Wave Sound Field Research Articles

Aerial intense ultrasonic source integrating the horn and vibrating plate

The components of conventional high-intensity aerial ultrasonic sources, including the horn, longitudinal vibrating resonance bar, and transverse vibrating plates, are usually constructed separately. In this paper, a compact ultrasonic source that integrates all component parts was developed. First, the structure of the ultrasonic source was designed by simulation analysis with the finite element method. Next, an actual ultrasonic wave source was manufactured, and its electrical characteristics, vibration characteristics, and sound pressure distribution characteristics were measured. The ultrasonic source formed a strong standing wave sound field in the air, even though the total length was one wavelength of the longitudinal vibration. For an input electric power of 10 W, a high sound pressure in the standing wave sound field of 3.44 kPa was obtained (sound pressure level of about 165 dB).

High performance isolation of circulating tumor cells by acoustofluidic chip coupled with ultrasonic concentrated energy transducer

The isolation of circulating tumor cells (CTCs) from whole blood is a challenging task. Although various studies on the separation of CTCs by acoustofluidic devices have been reported, difficulties still persist, such as the complicated equipment, high cost, and difficult operation. Those problems should be resolved urgently. Herein, we developed an acoustofluidic chip separation system coupled with an ultrasonic concentrated energy transducer (UCET) system for efficient separation of CTCs. In the separation system, the acoustically sensitive particles were pre-focused by inertial forces of the PDMS chip channel structure. Then, the particles with different sizes were separated by acoustic radiation forces (ARF). In this study, the circulating tumor cells was simulated (CTCs-like particles) by aminated mesoporous acoustically sensitive particles (MSN@AM) encapsulated carboxylate polystyrene microspheres (PS-COOH). Subsequently, efficient CTCs-like particles separation was achieved by the acoustofluidic chip coupling system. This study effectively separated polystyrene microspheres carrying acoustically sensitive particles (MSN@AM@PS-COOH). However, the MSNs agglomerates and PS microspheres without acoustically sensitive particles did not show phenomenon of separation. This method allows to efficiently separate 2 µm MSNs agglomerates，8.0–8.9 µm PS microspheres and 10–10.5 µm MSN@AM@PS-COOH particles. It is demonstrated that the CTCs-like particles show more sensitive response, longer moving distance, and more obvious separation effect at the condition of the low frequency traveling wave sound field (20 kHz from UCET). This system can maintain the same separation with reduced amount of reagents used for cancer detection. It may provide a reliable basis for sorting out CTCs efficiently from the whole blood of cancer patients.

Metamaterials: Design, modelling, simulation and implementation

Metamaterials are a new class of man-made compound materials with exceptional properties which are not found in nature. Thanks to their superior features, they are used in a variety of fields and industries such as microwave engineering, dispersion compensation, smart antennas, sensor identification, high-frequency battlefield communications, improved ultrasonic sensors, solar energy management for high-gain antennas, remote aerospace applications, vibration control, acoustic wave guiding, and energy harvesting. The microstructures in acoustic metamaterials are locally alternating. Over the past decade, acoustic metamaterials have gained increasing attention because of the ability to modify the sound wave field or vibration at inputs in ways that cannot be achieved using ordinary materials. In the meantime, acoustic metamaterials can possess negative modulus of elasticity, negative density, or anisotropic mass. These capabilities greatly increase the choice of materials and provide an unprecedented way to manipulate/attenuate wave propagation and vibrational and acoustic behavior of structures. Physiomechanical property improvements yielded major interests in metamaterials and thereby exploring the physics of such mechanisms, leading to excellent essential investigations related to the synthesis, development, and characterization of such advanced materials.

On acoustic natural frequencies of planar wave sound field connected two acoustic tubes with different cross sectional area and length (Theoretical consideration)

On acoustic natural frequencies of planar wave sound field connected two acoustic tubes with different cross sectional area and length (Theoretical consideration)

Method for Establishing a Traveling Wave Sound Field with Adaptive Control in a Water-Filled Sound Tube

The transfer function method is a common method for establishing a traveling wave field in a sound tube to measure the reflection and transmission coefficient of underwater material. The voltage applied to the secondary sound source can be calculated in accordance with the transfer matrix between the sound sources and hydrophones, then a traveling wave field can be established in the sound tube. However, the transfer function must be remeasured when the measurement frequency needs to be changed. A checking procedure of the traveling wave field in the sound tube is essential before measuring underwater acoustic material. If it is not an accurate traveling wave field, the secondary sound source signal should be corrected until the traveling wave field meets the requirements. To address these problems, an adaptive control method for generating plane traveling waves is proposed. The phase difference of sound pressures measured using the two hydrophones between the secondary sound source and the sample is used as the objective function in the adaptive algorithm, and the amplitude and phase of the secondary sound source can be obtained using the adaptive control system in the frequency domain. When a traveling wave field is formed, the reflection and transmission coefficient of the sample can be measured at the same time. With this method, the procedure of testing the traveling wave field is omitted. If the state of the primary sound source changes, the signal form of the secondary sound source can be changed immediately. Therefore, the efficiency of material measurement is improved. Theoretically, this method can obtain the most matching signal form of the secondary sound source, such that the accuracy of this method is remarkably high. Simulation and experimental results in this paper show that the measurement accuracy is reliable within the frequency range of 100–2500 Hz.

