz content on compressive strength is more significant than that on elastic modulus. The damage modes of shale with different quartz content are presented as 5 types, namely, oblique tension damage (21%, 27%), inverted N-shaped damage (33%), V-shaped damage (39%), inverted V-shaped damage (45%), and λ-shaped damage (51%). When the content of quartz is higher than a certain value, the microscopic damage of shale tends to be more complicated. The destruction acoustic emission energy and fractal dimension show significant difference with quartz content. The research results of this article will play a certain role in promoting shale gas exploitation. Highlights The influence of quartz content on the mechanical properties of shale is numerically simulated. The energy evolution law of shale destruction in the presence of quartz is analyzed. The complexity of shale destruction caused by quartz content is analyzed. It is proven by a similarity test that shale changes with different mechanical properties of quartz content.

Supramolecular dissipative self‐assembly systems: Approaches and applications

AbstractDissipative self‐assembly (DSA) system requires a continuous supply of fuels to maintain the far‐from‐equilibrium assembled state. Living organisms exist and operate far from the thermodynamic equilibrium by continuous consumption of energy taken from the surroundings, so how to realize the construction of the artificial DSA system has attracted much attention by researchers all over the world. Owing to dynamic controllable noncovalent interactions, artificial supramolecular DSA systems have achieved higher functions fueled by various types of energy, such as chemical fuels, light, electric energy, acoustic energy, and mechanical energy. Upon the input of external fuels, nonactive precursors can be activated to form building blocks at higher energy levels and then self‐assemble into transient supramolecular structures. As the proceeding of deactivation reaction, the building blocks with higher energy level dissipate back to the initial precursors, resulting in the disassembly process, to complete a full cycle. In this review, we summarize the recent advances of artificial supramolecular DSA systems on its construction strategies and energy‐fueled regulation approaches. The applications of supramolecular DSA systems in luminescence modulating, information encryption, self‐regulating gels, drug delivery, and catalysis are also discussed. We hope that this review article will facilitate further understanding and development of DSA systems.

Response of sound propagation characteristics to Luzon cold eddy coupled with tide in the Northern South China Sea

The northern part of the South China Sea is a complex ocean environment with a large range of tidal waves and the stable Luzon cold eddy, which significantly influence the sound propagation characteristics through their impact on sound speed. This study uses a 3D ocean-acoustic framework consisting of MITgcm and BELLHOP ray model to investigate the coupled effects of the Luzon cold eddy and tidal waves. Firstly, the model incorporates tidal assimilation to reconstruct the hydrographic field and compute the sound speed field. Subsequently, the sound propagation in a representative region in the northern South China Sea is simulated to compare the response of sound propagation characteristics to the Luzon cold eddy only, tide only, and the coupled effect of both. The results demonstrate that the cold eddy shifts the location of the convergence zone forward by over 5 km at most. Further, it also makes the acoustic energy focus on the first few arrivals and delays the arrival time of rays by about 0.1 s. The tidal waves intensify these effects, resulting in a further increase of the forward distance of the convergence zone by 2-5 km and a delay in arrival time by 0.02 s. Sound propagation in the coupled influence of these two dynamic processes is exposed to steady perturbations from the cold eddy and spatial-temporal perturbations from tidal waves. The model in this study provides valuable insight for underwater detection and positioning in the realistic ocean environment.

Real-Time Acoustic Simulation Framework for tFUS: A Feasibility Study Using Navigation System

Transcranial focused ultrasound (tFUS), in which acoustic energy is focused on a small region in the brain through the skull, is a non-invasive therapeutic method with high spatial resolution and depth penetration. Image-guided navigation has been widely utilized to visualize the location of acoustic focus in the cranial cavity. However, this system is often inaccurate because of the significant aberrations caused by the skull. Therefore, acoustic simulations using a numerical solver have been widely adopted to compensate for this inaccuracy. Although the simulation can predict the intracranial acoustic pressure field, real-time application during tFUS treatment is almost impossible due to the high computational cost. In this study, we propose a neural network-based real-time acoustic simulation framework and test its feasibility by implementing a simulation-guided navigation (SGN) system. Real-time acoustic simulation is performed using a 3D conditional generative adversarial network (3D-cGAN) model featuring residual blocks and multiple loss functions. This network was trained by the conventional numerical acoustic simulation program (i.e., k-Wave). The SGN system is then implemented by integrating real-time acoustic simulation with a conventional image-guided navigation system. The proposed system can provide simulation results with a frame rate of 5 Hz (i.e., about 0.2 s), including all processing times. In numerical validation (3D-cGAN vs. k-Wave), the average peak intracranial pressure error was 6.8 ± 5.5%, and the average acoustic focus position error was 5.3 ± 7.7 mm. In experimental validation using a skull phantom (3D-cGAN vs. actual measurement), the average peak intracranial pressure error was 4.5%, and the average acoustic focus position error was 6.6 mm. These results demonstrate that the SGN system can predict the intracranial acoustic field according to transducer placement in real-time.

