Ultrasonic Source Research Articles

A parametric resonance based capacitive ultrasonic transducer for wireless power transfer in air

Capacitive ultrasonic transducers have been in use for many years for various applications such as medical imaging, wireless power, sensing, and nondestructive testing. Typically, capacitive transducers require a DC bias or electret in order to operate efficiently and with high sensitivity. This makes them less desirable for applications such as wireless power transfer or energy harvesting, where a passive piezoelectric transducer may be preferred. Recently, it was shown that the requirement of a DC bias can be overcome by driving the capacitive transducer into parametric resonance using ultrasound (Surappa et al., Appl. Phys. Lett. 111(4), 043503). In this work, we present the operation of the first ever biasless, chargeless capacitive parametric ultrasonic transducer (CPUT) in air and demonstrate the utility of such a system for acoustic power transfer and sensing. Experiments performed in air show that the CPUT has an open-circuit sensitivity of more than 100 mV/Pa and is able to recover 31 µW at a distance of 10 cm from a 50 kHz ultrasonic source in the absence of a DC bias.

Ultrasonic-assisted laser welding on AISI 321 stainless steel

Ultrasonic-assisted laser welding on 321 stainless steel has been carried out to find out the effect of ultrasonic energy input on the microstructure and strength of the weld metal. Ultrasonic energy was transmitted from a transducer, via two waveguides and hard alloy indenter fixed perpendicularly on the workpiece surface. Real-time ultrasonic oscillation amplitude distributions over the workpiece surface and in the bulk of the workpiece have been obtained using the laser Doppler vibrometry and finite element simulation which allowed estimating the close to reality ultrasonic energy input values. The real energy input was at least two orders of magnitude less than that calculated from the nominal ultrasonic source power. The welded joints have been characterized for microstructure, microhardness, and tensile strength. It was shown using TEM that higher microhardness of the sonicated welded joint is due to high concentration of split dislocations induced by ultrasonics. The tensile strength of the ultrasonic-assisted-welded joint depended on the ultrasonic energy input and was higher than that of the base metal in case of sonication by 600 W output power.

Air Ultrasonic Signal Localization with a Beamforming Microphone Array

Nondestructive testing methods are used to inspect and test materials and components for discontinuities or differences in mechanical characteristics. Phased array signal processing techniques have been widely used in different applications, but less research has been conducted on contactless nondestructive testing with passive arrays. This paper presents an application of beamforming techniques analysis using a passive synthetic microphone array to calculate the origin and intensity of sound waves in the ultrasonic frequency range. Acoustic cameras operating in the audible frequency range are well known. In order to conduct measurements in higher frequencies, the arrangement of microphones in an array has to be taken into consideration. This arrangement has a strong influence on the array properties, such as its beam pattern, its dynamics, and its susceptibility to spatial aliasing. Based on simulations, optimized configurations with 16, 32, and 48 microphones and 20 cm diameter were implemented in real experiments to investigate the array resolution and localize ultrasonic sources at 75 kHz signal frequency. The results show that development of an ultrasonic camera to localize ultrasonic sound sources is beneficial.

Piezoelectric Energy Harvesting with an Ultrasonic Vibration Source

A piezoelectric energy harvester was developed in this paper. It is actuated by the vibration leakage from the nodal position of a high-power ultrasonic cutting transducer. The harvester was excited at a low displacement amplitude (0.73 µmpp). However, its operation frequency is quite high and reaches the ultrasonic range (24.4 kHz). Compared with another low frequency harvester (66 Hz), both theoretical and experimental results proved that the advantages of this high frequency harvester include (i) high current generation capability (up to 20 mApp compared to 1.3 mApp of the 66 Hz transducer) and (ii) low impedance matching resistance (500 Ω in contrast to 50 kΩ of the 66 Hz transducer). This energy harvester can be applied either in sensing, or vibration controlling, or simply energy harvesting in a high-power ultrasonic system.

1P4-6 Characteristics of particle size distribution of agglomerates in an ultrasonic source with a cylindrical rigid wall

1P4-6 Characteristics of particle size distribution of agglomerates in an ultrasonic source with a cylindrical rigid wall

3P4-9 Development of 58 kHz compact ultrasonic sound source using a circular plate with circumferential excitation

3P4-9 Development of 58 kHz compact ultrasonic sound source using a circular plate with circumferential excitation

Study on Reciprocal Models for Magneto-Acousto-Electrical Tomography With Coil Detection

