Acoustic Phase Shift Research Articles

Generation of high-order focused acoustic vortices and multiplexed beams using Dual-Channel metamaterials

Focused vortex beams have attracted considerable research attention due to their unique acoustic properties, and have been explored in medical imaging, biomedical therapy, and particle manipulation. Here, an acoustic metamaterial vortex generator (AMVG) is designed to realize a multiplexed focusing acoustic vortex (MFAV) with multiple-order topological charges (TCs). The proposed AMVG is composed of several fanlike sectors with two high transmission channels per unit, which can flexibly modulate the transmitted phase shift in two separate frequency bands. In contrast to conventional acoustic metamaterial-based vortices, the design strategy provides a new degree of freedom, i.e., frequency, that may extend to the agile tailoring of multi-band independent vortices, significantly enhancing the information encoded in the acoustic metamaterial. Acoustic transmission and phase shift of the dual-channel unit are investigated theoretically and demonstrated in simulations using the finite element method. The focal position and TC of the MFAVs can be modulated by simply adjusting the cavity length of the unit cell and even only the sector order. Furthermore, we implement three-dimensional anechoic experiments to verify the effectiveness of the off-axial MFAVs by the designed AMVG. These multiplexed focusing vortices offer a technical advance to tackle the rising challenges in the fields of acoustic signal processing and communication systems.

Effect of acoustic diffraction phase shift on caustic structure in deep sea convergence zone

The constant phase shift <inline-formula><tex-math id="M1">\begin{document}$- {{\text{π}}}/{2}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="20-20220763_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="20-20220763_M1.png"/></alternatives></inline-formula> generated by a turning point is an ideal approximation under high frequency conditions. In fact, when sound waves pass through a turning point, it will travel horizontally for a certain distance in the form of inhomogeneous plane wave and then be refracted back. At this time, a functional phase shift should also be included at the turning point. In addition, a refracted ray will bring about reflection phase shift when the turning point is close to the waveguide edge. These two kinds of phase shifts which are associated with the diffraction phenomenon are called diffraction phase shifts in this paper and are more notable when the frequency goes down. In order to accurately obtain the caustic structure at low frequency, the diffraction phase shift is used to correct the classical ray theory in calculating ray skip distance, traveling time, and group velocity in this work. On this basis, a simple and explicit analytical model is proposed which is suitable for calculating the low frequency deep water caustics. The numerical study of the first upper convergence zone in the complete deep water sound channel shows that there are three caustic lines in the refracted-refracted (RR) convergence zone and four caustic lines in the refracted surface-reflected (RSR) convergence zone under the condition of high frequency hypothesis. When the diffraction phase shifts at low frequency are included, and compares with high frequency results, it is found that the horizontal beam displacement caused by the reflection phase shift will make the RR caustics horizontally move towards the source and also lead the RSR rays to generate several new caustics, while the beam displacement caused by sound propagating in the form of inhomogeneous plan wave will make the RR caustics horizontally move away from the sound source. Accompanied with the increased frequency, the diffraction effect will decrease, and the caustic structure gradually tends to the classical ray theory results. The reliability of the correction results is verified by the normal mode theory. The model proposed in this work makes up for the deficiency of classical ray theory.

Acoustic CO2 Gas Sensor Based on Phase Difference Measurement

In this research, an acoustic sensor has been successfully built to measure the concentration of CO2 gas in a mixture of gases (N2 and CO2). The nitrogen and carbon dioxide gases used are ultra-high purity (UHP) gas. The measurement parameter used is the speed of sound by utilizing the phase shift between ultrasonic wave signals that are sent and received continuously. The acoustic method in this research is by using the speaker as an ultrasonic wave transmitter, and the microphone as an ultrasonic wave receiver emitted by the speaker on the gas medium. This acoustic phase shift method is very sensitive to be used to determine the speed of sound on a gas medium. From the sensor testing, the sensor has good linearity in detecting changes in CO2 concentration in the gas mixture. The sensor test results have been validated theoretically and obtained an RMS error of 3.36 (3.36% with a maximum concentration of 100%), this proves that the work of the sensor is in accordance with the theory. In addition to theoretical validation, the work of the sensor has also been validated by looking at the direct relationship between sensor input and output through the inverse function, and an RMS error of 3.51 (3.51% with a maximum concentration of 100%) is obtained. From the overall results obtained, the acoustic CO2 gas sensor that is built can detect changes in CO2 concentrations in the gas mixture accurately, fabrication of the sensor is easy to do, and the costs required in the manufacturing process are cheap.

