Acoustic Power Levels Research Articles

Weighted ultrasound entropy imaging for HIFU ablation monitoring with improved sensitivity and contrast.

Although B-mode imaging has been widely used in ultrasound-guided high-intensity focused ultrasound (HIFU) treatment, challenges remain in improving its quality and sensitivity for monitoring the thermal dose. Recently, quantitative ultrasound (QUS) imaging has been recognized with the potential to better sense the changes in the microstructure of ablated tissues. This study proposed to use a QUS method called weighted ultrasound entropy (WUE) imaging to monitor the HIFU ablation. Based on ex-vivo and in-vivo experiments, WUE images reflecting tissue changes during HIFU treatment under different acoustic power levels (174-308W) were reconstructed with a newly established imaging framework. The performance of the proposed WUE imaging in the monitoring of HIFU treatment was compared with the corresponding B-mode images in terms of their contrast-to-noise ratios (CNRs) between the focal region and the background. It was found that HIFU irradiation with higher power generated larger WUE values in the focal region, and the bright spots grew in size as the acoustic sonication proceeded. Compared with the in-situ B-mode images, the WUE images had higher image quality in indicating lesion formation, with a 39.2%-53.4% improvement in the CNR at different stages. Meanwhile, a correlation (R=0.84) between the damage area estimated in WUE images and that measured from the dissected ex-vivo tissue samples was found. WUE imaging is more sensitive and accurate than B-mode imaging in monitoring HIFU therapy. These findings suggest that WUE imaging could be a promising technique for assisting ultrasound-guided HIFU ablation.

Numerical Aerodynamic and Aeroacoustic Analysis of Toroidal Propeller Designs

Drones have a major drawback which prevents them from being used extensively - the excessive noise they produce. This article presents an optimization process of aerodynamic noise reduction for a novel design called the Toroidal Propeller, which consists of two blades looping joined in a manner where the end of one blade arches back into the other, has been designed by the Aerospace Propulsion Systems (APSs) research team at School of Mechanical Engineering, Hanoi University of Science and Technology. In addition, four toroidal propellers with different curved shapes (pitch) and Number of Blades (NOB) are considered. The goal of this research is to evaluate the effects of modifying the geometry design of the Toroidal Propeller on the intensity of blade tip vortex and aerodynamic flow characteristics passing through the blade. The ultimate goal is to decrease blade tip vortex and turbulence produced by the blade, which can help estimate the sound pressure level and minimize it without causing significant performance losses. Based on the outcome results, the models of the four geometry studies are compared in terms of Acoustic Power Level (APL), Surface Acoustic Power Level (SAPL), Thrust, Torque, and Power. In general, the propeller model with NOB of 3 provides the most optimal efficiency in terms of both Thrust and APL. At the output cross-section, the APL dropped from nearly 139 dB to 121 dB, while thrust increased from almost 6.2N to 8.7N compared to the first version of the Toroidal Propeller model.

Study of hydraulic turbine flow-induced noise distribution law based on defective runner blade

Abstract In order to analyse flow-induced noise distribution law under the defective runner blade, this paper performs defective treatment on the runner blade according to the HLA855a-LJ-250 hydraulic turbine model. Two kinds of blade models, intact blade and outlet side abrasive blade, are established respectively, and the Realizable k-ε turbulence model and broadband noise source model are used to simulate the hydraulic turbine under rated operating conditions. The simulation results show: 1)Double-row leaf grilles and runner blade are the main dipole flow-induced noise sources; 2)Significant differences in the distribution of the acoustic power levels of the double-row leaf grilles’ characteristic blades and the runners’ characteristic blades under different Schemes; 3)Runner defective blades have less effect on the acoustic power level of spiral case, the rest of the overflow components acoustic power level has a tendency to increase, especially the runner has the greatest impact. The maximum increase in acoustic power level of the runner is almost 17 dB, followed by double-row leaf grilles with an increase of around 8 dB. Therefore, critical attention needs to be paid to the abnormal noise signals of runner and double-row leaf grilles.