Identification by inelastic X-ray scattering of bulk alteration of solid dynamics due to liquid wetting

We examine the influence at room temperature of the deposit of a water layer on the phonon dynamics of a solid. It is shown that the water wetting at the surface of an Alumina monocrystal has deep effects on acoustic phonons, propagating over several hundred µm distance and taking place on a relatively long time scale. The effect of the wetting at the boundary is two-fold: a hardening of both transverse and longitudinal acoustic phonons is observed as well as a relaxation of internal stresses. These acoustic phonon energy changes were observed by inelastic X-ray scattering up to 40 meV energy loss, allowing us to probe the solid at different depths from the surface.

Mechanical damage characteristics and acoustic emission characteristics of a bolt-slurry interface under cyclic pull-out loading

To consider the effects of various mining stresses in an actual project, a comprehensive laboratory pull-out study of the bolting system under different cyclic loads was carried out, a high stiffness MTS815.04 rock mechanics test system and an independently designed indirect pullout test device and an acoustic emission system was used for synchronous monitoring. Damage failure mechanism of bolt-slurry interface under cyclic loading revealed from macroscopic strength and deformation characteristics and microscopic damage in depth. The results are as follows.: (1) Compared with static pull-out loading, the bolting system under cyclic loading will enter the damage failure state earlier. (2) The greater the cyclic loading and unloading rate are, the greater the impact on the bolt-slurry interface, and the easier it is for sudden macroscopic damage to occur. (3) The greater the cyclic load stress amplitude is, the stronger the acoustic emission activity of the bolt-slurry interface, the greater the damage to the bolt-slurry interface, and the easier it is to fail and de-bond. (4) Finally, the acoustic emission energy, energy rate and count can be used to evaluate the damage characteristics of the anchor interface during cyclic drawing, and the analysis results are in good agreement with the macroscopic damage results. The research results can provide a reference for the support design and performance monitoring of full-length anchor bolts under different cyclic loads.

Matrix effect suppressing in the element analysis of soils by laser-induced breakdown spectroscopy with acoustic correction

Laser-induced breakdown spectroscopy (LIBS) has been used for soil analysis, but its measurement accuracy is often influenced by matrix effects of different kinds of soils. In this work, a method for matrix effect suppressing was developed using laser-induced plasma acoustic signals to correct the original spectrum, thereby improving the analysis accuracy of the soil elements. A good linear relationship was investigated firstly between the original spectral intensity and the acoustic signals. The relative standard deviations (RSDs) of Mg, Ca, Sr, and Ba elements were then calculated for both the original spectrum and the spectrum with the acoustic correction, and the RSDs were significantly reduced with the acoustic correction. Finally, calibration curves of Mg I 285.213 nm, Ca I 422.673 nm, Sr I 460.733 nm and Ba II 455.403 nm were established to assess the analytical performance of the proposed acoustic correction method. The values of the determination coefficient (R 2) of the calibration curves for Mg, Ca, Sr, and Ba elements, corrected by the acoustic amplitude, are improved from 0.9845, 0.9588, 0.6165, and 0.6490 to 0.9876, 0.9677, 0.8768, and 0.8209, respectively. The values of R 2 of the calibration curves corrected by the acoustic energy are further improved to 0.9917, 0.9827, 0.8835, and 0.8694, respectively. These results suggest that the matrix effect of LIBS on soils can be clearly improved by using acoustic correction, and acoustic energy correction works more efficiently than acoustic amplitude correction. This work provides a simple and efficient method for correcting matrix effects in the element analysis of soils by acoustic signals.

Analysis of Influencing Factors for Stackable and Expandable Acoustic Metamaterial with Multiple Tortuous Channels.

To reduce the noise generated by large mechanical equipment, a stackable and expandable acoustic metamaterial with multiple tortuous channels (SEAM-MTCs) was developed in this study. The proposed SEAM-MTCs consisted of odd panels, even panels, chambers, and a final closing plate, and these component parts could be fabricated separately and then assembled. The influencing factors, including the number of layers N, the thickness of panel t0, the size of square aperture a, and the depth of chamber T0 were investigated using acoustic finite element simulation. The sound absorption mechanism was exhibited by the distributions of the total acoustic energy density at the resonance frequencies. The number of resonance frequencies increased from 13 to 31 with the number of layers N increasing from 2 to 6, and the average sound absorption coefficients in [200 Hz, 6000 Hz] was improved from 0.5169 to 0.6160. The experimental validation of actual sound absorption coefficients in [200 Hz, 1600 Hz] showed excellent consistency with simulation data, which proved the accuracy of the finite element simulation model and the reliability of the analysis of influencing factors. The proposed SEAM-MTCs has great potential in the field of equipment noise reduction.