Computationally efficient source grid selection and source interpolation in computational aeroacoustics applied to an axial fan.

The noise generation of an axial fan is mainly caused by flow-induced noise and can therefore be extracted from its aeroacoustics. To do so, a hybrid approach separating flow and acoustics is well suited due to its low Mach number. Such a computationally efficient hybrid workflow requires a robust conservative mesh-to-mesh transformation of the acoustic sources as well as a suitable mesh refinement to guarantee good convergence behavior. This contribution focuses on the mesh-to-mesh transformation, comparing two interpolation algorithms of different complexity towards the applicability to the aeroacoustic computation of an axial fan. The basic cell-centroid approach is generally suited for fine computational acoustic (CA) meshes and low phase shift, while the more complex cut-volume method generally yields better results for coarse acoustic meshes. While the cell-centroid interpolation scheme produces source artifacts inside the propagation domain, a grid study using the grid convergence index shows monotonic convergence behavior for both interpolation methods. By selection of a proper size for the source grid and source interpolation algorithm, the computational effort of the experimentally validated simulation model could be reduced by a factor 4.06.

Can dark neutrino interactions phase out the Hubble tension?

New interactions of neutrinos can stop them from free streaming even after the weak interaction freeze-out. This results in a phase shift in the cosmic microwave background (CMB) acoustic peaks which can alleviate the Hubble tension. In addition, the perturbations in neutrinos do not decay away on horizon entry and contribute to metric perturbation enhancing the matter power spectrum. We demonstrate that this acoustic phase shift can be achieved using new interactions of standard left-handed neutrinos with dark matter without changing the number of effective relativistic degrees of freedom. Using Planck CMB and the WiggleZ galaxy survey $(k\ensuremath{\le}0.12h\text{ }\text{ }{\mathrm{Mpc}}^{\ensuremath{-}1})$ data, we demonstrate that in this model the Hubble tension reduces to approximately $2.1\ensuremath{\sigma}$. Our model predicts potentially observable modifications of the CMB $B$ modes and the matter power spectrum that can be observed in future datasets.

Blind Modulation Identification of Underwater Acoustic MPSK Using Sparse Bayesian Learning and Expectation Maximization

This paper presents a likelihood-based algorithm for identifying different phase shift keying (PSK) modulations, i.e., BPSK, QPSK, and 8PSK. This algorithm selects the modulation type that maximizes a loglikelihood function that is based on the known original constellation associated with the constellation of the received signals for the candidate modulation types. However, there are two problems in non-cooperative underwater acoustic Multiple Phase Shift Keying (MPSK) modulation identification based on the likelihood method. One is the original constellation, which as prior information is unknown. The other is the underwater acoustic multipath channel makes the constellation distort seriously. In this paper, we solved these problems by combining sparse bayesian learning (SBL) with expectation maximization (EM). The specific steps are as follows. Firstly, blind channel equalization can be achieved by channel impulse response (CIR), which is estimated by sparse bayesian learning in single input multi output (SIMO) underwater acoustic channel. Subsequently, we used expectation maximization to compensate amplitude attenuation and phase offset, as the original constellation of MPSK is unknown. Finally, modulation can be successfully identified by the Quasi Hybrid Likelihood Ratio Test (QHLRT). The simulation results show that the channel estimation method based on SBL can eliminate the influence of channel effectively, and the EM algorithm can make the received constellation converge to the preset constellation in the case of unknown original transmit constellation, which effectively solves these two problems. We use the proposed SBL-EM-QHLRT method to achieve an identification rate of more than 95% in underwater acoustic multipath channels with Signal to Noise Ratio (SNR) higher than 15 dB, which provides a new idea for modulation identification of non-cooperative underwater acoustic MPSK.

Feasibility of ultrashort echo time images using full-wave acoustic and thermal modeling for transcranial MRI-guided focused ultrasound (tcMRgFUS) planning