Drying of wet cloth by aerial intense standing wave field formed by two sets of transverse vibrating plate type ultrasonic sound sources

Recently, there has been research into drying by applying an ultrasonic vibrator directly to wet clothes. However, this method may damage the fabric and decorations of clothing because the ultrasonic vibrator is in direct contact with the wet clothing. Therefore, we would like to dry wet clothes without contact using an aerial intense ultrasonic wave. In this paper, an intense standing wave sound field was formed in the air using two sets of transverse vibrating plate type ultrasonic sound sources, and a cloth larger than the wavelength of the sound wave in the ultrasound field was dried. We compared the moisture content on dry basis, drying rate, and drying time of the drying samples, and determined the differences in drying effect depending on differences in the installation position of the drying samples in the ultrasound field.

高校物理教科書「音波分野」の検討 音波の記述は圧力波で統一することを提案する

高校物理教科書「音波分野」の検討 音波の記述は圧力波で統一することを提案する

Acoustic streaming outside spherical particles and parameter analysis of heat transfer enhancement

Acoustic streaming effects can play an important role for promoting heat and mass transfer. Considering the viscous loss inside the viscous boundary layer on the particles surface, a numerical model for the acoustic streaming outside a two-dimensional spherical particle in a plane standing wave sound field is established, and the distribution characteristics of the acoustic streaming outside the particles are simulated by the numerical method of separation time scale. The reliability of the numerical simulation is verified by comparing the simulation results with the corresponding analytical solution. Based on this, we simulate the acoustic streaming distribution characteristics outside the particles under different Reynolds numbers and Strouhal numbers, and the acoustic parameters for heat transfer enhancement by acoustic streaming are analyzed. The numerical studies show that as the Strouhal or Reynolds numbers increase, the acoustic streaming region inside the boundary layer shrinks, but the shear force increases, and the vortex structure outside the particles increased from 4 to 8. when the particles are located in different positions of the plane standing wave sound field, the acoustic streaming has a rich flow pattern structure. The parameter analysis of the influence of acoustic streaming on convective heat transfer shows that the strong acoustic streaming motion formed by the acoustic waves with the small Strouhal number and large Reynolds number can greatly promote the heat and mass transfer process. For the small Strouhal number, the inner vortex in the viscous boundary layer is the main mechanism affecting the heat and mass transfer process. And increasing the Reynolds number is the most direct and effective means to strengthen the heat and mass transfer process The study helps to reveal the mechanism of acoustic to enhance the heat transfer of objects. In addition, the numerical method can be used to evaluate the external acoustic streaming characteristics of any physical model.

Application of the Euler-Maclaurin Sum Formula to Obtain a Closed form Analytical Solution for Acoustical and Heat Diffusion in a Partially Bounded Region

Green’s function in the Laplace transform domain for the sound wave field in an infinite area between two parallel reflecting planes may be represented as an infinite series of images caused by the planes. Based on a comparison of the wave equation and the diffusion equation, the Green’s function representation as an infinite series for diffusion in the same region is directly obtained. A closed form expression in space time for the diffusion problem is obtained by applying the Euler-Maclaurin sum formula to a modified diffusion form of the series in the Laplace transform domain and then inverting to the time domain. Using several sets of numerical values for system parameters applicable to acoustic diffusion in the region, numerical comparisons of the infinite series vs Euler-Maclaurin closed form representation of the Green function is presented. Comparison of the infinite series vs Euler-Maclaurin transient response to an exponential and constant input are presented for cases of acoustical noise diffusion and heat diffusion respectively. Transfer function comparisons are given for the diffusion models along with the use of the closed form representation in a model-based control scheme.