Magneto-Acousto-Electric Tomography with coil detection, known as Magneto-Acousto-Electric Tomography with Magnetic Induction (MAET-MI), is a non-contact resistivity-based imaging method that employs a coil to detect the induced current generated by the ultrasound in biological tissue, which lie under a static magnetic field. To reconstruct an image of the tissue's conductivity, we propose a reciprocal model to describe the relationship between the inducted voltage of a coil and its conductivity. Previous work on the reciprocal theorem demonstrates that reconstructing conductivity using this method is effective. The forward and inverse problem are usually not verified both numerically and experimentally. In this paper, different approaches are adopted to calculate the forward and the inverse problems for verification of the reciprocal model. This verifies that the reconstruction method based on electrode detection can be applied to MAET-MI. This means that the inverse problem of MAET-MI can be transformed into an inverse source reconstruction of a wave equation based on the coil detection. In the forward problem, the moment method is employed to calculate the Radon transform and generate the ultrasonic signals. For the inverse problem, the filtered back projection method is chosen to reconstruct the ultrasound sources, which are related to the curl of the current density in the reciprocal process. Based on the curl of the current density in the reciprocal process, four sets of correlation coefficients of the original and reconstructed images' model are all greater than 90%. The uniform error criterion is obtained via multiple reconstructions and comparison of multiple models. The reciprocal model exhibits a good uniformity and stability when describing the actual physical process. It also provides additional effective ideas for solving the inverse problem quickly to reconstruct the ultrasonic sources, which is corresponding to the actual distribution of the conductivity.

A new approach in physical modeling for velocity anisotropy study

Special automated equipment is constructed for ultrasonic velocity measurements at various incidence angles of waves that is necessary for estimation of anisotropy parameters of rocks. The equipment includes hydraulic press for simulation of vertical pressure in the Earth, at a range up to 40 MPa and computer controlled positioning system that provides precise independent positioning of ultrasonic source and receiver. This setup enables us to perform reliable velocity measurements at the angle interval from 15° to 90° and additional single measurement at 0°. The minimum step of a transducer position in 15°-90° range is 8.1'. As an example on anisotropy study, we perform physical modeling of wave propagation in artificial sample of transversely isotropic (TI) symmetry, which represents a model of fractured rock. Using experimental setup, we acquire P-wave velocity data for plate-stack model with vertical axis of symmetry formed by acrylic 1 mm thick sheet plates. Using measured velocities, we estimate Thomsen’s anisotropy parameters e and δ, and get dependence between the velocity of P-waves and symmetry axis of the model. . In our oncoming research, the upgraded Ultrasonic Measuring System will be supplemented by multicomponent transducers similar to those described in Chichinina et al. (2009), which allow simultaneous recording of P, SV and SH waves at each data point.

Low-Frequency Ultrasonic Tomography: Mathematical Methods and Experimental Results

This paper describes investigation of the possibilities of low-frequency ultrasonic tomography in medicine. The main application is the development of tomographic methods for differential diagnosis of breast cancer. To solve the inverse problem, a mathematical model is used that describes both the phenomena of diffraction and refraction and the absorption of ultrasound in an inhomogeneous medium. The algorithms developed for reconstructing the velocity structure were evaluated using the test bench for experimental studies. Broadband ultrasonic sources in the 50–600 kHz range were used for sounding. A Teledyne Reson TC4038 hydrophone with a sensitivity of approximately 4 µV/Pa and a frequency range of 10–800 kHz was used as a receiver. A Teledyne Reson VP1000 preamplifier was used to amplify the signals. The studies were carried out on phantoms with acoustic parameters close to the properties of human soft tissues. A layerwise model was used to reconstruct the three-dimensional velocity structure. The sound speed cross-sections reconstructed from the experimental data have a resolution of approximately 2 mm, while the central wavelength is approximately 4 mm. An important result of the work is an experimental confirmation of the correspondence of the model to physical processes.

Cavitation clouds in gas-containing liquids block low-frequency components of ultrasonic waves

Intense single-frequency ultrasonic waves generate cavitation clouds in liquids, while at the same time, the pulsating cavitation bubbles emit broadband noise. In gas-containing liquids such as soda and beer, an ultrasonic source with a driving frequency of 20 kHz is shown to easily stimulate the formation of dense cavitation clouds and large cavitation bubbles in experiments. The acoustic signal is acquired at the boundary (opposite the ultrasonic source) just outside the cavitation cloud. Analysis of this signal using the fast Fourier transform reveals a gap in the acoustic spectrum at low frequencies, which means that the low-frequency acoustic waves cannot penetrate the cavitation area. However, these low-frequency waves can be detected in the cavitation cloud, which means that they are localized there. Through a linear analysis of a nonlinear equation for soundwave propagation in bubbly liquids, we can interpret the localization observed in the experiments. When soundwave frequencies are close to the resonance frequency, the absorption is strong and the corresponding frequencies form a forbidden band in the frequency spectrum unless the void fraction of the bubbles is too small. The intense ultrasonic wave that we applied in the experiment is of a frequency that is slightly smaller than the resonance frequency and can penetrate the cavitation cloud with some attenuation, driving the bubbles to pulsate violently. In this case, noise with frequencies in the forbidden band radiated by nonlinearly oscillating bubbles cannot penetrate the cavitation cloud and can only exist around local bubbles.