Effects of an Owl Airfoil on the Aeroacoustics of a Small Wind Turbine

Aerodynamic noise emitted by small wind turbines is a concern due to their proximity to urban environments. Broadband airfoil self-noise has been found to be the major source, and several studies have discussed techniques to reduce airfoil leading-edge and trailing-edge noises. Reduction mechanisms inspired by owl wings and their airfoil sections were found to be most effective. However, their effect/s on the tip vortex noise remain underexplored. Therefore, this paper investigates the effects of implementing an owl airfoil design on the tip vortex noise generated by the National Renewable Energy Laboratory (NREL) Phase VI wind turbine to gain an understanding of the relationship, if any, between airfoil design and the tip vortex noise mechanism. Numerical prediction of aeroacoustics is employed using the Ansys Fluent Broadband Noise Sources function for airfoil self-noise radiation. Detailed comparisons and evaluations of the generated acoustic power levels (APLs) for two distinguished inlet velocities were made with no loss in torque. Although the owl airfoil design increased the maximum generated APL by the baseline model from 105 dB to 110 dB at the lower inlet velocity, it significantly reduced the surface area generating the noise, and reduced the maximum APL generated by the baseline model by 4 dB as the inlet velocity increased. The ability of the owl airfoil to mitigate the velocity effects along the span of the blade was found to be its main noise reduction mechanism.

Transducer module apodization for reducing bone heating during focused ultrasound uterine fibroid ablation

During MR-guided focused ultrasound (MRgFUS) for uterine fibroids, thermoablation of tissue near spine/hips is challenging due to bone heating that can cause patient pain and potentially damage nerves. Here we investigate transducer module apodization for maximizing the focal-to-bone heating ratio (ΔT ;ratio) in silico using a 6144-element flat fully populated phased array operating at 0.5 MHz (Arrayus Technologies, Inc.). Acoustic and thermal simulations were performed using anatomies of ten patients who underwent MRgFUS ablation for uterine fibroids with this device as part of a clinical trial (NCT03323905). Transducer modules (64 elements/module) whose beams intersected no-pass regions were identified, their amplitudes were reduced by varying blocking percentage levels, and the resulting temperature field distributions were evaluated across multiple sonications per patient. For all simulated sonications transducer module blocking improved ΔT ;ratio compared to no blocking. In 42% of sonications, full module blocking maximized ΔT ;ratio, with mean improvements of 97% ± 55% and 47% ± 36% in hip and spine compared to no blocking, at the cost of increased focal thermal volumes and acoustic power levels. In the remaining sonications, partial module blocking provided increased ΔT ;ratio values (39% ± 45% in hip, 19% ± 15% in spine targets) relative to full blocking. The optimal blocking percentage varied depending on the specific treatment geometry.

Aeroacoustic assessment of a rectilinear cascade with leading edge serrations: predictions and measurements

This study aims at evaluating previously designed leading edge serrations for the turbulence-cascade interaction noise reduction on a rectilinear cascade. Low and high-fidelity methodologies have been investigated and are compared to experimental data issued from a cascade test rig mounted in an anechoic wind tunnel. These methods include mean flow simulations for aerodynamic performance analysis, analytical models well suited to acoustic design, an Euler-based numerical method coupled with an integral method for the far-field acoustic prediction, and finally high-fidelity simulations based on the lattice Boltzmann method to take account for installation effects. The scopes and benefits of each methodology are discussed. Fast design methods and mid-fidelity numerical simulations provide satisfactory trends, but only high-fidelity simulations are able to accurately match acoustic spectra and sound power level reductions measured by microphone antenna.