Mechanism of Cloud Droplet Motion under Sound Wave Actions

AbstractSound waves have proven to be effective in promoting the interaction and aggregation of droplets. It is necessary to theoretically study the motion of particles in a sound field to develop new acoustic technology for precipitation enhancement. In this paper, the motion of cloud droplets due to a traveling sound wave field emitted from the ground to the air is simulated using the motion equation of point particles. The force condition of the particles in the oscillating flow field is analyzed. Meanwhile, the effects of droplet size, sound frequency, and sound pressure level (SPL) on the velocity and displacement of the droplets are also investigated. The results show that Stokes force and gravity play a dominant role in the falling process of cloud droplets, and the effect of the sound wave is mainly reflected in the fluctuation of velocity and displacement, which also promotes the displacement of cloud droplets to a certain extent. The maximum displacement increments of cloud droplets of 10 µm can reach 9200 µm due to the action of sound waves of 50 Hz and 143.4 dB. The SPL required for a noticeable velocity fluctuation for droplets of 10 µm with frequency of 50 Hz is 88.2 dB. When SPL < 100 dB and frequency > 500 Hz, the effect is negligible. The cloud droplet size plays a significant role in the motion, and the sound action is weaker for larger particles. For a smaller sound frequency and higher SPL, the effect of the sound wave is more prominent.

Rubber-Liquid Resonator

The acoustic characteristics of a rubber-liquid resonator are calculated, combining the properties of an empty rubber cavity, a Helmholtz resonator, and a water–air resonator, gas bubble in a viscoelastic medium and in a shell, and a bubble in a liquid. The equation of the forced oscillations of the resonator in the sound wave field is obtained by applying the principle of least action. The eigenfrequency of the resonator is calculated. The following sound energy dissipation mechanisms are considered: due to the shear viscosity of rubber, the viscosity of liquid in the neck, heat loss in the air chamber, and radiation loss. Experimental data are presented. Possible resonator applications are discussed.

Interaction between particles and bubbles driven by ultrasound: Acoustic radiation force on an elastic particle immersed in the ideal fluid near a bubble.

A theoretical model is proposed to investigate the acoustic radiation force on the elastic particle for coupled particle-bubble system. Based on the sound scattering theory, an analytical expression of the force function is obtained for the particle in plane wave sound field. Numerical simulations are presented for elastic particle of stainless steel, steel or brass. The results reveal that the presence of bubbles can affect the feature of radiation force curves of particles. The force curve fluctuates, and negative force emerges in the small kR1 region for certain distance between the bubble and particle. There are more sharp peaks and dips in the curves because of the resonance of the elasticity of the system and the resonant peaks of the acoustic radiation force transfer to low frequencies when the size of elastic particle is increased. The approximate positive flat region is shortened because of the presence of bubble, which may help to optimize the size ranges of particle for acoustic screening. This study provides for improvement of the acoustic manipulation theoretical model.

DOA Estimation Performance With Circular Arrays in Sound Fields With Finite Rate of Innovation

A novel Direction-of-Arrival (DOA) estimation method based on a plane wave sound field model was recently proposed for circular microphone arrays [1] . This article presents a detailed theoretical analysis of the method that relies on a Finite Rate of Innovation (FRI) assumption, investigating the impact of different theoretical acoustic source models. The method's estimation accuracy, and robustness against noisy measurement data and deviations from the model are investigated. The estimation performance is validated and assessed on the basis of results obtained from both simulations and experimental data.

Acoustic Radiation Force and Torque on Small Particles as Measures of the Canonical Momentum and Spin Densities.

We examine acoustic radiation force and torque on a small (subwavelength) absorbing isotropic particle immersed in a monochromatic (but generally inhomogeneous) sound-wave field. We show that by introducing the monopole and dipole polarizabilities of the particle, the problem can be treated in a way similar to the well-studied optical forces and torques on dipole Rayleigh particles. We derive simple analytical expressions for the acoustic force (including both the gradient and scattering forces) and torque. Importantly, these expressions reveal intimate relations to the fundamental field properties introduced recently for acoustic fields: the canonical momentum and spin angular momentum densities. We compare our analytical results with previous calculations and exact numerical simulations. We also consider an important example of a particle in an evanescent acoustic wave, which exhibits the mutually orthogonal scattering (radiation-pressure) force, gradient force, and torque from the transverse spin of the field.

Insights into agglomeration and separation of fly-ash particles in a sound wave field.

The efficiency of fine particle removal by using traditional devices is relatively low. Acoustic agglomeration is an effective pretreatment method that agglomerates particles before they enter a particulate control device so that they can be easily removed. The movements of particles exposed in a sound wave field were captured using a high-speed camera in this study. Agglomeration and separation of two particles were directly observed. Photographs were analyzed frame by frame to obtain motion information. A model was constructed, and COMSOL Multiphysics software was employed to simulate their relative motions. The simulation results matched the experimental results well. The conditions under which an aggregate consisting of two particles will be separated by a sound wave were calculated. The calculated results revealed that a non-breakable region exists: when sizes of primary particles are within this region, agglomerates will not be separated into smaller particles, but outside this region, agglomerates can be separated. The observation of particle motion deepens understanding of acoustic agglomeration and separation processes taking place in the agglomeration chamber. The calculation of separation of agglomerates can guide enhancement of acoustic agglomeration processes.