The Effect of Ultrasonic Wave Exposure on The Chlorophyll-a, b And Carotene Content of Nannochloropsis sp.

Determination of chlorophyll-a, b and carotene content in microalgae is strongly dependent on the destruction of its cell wall during extraction process. Harvesting of microalgae is important because it will influence the nutrition content. The objective of present work is to optimize harvesting of Nannochloropsis sp by application of ultrasonic wave with frequency of 40 KHz under different exposure time. There were 3 treatments, i.e. exposure time of 5, 10 and 15 minutes. The chlorophyll-a, b, and carotene content were measured to gauge the effect of treatments. The result revealed that the cell wall of Nannochloropsis sp which made from carbohydrate were successfully broken by ultrasonic source equipment. It showed that the exposure time of 5, 10 and 15 minutes affected cell wall’s breaking percentage of Nannochloropsis sp cell by 10,35; 32,15; and 72,09 %, respectively. The longer exposure time of ultrasonic wave, the higher content of chlorophyll-a, b, and carotene.

Virtual X-Ray Diffractometer using Acoustic Wave for Material Science Education

In this research, virtual X-Ray Diffractometer (XRD) using acoustic wave for material science education has been proposed. Acoustic wave with frequency in ultrasonic range has been used to characterize acoustic crystal structures. The dimensions of model structure, which are in order of ultrasonic wavelength region, have been formed by three dimensional printer (3D printer) and cotton swab. The angle of ultrasonic source and detector have been swept to record reflected wave signal of each angle. The peak of each angle have been selected to calculate lattice spacing by Bragg’s law and then compared with the implemented structure. The results show signal peaks of each diffracted angle. The experimental results showed that the lattice spacing values obtained from acoustic experiment were in good agreement with the measured values of the implemented structure. This virtual XRD system provide to be an efficient tool for understanding about crystal structure characterization.

On Cuba, diplomats, ultrasound, and intermodulation distortion

This paper analyzes how ultrasounds could have unintentionally led to the AP news recordings of metallic sounds heard by diplomats in Cuba. Beginning with screen shots of the acoustic spectral plots from the AP news, we reverse engineered ultrasonic signals that could lead to those outcomes as a result of intermodulation distortion with non-linearity in the acoustic transmission medium. We created a proof of concept ultrasonic device that amplitude modulates a signal over an inaudible ultrasonic carrier. When a second inaudible ultrasonic source interfered with the primary source, intermodulation distortion created audible byproducts that share spectral characteristics with audio from the AP news. Our conclusion is that if ultrasound played a role in harming diplomats in Cuba, then a plausible cause is intermodulation distortion between ultrasonic signals that unintentionally synthesize audible tones. In other words, acoustic interference without malicious intent to cause harm could have led to the audible sensations in Cuba.

Effect of geometrical configuration of reactor on a ZrP nano-dispersion process using ultrasonic irradiation

This study investigated the position of ultrasonic irradiation source and reactor geometry on fragmentation rate of a layered compound, α-zirconium phosphate (α-ZrP). By numerically solving the acoustic pressure distribution using COMSOL Multiphysics®, it is clarified the mechanism whereby the operating factors influenced the α-ZrP dispersion to make a suggestion of guideline of the process design method. Two vessels made of glass with a flat-bottom and a spherical-bottom, respectively, were used. Although the flat-bottom vessel at lower horn position showed the best performance of fragmentation, the region of high acoustic pressure field in the flat bottom vessel sharply narrowed and the transmittance became prominently low. On the other hand, no significant difference of the transmittance value in the spherical bottom vessel between the cases of low and high horn positions could be observed and the spherical bottom vessel was robust for the horn position. These results suggest that not only the magnitude of acoustic pressure but also the size of high acoustic pressure region is also an important factor and a spherical bottom vessel is one of suitable shape which gives large size of high acoustic pressure region regardless of the horn position.

Particle filter algorithm based spatial motion tracking of football landing location

In order to improve the accuracy of the tracking of football landing location, a football landing location and spatial motion tracking system based on APRBA multi-camera was proposed. First of all, the study of football movement locus model was conducted. Without considering the speed limit and direction restriction, Bayesian state evolution model was constructed, and based on path loss model, the moving target positioning observation model was established. Secondly, by using the ultrasonic food source localization of the proposed APRBA algorithm and the next target prediction, the particle filter algorithm was improved to realize the effective improvement of target tracking accuracy. Finally, the effectiveness of the proposed target tracking algorithm was verified in the tracking experiment of the moving target model.