Production noise on an automated molding line in a foundry

The purpose of the work is to determine the nature of the noise generated during the operation of manual pneumatic rammers, an automated molding line and knockout grids in the foundry shop based on determining the levels of acoustic noise parameters in the mold manufacturing area and ways to reduce their level. To determine the noise parameters, a mode noise spectrum analyzer SL-5868F was used with subsequent digitization of the data obtained on the analyzer. Measurements of noise parameters were carried out at the site for the production of foundry molds with manual pneumatic rammers and an automatic molding line, as well as at the site for knocking out castings on knockout grids. It has been established that the noise generated in the areas of molding and knocking out molds, regardless of the molding method (manual, automatic) and the model of the knockout grid used, is broadband, and there is no homogeneity in the sound field of the generated noise, which is due to the generation of noise from sources characterized by differences in acoustic power levels and the nature of the noise spectrum. The noise from equipment or a technological operation with a shock nature is not constant and has a maximum sound power level in the region of medium and high frequencies generated by the equipment under study. It is possible to reduce the noise level in the foundry shop analyzed in the work by implementing a set of measures to modernize the molding and knocking out equipment or introducing into production an alternative method of manufacturing and knocking out foundry molds, in which, if it is possible to produce castings of a given nomenclature in the required volume with the required level of quality, the above mentioned are excluded and other sources of noise generation of unacceptable levels.

Study on the Vibration and Sound Radiation Performance of Micro-Perforated Laminated Cylindrical Shells

In response to the problem of vibration and noise reduction in equipment with cylindrical shell structures, this paper focuses on the micro-perforated laminated cylindrical shell structure and establishes its finite element model. Through comparative analysis with experimental results, the reliability of the finite element modeling method is verified. Based on this, the paper places particular emphasis on the vibration and acoustic radiation performance of the structure in the 1–1000 Hz frequency range under free conditions to understand the impact of different laminated shell structures, micro-perforation parameters (porosity, aperture), sound-absorbing foam materials, and placement methods. The results indicate that micro-perforated structures can efficiently reduce the structural radiated sound power level at specific frequencies, but the overall reduction in radiated sound power level is not significant. Various types of foam are effective in reducing the structural radiation acoustic power level, with polyurethane performing best among them. Changing the location of foam placement has a relatively insignificant impact on the structural radiation acoustic power level.

Effect of the Same Sized Holes with Different Geometries and Angles in the Gun Silencer Diffusers on the Acoustic Power Level

The bullet, which is activated by the firing of the gunpowder in the gun silencer, comes out of the gun's barrel. In the meantime, an irritating muzzle blast sound is heard that lasts for a few milliseconds. With this explosion, acoustic sound waves are formed that are independent of the bullet's path of motion. In this study, a silencer that can be attached to a low-power 9 mm firearm is modeled. Afterward, the impact of holes with the same area drilled in different geometries and angles on the diffusers (compartments) of the silencer are compared. The Computational Fluid Dynamics (CFD) analysis method is used for this comparison. In addition, the dynamic mesh model is used where the ballistic field changes over time. This mesh model is analyzed for imperforate, circular-holed, square-holed, and triangular-holed profiles with the same area. Depending on the analyses, the pressure, velocity, and dB results obtained for the silencer outlet area are compared with each other.

Numerical Study of Comparison of Thrust Bearing Slip - No Slip Condition on Acoustic Performance

The acoustic power level (APL) produced by a thrust bearing during operation has a major effect on its performance. Therefore, this research aimed to investigate the impact of slip engineered on the noise generated by thrust bearings. A numerical approach was used to simulate open pocket bearings with varying film thickness depths. At the initial location of the slip area, three bearing models were analyzed: pocket slip, pocket no slip, and smooth slip. The results show that implementing slip can reduce noise levels, turbulence kinetic energy (TKE), and turbulence eddy dissipation (TED) rate. The average APL, TKE, and TED values were the lowest at the high film thickness

Sonochemical formation of peroxynitrite in water: Impact of ultrasonic frequency and power