Increased intracellular diffusivity of macromolecules within a mammalian cell by low-intensity pulsed ultrasound

Whilst a number of studies have demonstrated that low-intensity pulsed ultrasound (LIPUS) is a promising therapeutic ultrasound technique that can be used for delivering mild mechanical stimuli to target tissue non-invasively, the underlying biophysical mechanisms still remain unclear. Most mechanism studies have focused explicitly on the effects of LIPUS on the cell membrane and mechanosensitive receptors. In the present study, we propose an additional mechanism by which LIPUS propagation through living cells may directly impact intracellular dynamics, particularly the diffusion transport of biomolecules. To support our hypothesis, human epithelial-like cells (SaOS-2 and HeLa) seeded on a confocal dish placed on a microscope stage were exposed to LIPUS with various exposure conditions (ultrasound frequencies of 0.5, 1 and 3 MHz, peak acoustic pressure of 200 and 400 kPa, a pulse repetition frequency of 1 kHz and a 20 % duty cycle), and the diffusivities of various sizes of biomolecules in the cytoplasm area were measured using fluorescence recovery after photobleaching (FRAP). Furthermore, giant unilamellar vesicles (GUVs) filled with macromolecules were used to examine the physical causal relationship between LIPUS and molecular diffusion changes. Nucleocytoplasmic transport coefficients were also measured by modified FRAP that bleaches the whole cell nuclear region. Extracellular signal-regulated kinases (ERK) activity (the phosphorylation dynamics) was monitored using fluorescence resonance energy transfer (FRET) microscopy. All the measurements were taken during, before and after the LIPUS exposure. Our experimental results clearly showed that the diffusion coefficients of macromolecules within the cell increased with acoustic pressure by 12.1 to 33.5 % during the sonication, and the increments were proportional to their molecular sizes regardless of the ultrasound frequency used. This observation in living cells was consistent with the GUVs exposed to the LIPUS, which indicated that the diffusivity increase was a passive physical response to the acoustic energy of LIPUS. Under the 1 MHz LIPUS exposure with 400 kPa, the passive nucleocytoplasmic transport of enhanced green fluorescent protein (EGFP) was accelerated by 21.4 %. With the same LIPUS exposure condition, both the diffusivity and phosphorylation of ERK induced by EGF treatment were significantly elevated simultaneously, which implied that LIPUS could also modify the kinase kinetics in the signal transduction process. Taken together, this study is the first attempt to uncover the physical link between LIPUS and the dynamics of intracellular macromolecules and related biological processes that LIPUS can possibly increase the diffusivity of intracellular macromolecules, leading to the changes in the basic cellular processes: passive nucleocytoplasmic transport and ERK. Our findings can provide a novel perspective that the mechanotransduction process that the intracellular region, in addition to the cell membrane, can convert the acoustic stimuli of LIPUS to biochemical signals.

Heat Transfer Analysis in Sound-Enhanced Fluidized Beds Containing Geldart B-C Binary Mixtures

An experimental study was carried out on the binary mixing behaviour of Group C with Group B particles as well as the heat transfer behaviour between the bed and submerged heating tube in an acoustic field. The effects of excessive air velocity, sound pressure intensity, and local and averaged heat transfer coefficient were studied for five binary mixes. Different binary mixture fluidization ratios with and without sound aid are used to compare the results. The study also discusses the measurement techniques used, including pressure measurements and the characteristics of the bed solids. Sand and hydrophilic bituminous coal are used as the binary mixture materials, with different proportions of each. The experiments are conducted both with and without acoustic assistance to compare the outcomes. This study provides insights into the heat transfer behavior and binary mixing in a sound-assisted fluidized bed. The findings indicate that sound assistance has a significant impact on the heat transfer performance of Geldart B-C binary mixtures in fluidized beds. It highlights the potential benefits of using acoustic energy to improve fluidization quality in binary systems.

Acoustic resonance therapy is safe and effective for the treatment of nasal congestion in rhinitis: A randomized sham-controlled trial.

Acoustic resonance therapy (ART) is a novel vibrational treatment that delivers patient-specific resonant frequency acoustic energy to the sinonasal cavities. In a pilot study, ART was effective for the acute treatment of nasal congestion. We conducted a sham-controlled randomized trial to validate the efficacy of ART when administered daily for 2weeks. A total of 52 adult patients were enrolled in a multi-center, randomized, double-blinded, sham-controlled, interventional study evaluating ART administered by a vibrational headband. Patients received either active treatment or a non-therapeutic sham treatment twice daily over 2weeks. Clinical endpoints were the average change in nasal congestion sub-score of the Total Nasal Symptom Score (TNSS) and the average change in composite TNSS. ART resulted in a significantly greater mean change in the nasal congestion sub-score compared to sham (-0.87 [95% confidence interval [CI] -1.11, -0.62] vs. -0.44 [95% CI -0.64, -0.23], p=0.008). ART also resulted in a significantly greater reduction in the composite TNSS versus sham, (-2.85 [95% CI -3.85, -1.85], vs. -1.32 [95% CI -2.27, -0.36], p=0.027). The response rate, determined by a nasal congestion sub-score minimal clinically important difference of 0.23, was 80.8% for ART and 46.2% for sham, with an adjusted risk ratio of 1.95 (95% CI 1.26, 3.02, p=0.003) in favor of ART. Safety endpoints showed no adverse events. ART is a safe and effective non-pharmacologic alternative for the treatment of nasal congestion.