Transcranial MRI-guided focused ultrasound (tcMRgFUS) is increasingly used to non-invasively treat a wide variety of neurological disorders including essential tremors, Parkinson’s disease, and neuropathic pain. Although this treatment is an MRI-guided procedure, the current pre-treatment screening and planning involve a CT of the head to obtain 3D skull images. These images are necessary for estimating the proportion of absorbed energy and the acoustic phase shift associated with the skull and determining the transmit energy of ultrasonic waves to create thermal lesions at a desired focal spot. Ultrashort echo time (UTE) MR sequences can capture signals from tissues such as bone which have a very short transverse relaxation time. In this manuscript, we assess the use of a UTE based sequence to image the calvarium and test the feasibility of obviating the need for CT based imaging during an MR-guided focused ultrasound therapy. We demonstrate that the segmentation of bone using UTE images leads to similar skull density ratio values as determined from CT with high correlation (r = 0.88; p < 0.0001). Furthermore, through treatment specific modeling we demonstrate that the thermal profiles and focal locations are in concordance with the actual treatment plan when using the UTE based skull intensity information suggesting the possibility of replacing the CT scans with UTE based skull imaging in all tcMRgFUS procedures, potentially eliminating unnecessary radiation exposure. Overall, the results indicate that UTE MR imaging may serve as an effective and accurate alternative to CT imaging for both screening and pre-treatment planning on patients undergoing the tcMRgFUS procedure.

Face to Face Collisions of Ion Acoustic Multi-Solitons and Phase Shifts in a Dense Plasma

This work investigates the interactions among ion acoustic (IA) single- and multi-soliton and their corresponding phase shifts in an unmagnetized plasma composed of degenerate electrons, positrons, and positive ions. Two-sided Korteweg-de Vries (KdV) equations are derived by employing the extended Poincare-Lighthill-Kuo (PLK) method for the stretched coordinates. The single- and multi-soliton solutions of the KdV equations are constructed by using the Hirota’s method. The phase shifts are determined for two-, four-, six-, and eight-IA scattering solitons. The effect of positron concentration on electrostatic IA resonances due to the interactions among solitons and their corresponding phase shifts are investigated.

Sound therapy for tinnitus patients

Sound therapy, or use of any sound for the purposes of tinnitus management, is widely accepted as a management tool for tinnitus. Sound therapy have varying goals. Reducing the attention drawn to tinnitus, reducing the loudness of tinnitus, substituting a less disruptive noise. Sound therapy can be achieved with many modalities: Environmental Enrichment, tinnitus maskers, hearing aids and combination instruments such as: Danalogic iFIT Tinnitus, ReSound Live TS, Oticon’s Tinnitus “SoundSupport”, Phonak’s Tinnitus Balance and Widex Zen Fractal Tones. There are other sound devices e.g.: Acoustic Co-ordinated Reset, Neuromodulation, Serenade, Neuromonics, Phase-Out, Phase-shift and tinnitus inhibitory pathway activation. The advantages of sound therapy are: being non-invasive, reduce patient frustration and anxiety, some patients experience residual inhibition and it can facilitate patient’s habituation to tinnitus.

Transmission characteristics of acousto-optic filter using sectioned transducer

Abstract The paper examines operation of a tunable acousto-optic filter applying a sectioned piezoelectric transducer. The analysis was carried out for a tellurium dioxide cell having 1.4-cm long transducer divided into 7 identical sections connected in series. Each section generated acoustic waves with a time delay relatively to adjacent sections. The time delay caused electric and acoustic phase shifts as well as inclination of a resulting acoustic wave front in the crystal. We showed that the inclination of the acoustic front influenced on shape of the filter transmission function causing asymmetry of side lobes. Investigation of the filter was carried out at the driving acoustic frequencies 100–240 MHz. The measurement proved that the electric phase shifts between the adjacent sections increased with the frequency up to 30°. Ratio of intensities of the first two side lobes in the transmission function was varying with the frequency from 0.9 to 0.5. Based on the carried out analysis, we discussed a prototype device using the acoustic beam steering effect. The device applied two sets of transducer sections that simultaneously generated two acoustic wave fronts tilted with respect to each other.

Estimation of low-altitude moving target trajectory using single acoustic array.

An acoustic-signature based method of estimating the flight trajectory of low-altitude flying aircraft that only requires a stationary microphone array is proposed. This method leverages the Doppler shifts of engine sound to estimate the closest point of approach distance, time, and speed. It also leverages the acoustic phase shift over the microphone array to estimate the direction of arrival of the target. Combining these parameters, this algorithm provides a total least square estimate of the target trajectory under the assumption of constant target height, direction, and speed. Analytical bounds of potential performance degradation due to noise are derived and the estimation error caused by signal propagation delay is analyzed, and both are verified with extensive simulation. The proposed algorithm is also validated by processing the data collected in field experiments.

First Detection of the Acoustic Oscillation Phase Shift Expected from the Cosmic Neutrino Background.