There is a lack of literature on peroxynitrite formation due to sonolysis of aerated water. In this work, the impact of sonication parameters, frequency and power, on ultrasonic peroxynitrite production in aerated alkaline water was investigated. Peroxynitrite formation was clearly established with undeniable evidence at all the tested frequencies in the range of 516–1140 kHz with a typical G-value (energy-specific yield) of 0.777 × 10−10, 0.627 × 10−10, 0.425 × 10−10 and 0.194 × 10−10 mol/J at 516, 558, 860 and 1140 kHz, respectively. The ultrasonication frequency has a direct impact on the sonochemical peroxynitrite production. Increasing the ultrasonication frequency in the interval 321–1140 kHz reduces peroxynitrite formation. The most practical sonochemistry dosimetries, including hydrogen peroxide production, triiodide dosimetry, Fricke dosimetry, and 4-nitrocatechol formation, were compared with the sonochemical efficiency of the reactors used to produce peroxynitrite. The G-value, energy specific yield, for the tested dosimetries was higher than that for peroxynitrite formation, regardless of frequency. For all chemical dosimetries investigated, the same trend of frequency dependence was found as for peroxynitrite generation. The influence of ultrasonication power on peroxynitrite formation by sonication at diverse frequencies in the interval 585–1140 kHz was studied. No peroxynitrite was formed at lower acoustic power levels, regardless of frequency. As the frequency increases, more power is required for peroxynitrite formation. The production of peroxynitrite increased as the acoustic power increased, despite the frequency of ultrasonic waves. Ultrasonic power is a key factor in the production of peroxynitrite by sonolysis. Since peroxynitrite is uniformly distributed in the bulk solution, peroxynitrite-sensitive solutes can be transformed both in the bulk of the solution and in the surfacial region (shell) of the cavitation bubble. The formation of peroxynitrite should be taken into account in sonochemistry, especially at higher pH values. Ultrasonic peroxynitrite formation in alkaline solution (pH 12) can be considered as a kind of chemical dosimetry in sonochemistry.

VIBROACOUSTIC SOUNDPROOFING FOR HELICOPTER INTERIOR

As VIP passengers generally want to fly civil and executive jets where vibratory and acoustic environment is smoother than on the normal jets. Helicopter interior noise is generated by main and tail rotors, engines, main gearbox, and aerodynamic turbulence (Lu et al., 2018). Because of these sources, the tonal and broadband noise is incredibly high and needs to be reduced. Conventional passive system (soundproofing) is the best way to control the acoustic of the cabin whereas active systems (active vibration and noise control) are not completely reliable or applicable. The design of the soundproofing may be researched by simulation using one of these programs: ANSYS, SOLIDWORKS 2020 and ACOUSTIC analysis Vibroacoustic Monitoring (VAM) approach. The analyses were performed from frequency ranges, 5-10Hz and 0-2000Hz then transformed into frequency velocity domain using Proudman’s equations (Lu et al., 2017). Soundproofed ANSYS models are validated using instantaneous sound pressure levels measured within the helicopter during flight. The acoustic detection method for GAZELLE is also performed successfully in SOLIDWORKS for aluminum alloy and titanium alloy, this proves the relationship between acoustic power levels and material configuration. The noise coefficient responses of interior materials are used as main index for soundproofing helicopter interiors. The results of this research can be used for implementation of VAM approach for soundproofing helicopter interiors.

DETERMINATION OF THE ACOUSTIC POWER LEVEL EMITTED BY A MACHINE COMPONENT BY MEASURING VIBRATION

The article applies a methodology for determining the acoustic power of air-borne sound which is generated by the vibration of machinery components or the machine itself. The calculation of the acoustic power level is realized by measuring the vibration acceleration and integrating it to the vibration velocity of the rigid surface of the machinery or its component. The methodology is verified when determining the acoustic power level of operated spinning headstocks on a test facility. Undesirable noise emissions of spinning headstock bearings, as well as their operating condition, can be monitored by measuring kinematic parameters, measuring vibration acceleration and its subsequent integration. The vibration velocity was used to determine the A-weighted level and Z-weighted level of the acoustic power and at the same time to evaluate the operating condition of the two selected spinning units. The article also evaluates the importance of the correct choice of the measuring point of the analyzed spinning headstock on the test equipment when determining the level of acoustic power, which has a decisive influence on the uncertainty of the measurement.

Computational analysis on flow induced stress and acoustic vibration in a proposed silencer design for a three-cylinder in-line four-stroke spark ignition engine

Computational analysis of flowing exhaust gases inside a non-perforated silencer chamber of a commercially available three-cylinder inline four-stroke spark-ignition engine and in a modified perforated design was conducted and their respective levels of performance were predicted. Study on the existing and proposed silencer designs was carried out by way of computational fluid dynamics (CFD) analysis, structural analysis and modal analysis. Modal analysis has been performed in order to compute up to six fundamental frequencies on the aforementioned structure for analysing the response spectra for obtaining the natural frequencies at different modes of excitation. A reduction of 23.8% and 23.6% in the maximum values of static pressure and total pressure, respectively, has been observed for the proposed perforated model against the existing non-perforated silencer. The maximum acoustic power level and the maximum surface acoustic power level were found to be 9.5% and 7.3% respectively, less for the proposed design.