Aerial ultrasound source with a circular vibrating plate attached to a rigid circumferential wall

We fabricate a transverse vibrating plate attached to a rigid wall integrated at the circumference of a circular vibrating plate that allows a strong sound wave field to be formed in the area encoded by the vibrating plate and rigid wall by installing a wall such as a reflective plate on the rigid wall. The design method for the circular vibrating plate attached to a rigid circumferential wall is investigated. A method of forming a strong standing wave field in an enclosed area constructed with a vibrating plate, cylindrical reflective plate, and parallel reflective plate is developed.

Active room compensation for sound reinforcement using sound field separation techniques.

This work investigates how the sound field created by a sound reinforcement system can be controlled at low frequencies. An indoor control method is proposed which actively absorbs the sound incident on a reflecting boundary using an array of secondary sources. The sound field is separated into incident and reflected components by a microphone array close to the secondary sources, enabling the minimization of reflected components by means of optimal signals for the secondary sources. The method is purely feed-forward and assumes constant room conditions. Three different sound field separation techniques for the modeling of the reflections are investigated based on plane wave decomposition, equivalent sources, and the Spatial Fourier transform. Simulations and an experimental validation are presented, showing that the control method performs similarly well at enhancing low frequency responses with the three sound separation techniques. Resonances in the entire room are reduced, although the microphone array and secondary sources are confined to a small region close to the reflecting wall. Unlike previous control methods based on the creation of a plane wave sound field, the investigated method works in arbitrary room geometries and primary source positions.

Dynamic spin-current generation in hybrid structures by sound wave

We have developed the theory of spin transport transverse to the interface in metal/ferromagnetic insulator hybrid structures under the spin Seebeck effect conditions. We have calculated the deviation of the conduction electrons spin temperature from equilibrium under conditions of saturation of resonance interaction between the electrons and a sound wave field. We have demonstrated that the conduction electrons spin subsystem, when excited under the above conditions, generates a spin-wave current in a nonconducting ferromagnetic of the metal/ferromagnetic insulator hybrid structure being in a nonuniform temperature field. In addition, the spin-wave current generation in the ferromagnetic has a resonance nature. We have analyzed the approximation of effective parameters, when each of the considered subsystems (conduction electrons, magnons, and phonons) is characterized by its effective temperature.

Modeling linear Rayleigh wave sound fields generated by angle beam wedge transducers

In this study, the reciprocity theorem for elastodynamics is transformed into integral representations, and the fundamental solutions of wave motion equations are obtained using Green’s function method that yields the integral expressions of sound beams of both bulk and Rayleigh waves. In addition to this, a novel surface integral expression for propagating Rayleigh waves generated by angle beam wedge transducers along the surface is developed. Simulation results show that the magnitudes of Rayleigh wave displacements predicted by this model are not dependent on the frequencies and sizes of transducers. Moreover, they are more numerically stable than those obtained by the 3-D Rayleigh wave model. This model is also applicable to calculation of Rayleigh wave beams under the wedge when sound sources are assumed to radiate waves in the forward direction. Because the proposed model takes into account the actual calculated sound sources under the wedge, it can be applied to Rayleigh wave transducers with different wedge geometries. This work provides an effective and general tool to calculate linear Rayleigh sound fields generated by angle beam wedge transducers.

Numerical calculation of particle movement in sound wave fields and experimental verification through high-speed photography

Inhalable particulate matter, especially PM2.5, is a main pollutant in China that is harmful to both human health and the atmosphere. The PM2.5 removal efficiency of traditional dust removal devices such as ESP is low, and pretreatment must be conducted before dust enters the dust remover. Acoustic agglomeration is a pretreatment technology that uses high-intensity sound waves to agglomerate and develop fine particles; this method improves the PM2.5 removal efficiency of traditional dust removal devices. In a sound wave field, fine particles are carried by a medium (air in this study) and vibrate at different amplitudes when they vary in size. Thus, relative movement is generated and subsequently, particles increasingly collide and agglomerate. In this study, the movements of differently sized particles in traveling and standing wave sound fields are calculated, including the velocities, displacements, and amplitudes. Re<1 in this study, and the viscous force in the Stokes region is chosen as the main force. High-speed photography is employed to observe particle movement in different sound wave fields. The vibration speed and amplitude determined by analyzing the tracks in the photos are consistent with the calculated results. The movement of fine particles in a sound field with different conditions must be studied to identify the mechanisms of acoustic agglomeration.