Deformation and impregnation of droplets containing abrasive grains using intense aerial ultrasonic waves

For efficient impregnation, it is important to improve the wettability between the samples used. However, the traditional impregnation method using ultrasonic waves suffers from the following problems: that the vibration source must be brought into direct contact with the sample and impregnation with liquids with high viscosities is difficult. Also, the method has the possibility that impurities will be mixed in the sample when bringing the ultrasonic vibration source directly into contact with the sample. Therefore, we investigated the use of intense aerial ultrasonic waves as a new noncontact method of impregnating into meshes while observing the extent of the droplet spread. In this study, we observed droplet deformation and impregnation when changing the droplet volume and input power and after installing a sound waveguide for focusing the sound wave. Consequently, we were consequently able to demonstrate the impregnation of droplets into the mesh.

Welding characteristics of Cu and Al plates using planar vibration by a dumbbell-shaped ultrasonic complex vibration source

Conventional ultrasonic welding uses vibrations with a one-dimensional linear locus. Because the vibration energy is small, this method suffers from the drawbacks that the weld strength is low and variable depending on the installation direction of the welding sample. Our previous studies have revealed that the weld strength can be improved by using vibrations with a two-dimensional planar locus. However, the question of whether welding using planar vibration could be achieved in a short weld time and the relationship between the installation direction of the welding sample and the weld strength remained unclear. Therefore, these issues were addressed by the investigation described in this paper. Consequently, we demonstrated that welding using planar vibration reaches a high strength in a shorter weld time than conventional linear vibration and that stable welding can be achieved independently of the installation direction of the welding sample.

Development of aerial ultrasonic source using cylinder typed vibrating plate with axial nodal mode

We developed a high-power aerial ultrasonic source with a cylinder typed vibrating plate combined with two rigid walls that can be directly connected to a pipe in order to solve the difficulty in connecting an ultrasonic source to a pipe containing particles while preventing the particles from leaking. The structure of the vibrating plate combined with two rigid walls that do not vibrate and can obtain a high sound pressure in the space inside the vibrating plate was designed using the finite element method (FEM). We found that the aerial ultrasonic source using the designed vibrating plate slightly vibrates at the rigid walls as designed using FEM and can be connected to other devices. In addition, the obtained sound pressure was around 8.0 kPa (172 dB) at an input electrical power of 7 W.

Partial Discharge Ultrasound Detection Using the Sagnac Interferometer System.

Partial discharge detection is crucial for electrical cable safety evaluation. The ultrasonic signals frequently generated in the partial discharge process contains important characteristic information. However, traditional ultrasonic transducers are easily subject to strong electromagnetic interference in environments with high voltages and strong magnetic fields. In order to overcome this problem, an optical fiber Sagnac interferometer system is proposed for partial discharge ultrasound detection. Optical fiber sensing and time-frequency analysis of the ultrasonic signals excited by the piezoelectric ultrasonic transducer is realized for the first time. The effective frequency band of the Sagnac interferometer system was up to 175 kHz with the help of a designed 10 kV partial discharge simulator device. Using the cumulative histogram method, the characteristic ultrasonic frequency band of the partial discharges was between 28.9 kHz and 57.6 kHz for this optical fiber partial discharge detection system. This new ultrasound sensor can be used as an ideal ultrasonic source for the intrinsically safe detection of partial discharges in an explosive environment.

Air-coupled fiber Fabry-Perot ultrasonic sensor formed by diaphragm for seismic physical model imaging

We presented a miniature fiber ultrasonic sensor based on the principle of Fabry-Perot(F-P) interferometer, which comprises a single-mode fiber(SMF) spliced with a hollow core fiber (HCF), whose end face is adhered with UV glue(NOA68). The interface of NOA68 diaphragm-air as one of the two interfaces of F-P cavity is sensitive to ultrasonic wave due to its low Young’s modulus. Thus, it has the ability to detect weak ultrasonic wave reflected from seismic physical model (SPM) in air. Furthermore, the compact sensor has a characteristics to identify orientation of ultrasonic source because of its perfectly symmetrical structure and is capable of detecting wide ultrasonic frequency range from 300 KHz to 5 MHz. The spectral band-side filter technique is used for the interrogation of ultrasonic signal. As expected, using the designed sensing probe, we can reconstruct the SPM in 2D and 3D by the time-of-flight approach.