An in vitro Model for Experimental Evaluation of Sonothrombolysis under Tissue-mimicking Material Conditions.

The mechanical properties of therapeutic ultrasound (US) have attracted scientific interest for thrombolysis enhancement in combination with thrombolytic agents and microbubbles (MBs). The aim of the study was to develop an in vitro model to observe how the effects of sonothrombolysis change in the case where a tissue-mimicking material (TMM) is placed in the path of the US beam before the clot. Fully retracted blood clots were prepared and pulse sonicated for 1 h under various conditions. The system was in a state of real circulating flow with a branch of an open bypass and an occluded tube containing a blood clot, thus mimicking the case of ischemic stroke. The effectiveness of thrombolysis was quantified in milligrams of clots removed. An agar-based TMM was developed around the occluded tube. The clot breakdown in a TMM was found to be more pronounced than in water, presumably due to the retention of the acoustic field. A higher level of acoustic power was required to initiate clot lysis (>76 W acoustic power) using only focused US (FUS). The greatest thrombolysis enhancement was observed with the largest chosen pulse duration (PD) and the use of MBs (150 mg clot mass lysis). The synergistic effect of FUS in combination with MBs on the enzymatic fibrinolysis enhanced thrombolysis efficacy by 260% compared to thrombolysis induced using only FUS. A reduction in the degree of clot lysis was detected due to the attenuation factor of the intervening material (30 mg at 1 and 4 ms PD). In vitro thrombolytic models including a TMM can provide a more realistic evaluation of new thrombolytic protocols. However, higher acoustic power should be considered to compensate for the attenuation factor. The rate of clot lysis is slow and the clinical use of this method will be challenging.

Aerodynamic Analysis on Noise Generated from Automotive Side Mirror Using CFD

The geometry of the car's side mirror influences the aerodynamic noise. This study will use computational fluid dynamics (CFD) to investigate the effect of aerodynamic analysis on noise from the side mirror. In this study, we will design two types of side mirrors using the Honda Civic EG9 for sedans and the Range Rover Evoque for SUVs. SolidWorks software was used for geometry modelling and the analysis was completed using the ANSYS software. Three streamline velocity values (80 km/h,100km/h, 120 km/h) were chosen as references. The results of the analysis included the side mirror's drag force, acoustic contour, and velocity streamlines. Design 1, produces a maximum acoustic power level of 77.21 dB when travelling at a high speed of 120 km/h. The maximum acoustic power level for Design 2, which travels at 120 km/h is 75.71dB. In summary, Design 2's side mirror has a higher acoustic power level than Design 1's side mirror. Design 1 produces a drag force of 4.52 N at a high speed of 120 km/h while Design 2 results in a drag force of 6.36 N at a high speed of 120 km/h.

Lead-Free HIFU Transducers.

High-intensity focused ultrasound transducers operating at 4 MHz based on lead-free piezoceramics from the sodium bismuth titanate (NBT) family are described. First, the piezoelectric material (Pz12X) is evaluated from the standpoint of transducer design and its important characteristics, including temperature dependance of several parameters such as dielectric and mechanical coefficients. Then, the performance of six transducers of the same design is evaluated in terms of electro-acoustic efficiency and its dependency on the operating acoustic power level up to 30 W. Overall, the initial electro-acoustic efficiency of three independent transducers is approximately 50% at low acoustic power levels and slightly drops down to 42% as the input electric power reaches 10 W. This process is stable and fully reversible. Moreover, the stability of electro-acoustic efficiency over extended power burst cycling is studied using another two transducers up to 95×103 power bursts of 250-ms duration and acoustic power of 10 W. This protocol is beyond the typical clinical use of similar devices in practice. No significant changes in electro-acoustic performance are noted. Additionally, the input electric power and the output acoustic power, together with the temperature of the piezoelectric component, are evaluated simultaneously over the period of one power burst. It is found that the maximum operating temperature over a high-input electric power burst of 600 J is below 60°C, which defines the operational limit for such devices, as the de-poling temperature of the lead-free material is around 85°C. It is found that the lead-free material from the NBT family is also a promising alternative to lead-based PZT-type materials in high-power therapeutic ultrasound.