The unimpeded relativistic propagation of cosmological neutrinos prior to recombination of the baryon-photon plasma alters gravitational potentials and therefore the details of the time-dependent gravitational driving of acoustic oscillations. We report here a first detection of the resulting shifts in the temporal phase of the oscillations, which we infer from their signature in the cosmic microwave background temperature power spectrum.

Phase shifts in binaural stimuli provide directional cues for sound localisation in the field cricket Gryllus bimaculatus.

The cricket's auditory system is a highly directional pressure difference receiver whose function is hypothesised to depend on phase relationships between the sound waves propagating through the auditory trachea that connects the left and right hearing organs. We tested this hypothesis by measuring the effect of experimentally constructed phase shifts in acoustic stimuli on phonotactic behavior of Gryllus bimaculatus, the oscillatory response patterns of the tympanic membrane, and the activity of the auditory afferents. The same artificial calling song was played simultaneously at the left and right sides of the cricket, but one sound pattern was shifted in phase by 90 deg (carrier frequencies between 3.6 and 5.4 kHz). All three levels of auditory processing are sensitive to experimentally induced acoustic phase shifts, and the response characteristics are dependent on the carrier frequency of the sound stimulus. At lower frequencies, crickets steered away from the sound leading in phase, while tympanic membrane vibrations and auditory afferent responses were smaller when the ipsilateral sound was leading. In contrast, opposite responses were observed at higher frequencies in all three levels of auditory processing. Minimal responses occurred near the carrier frequency of the cricket's calling song, suggesting a stability at this frequency. Our results indicate that crickets may use directional cues arising from phase shifts in acoustic signals for sound localisation, and that the response properties of pressure difference receivers may be analysed with phase-shifted sound stimuli to further our understanding of how insect auditory systems are adapted for directional processing.

Surface acoustic wave driven ferromagnetic resonance in nickel thin films: Theory and experiment

We present an extensive experimental and theoretical study of surface acoustic wave-driven ferromagnetic resonance. In a first modeling approach based on the Landau-Lifshitz-Gilbert equation, we derive expressions for the magnetization dynamics upon magnetoelastic driving that are used to calculate the absorbed microwave power upon magnetic resonance as well as the spin current density generated by the precessing magnetization in the vicinity of a ferromagnet/normal metal interface. In a second modeling approach, we deal with the backaction of the magnetization dynamics on the elastic wave by solving the elastic wave equation and the Landau-Lifshitz-Gilbert equation selfconsistently, obtaining analytical solutions for the acoustic wave phase shift and attenuation. We compare both modeling approaches with the complex forward transmission of a LiNbO$_3$/Ni surface acoustic wave hybrid device recorded experimentally as a function of the external magnetic field orientation and magnitude, rotating the field within three different planes and employing three different surface acoustic wave frequencies. We find quantitative agreement of the experimentally observed power absorption and surface acoustic wave phase shift with our modeling predictions using one set of parameters for all field configurations and frequencies.

On the Power Spectra of Sound Transmitted through Turbulence

The power spectrum of sound received from a known acoustic source after transmission through a region of turbulence is calculated by a convolution with a distortion function. The latter specifies the modification of the acoustic power spectrum as it propagates through the turbulent region. The distortion function is the Fourier transform with regard to time of the characteristic function of a bivariate aleatory process, whose random variables are the acoustic phase shifts of two neighbouring waves; the phase shifts are due to the Doppler effect of the random turbulence velocity and are a function of position and time. The turbulence spectrum is used to calculate the r.m.s. phase shift and also the correlation time in the correlation coefficient. This specifies the received power spectrum for any type of source, viz a monochromatic or tonal source, or a broadband source, e.g. Gaussian or exponential. The received power spectra depend on the choice of correlation function, e.g. Gaussian or volume conserving. The received power spectra simplify in the asymptotic case of large r.m.s. phase shift; otherwise, the exact received power spectra consists of an attenuated source spectrum plus a series of scattering broadbands. The latter demonstrate how the acoustic energy in the emitted source spectrum is spread over a wider range of frequencies by propagation through turbulence, leading to spectral broadening in the received spectrum.