Cavitation Feedback Control of Focused Ultrasound Blood-Brain Barrier Opening for Drug Delivery in Patients with Parkinson's Disease.

Magnetic resonance-guided focused ultrasound (MRgFUS), in conjunction with circulating microbubbles, is an emerging technology that can transiently enhance the permeability of the blood-brain barrier (BBB) locally and non-invasively to facilitate targeted drug delivery to the brain. In this clinical trial, the feasibility and safety of BBB modulation in the putamen were evaluated for biweekly therapeutic agent delivery in patients with Parkinson's disease. The performance of the clinical MRgFUS system's cavitation feedback controller for active power modulation throughout the exposures was examined. The putamen was targeted unilaterally by an ExAblate Neuro MRgFUS system operating at 220 kHz. Definity microbubbles were infused via a saline bag gravity drip at a rate of 4 µL/kg per 5 min. A cavitation emissions-based feedback controller was employed to modulate the acoustic power automatically according to prescribed target cavitation dose levels. BBB opening was measured by Gadolinium (Gd)-enhanced T1-weighted MR imaging, and the presence of potential micro-hemorrhages induced by the exposures was assessed via T2*-weighted MR imaging. A total of 12 treatment sessions were carried out across four patients, with target cavitation dose levels ranging from 0.20-0.40. BBB permeability in the targeted putamen was elevated successfully in all treatments, with a 14% ± 6% mean increase in Gd-enhanced T1-weighted MRI signal intensity relative to the untreated contralateral side. No indications of red blood cell extravasations were observed on MR imaging scans acquired one day following each treatment session. The cavitation emissions-based feedback controller was effective in modulating acoustic power levels to ensure BBB permeability enhancement while avoiding micro-hemorrhages, however, further technical advancements are warranted to improve its performance for use across a wide variety of brain diseases.

The effects of acoustic pressure level on the heat transfer performance of a wavy channel: Calibrated RANS model with machine learning application

In high-tech industries, an improvement in heat transfer performance plays an important role. This investigation was carried out computationally to evaluate the heat transfer structure and flow properties of a wavy channel in a turbulent mode, taking into account various working conditions of the system. In this regard, three-dimensional numerical simulations were conducted utilizing a finite volume code and a machine learning-calibrated RANS model. Initially, the findings were evaluated with available experimental data, demonstrating the high precision of the calibrated RANS model (about 99%) in predicting the flow and heat transfer structure. In addition, the simulations were expanded to examine the effects of acoustic power level external sources as an active control method on the performance of heat transfer. Based on the findings, the heat transfer performance increased up to 27.27% due to increasing the flow momentum creating eddy flows, and enhancing the turbulence intensity using an acoustic power level external source.

From sonar to medical ultrasound—The impact of Paul Langevin

The technical developments and discoveries of Paul Langevin figuratively and literally powered an incredible spectrum of scientific achievement. The quartz transducer technology of his 1918 patent (Procédé et appareils d'émission et de réception des ondes élastiques sous-marines à l'aide des propriétés piézo-électriques du quartz. – French Patent No. 505,703) enabled a level of acoustic output power generally unavailable at ultrasonic frequencies along with an increase in detection sensitivity. While there were disputes as to who should have been included on this patent, its effect on the field of ultrasonics is clear. The impetus for this work was largely high-power sonar for military application but his reported observations of effects on fish and even humans ushered in a new era of ultrasound bioeffects investigations including those of the famous Loomis Laboratory and numerous others. This is arguably the genesis of the rich tradition of research in ultrasound bioeffects and helped drive the pursuit of diagnostic and therapeutic applications of ultrasound including work by such famous researchers as the Fry Brothers. This presentation will review the evolution of bioeffects from the Langevin’s work and its impact on the field of medical ultrasound.