Acoustic phase shift: Objective evidence for intralabyrinthine pressure disturbance in Menière's disease provided by otoacoustic emissions

Still today, Menière's disease (MD) can be definitively diagnosed only on post-mortem findings of endolymphatic hydrops. Otoacoustic emission (OAE) phase has been shown to be highly sensitive to intracranial pressure. Preliminary analysis of OAEs in MD patients indicated high sensitivity to slight variations in intracranial pressure. The principal objective of the present study was to confirm this specific sensitivity of OAEs in MD. In a prospective study of 32 consecutive cases of acute MD seen in consultation or hospital, 20 patients (23 ears) underwent acoustic phase-shift test: i.e., seated vs. supine OAE phase centered around 1kHz, with results compared to controls. The acoustic phase-shift test was performed in 62.5% of acute patients (58.9% of affected ears). In the control group, the 95% confidence interval for phase shift was between -30° and +45°. Phase shift was significantly elevated, beyond the normal interval, in 18 of the MD patients: range, -80° to +145°. Sensitivity was 90%. Overall, in patients in whom transient evoked OAEs (TEOAEs) were present, positive predictive value was 100% and negative predictive value 92.3%. The acoustic phase-shift test proved useful and powerful in demonstrating pressure imbalance in acute Menière's disease.

Response time of thermal flow sensors with air as fluid

Due to their fast response time miniaturized thermal flow sensors can be applied well for the measurement of instationary gas flow. For some applications, the response time of the sensor must be known with high accuracy. We investigated three methods for response time determination with air: a jump of temperature induced by electric heating, a gas velocity step made by a membrane burst and acoustic phase shifts between sound velocity and sound pressure (standing and traveling waves). The measurements have shown that the response time of thermal flow sensors is a function of flow velocity. For stagnant flow, the thermal response time is about 4.5ms for our thermal flow sensors. With increasing flow from the heater to the thermopiles, the heat transfer rises. Thus, the response time is faster and decreases to about 1ms.

Coupling High-Resolution Acoustic Sensor Measurements with Analytical and Numerical Porous Media Solute Transport Modeling

This paper presents the development of a novel acoustic sensor that enhances Doppler approaches to monitor groundwater vector flow. The technique is based on a high-resolution acoustic phase measurement: flowing water introduces a shift in the acoustic velocity component between the transmitter and receiver. By switching the transmitter and receiver modes at periodic intervals, the resulting magnitude of the acoustic phase shift yields the speed of water flow. The high-resolution of the measurement comes from the feedback loop architecture that forces an output toneburst to the transmitter to remain in quadrature with the signal recorded at the receiver. Flow velocity measurements in a column filled with saturated sand (subjected to salt tracer injections), were validated in an ASTM standard constant-head hydraulic test column. Several analytical solution solute transport models and a finite-element numerical model were applied to the test column and compared with measured data. Model predictions obtained before the actual experiments were conducted were very useful to determine expected salt breakthrough curves. The models were subsequently calibrated after the laboratory data were recorded. Results presented clearly indicate the importance of selecting models that incorporate appropriate boundary conditions.

Response time of thermal flow sensors

Thermal flow sensors are applied for measurement of instationary flow and for the control of dispensing very small fluid volumes. For these applications, the response time of the sensor must be determined accurately. We investigated three methods for response time determination: a jump of temperature induced by electric heating, a gas velocity step made by a membrane burst and acoustic phase shifts between sound velocity and sound pressure. The measurements have shown that the response time of thermal flow sensors is a function of flow velocity. For stagnant flow, the thermal response time is at about 4.5 ms. With increasing flow, heat transfer rises, thus response time is faster and moves down to about 1 ms.

Film mechanical resonance phenomenon during electrochemical deposition of polyaniline

Crystal admittance measurements during potentiodynamic electrodeposition from aqueous HCl of polyaniline films on a thickness shear mode resonator show the phenomenon of film resonance. This special situation arises when the combination of materials properties (film shear modulus and density) and sample nature (film thickness) is such that the acoustic phase shift across the film, φ = π/2 radians. Admittance spectra in the acoustically thick (but pre-film resonance) region were fitted to a standard Butterworth van Dyke (BvD) electrical equivalent circuit (with series L, C, and R elements) to yield film storage and loss shear moduli. From these values, it was possible to calculate φ of the growing film and thereby track the onset of film resonance. As φ approached π/2 radians, the admittance peak rapidly shifted to higher frequencies and changed dramatically in amplitude. An electrical equivalent circuit with parallel L, C, and R elements was used to model film resonance data; this simplified model ignores the contribution of the bathing electrolyte. Agreement of film shear moduli from both models, and of resonant film thickness from the parallel element equivalent circuit model and coulometric extrapolation of pre-resonant responses, supports the basic tenets of the film resonance model. At film resonance, the cyclic voltammetric response changed dramatically; it is speculated that this is a consequence of the unusual polymer dynamics at film resonance.