Acoustic Interferometer Research Articles

Bound states in the continuum and topological phase singularities in an acoustic Gires-Tournois interferometer setting

Bound states in the continuum and topological phase singularities in an acoustic Gires-Tournois interferometer setting

Coupled Resonator Acoustic Waveguides‐Based Acoustic Interferometers Designed within 2D Phononic Crystals: Experiment and Theory

AbstractThe acoustic response of defect‐based acoustic interferometer‐like designs, known as Coupled Resonator Acoustic Waveguides (CRAWs), in 2D phononic crystals (PnCs) is reported. The PnC is composed of steel cylinders arranged in a square lattice within a water matrix with defects induced by selectively removing cylinders to create Mach‐Zehnder‐like (MZ) defect‐based interferometers. Two defect‐based acoustic interferometers of MZ‐type are fabricated, one with arms oriented horizontally and another one with arms oriented diagonally, and their transmission features are experimentally characterized using ultrasonic spectroscopy. The experimental data are compared with finite element method (FEM) simulations and with tight‐binding (TB) calculations in which each defect is treated as a resonator coupled to its neighboring ones. Significantly, the results exhibit excellent agreement indicating the reliability of the proposed approach. This comprehensive match is of paramount importance for accurately predicting and optimizing resonant modes supported by defect arrays, thus enabling the tailoring of phononic structures and defect‐based waveguides to meet specific requirements. This successful implementation of FEM and TB calculations in investigating CRAWs systems within PnCs paves the way for designing advanced acoustic devices with desired functionalities for various practical applications, demonstrating the application of solid‐state electronics principles to underwater acoustic devices description.

Determination of the Acoustic Wave Velocity and Attenuation in Liquids with Different Acoustic Impedances Using an Acoustic Interferometer

Determination of the Acoustic Wave Velocity and Attenuation in Liquids with Different Acoustic Impedances Using an Acoustic Interferometer

Acoustic Michelson interferometer based on a phononic crystal

A practical and highly sensitive acoustic Michelson interferometer with a small form factor is introduced. It involves two different types of phononic crystals composed of steel rods in water acting as a medium for self-collimated waves and mirrors for the reference and sample beams, as well as a beam splitter formed by modified scatterers arranged diagonally. Finite-element method simulations are employed to demonstrate its operation around 200 kHz. Equifrequency contour analysis reveals self-collimation of ultrasonic waves between 190 and 210 kHz. Introduction of the beam splitter and mirror phononic crystals is not detrimental to self-collimation where outgoing waves from the two interferometer arms interfere such that the output intensity varies in a cosine squared manner. Consequently, maximum sensitivity is achieved when the movable mirror displacement is either zero or half of the interferometer phononic crystal period. On small intervals in these ranges, micrometer-scale displacement resolution is achievable, as the output intensity drops by 0.2% per micrometer. Thus, displacements smaller than a percent of the wavelength are easily resolvable. Nanoscale resolution can be obtained with a scaled down interferometer design. Moreover, application to liquid concentration sensing by considering ethanol–water binary mixture is demonstrated. A percent increase in weight fraction of ethanol up to 10% in the mixture leads to an intensity drop as high as 2%. Thus, significantly higher sensitivities compared to sensing schemes based on resonance frequency shift are attainable. The proposed approach can be adapted for surface acoustic waves in strain measurement or biosensing.

Determination of the Acoustic Wave Velocity and Attenuation in Liquids with Different Acoustic Impedances Using an Acoustic Interferometer

Theoretical and experimental features of using an acoustic interferometer for determining the velocity and attenuation of an acoustic wave in liquids with different acoustic impedances are studied. It is shown for the first time that the indicated impedance determines the ratio of the resonance values of the maximum and minimum transmission coefficient S12 for the same transmitter–receiver pair on the dependence of the transmission coefficient on the distance between the transducers. A methodology has been developed for determining the wave attenuation of a liquid free from the influence of “apparent” attenuation associated with the loss of part of the acoustic power to the transducers.

Vertical Surface Phononic Mach-Zehnder Interferometer

In this work, we propose and explore a double-stage phononic crystal (PnC) consisting of a top suspended $\mathrm{ZnO}$ layer, an array of sandwiched $\mathrm{Si}$ pillars, and a bottom $\mathrm{ZnO}$ layer on a $\mathrm{Si}$ substrate. The proposed double-stage PnC exhibits interesting behavior of routing the incident surface acoustic waves (SAWs) based on polarization and frequency, so that it can be considered as an efficient building block for alternative multistage SAW components. Here, we design the double-stage PnC to behave as an efficient vertical SAW splitter in a Mach-Zehnder interferometer, using the excitation of appropriate surface-coupled modes through the periodic locally resonating pillars. Benefiting from the acoustoelectric effect in $\mathrm{ZnO}$, the exposed top $\mathrm{ZnO}$ layer serves as the sensing branch, and the bottom $\mathrm{ZnO}$ layer serves as the reference branch in the presented vertical Mach-Zehnder interferometer. The vertical configuration of the proposed design allows exposure of the top $\mathrm{ZnO}$ layer to external stimulations, such as exposure to ultraviolet illumination or a hydrogen environment, while protecting the underlying parts from being exposed. This structural aspect simplifies the experimental implementation of our design in comparison with the conventional planar Mach-Zehnder interferometers by avoiding the necessity of in-plane focusing of external stimulation on the sensing branch. Our optimized Mach-Zehnder interferometer shows an output transmission signal of \ensuremath{-}8 dB and a high extinction ratio of 23 dB at 8.6 GHz when the conductivity of the top $\mathrm{ZnO}$ layer is increased from about 1 S/m to 100 S/m via external stimulation. Here, we propose a highly sensitive miniature vertical surface acoustic Mach-Zehnder interferometer, which may open up alternative horizons for future multistage SAW components.

Thermal Modulation of Gigahertz Surface Acoustic Waves on Lithium Niobate

Surface acoustic wave (SAW) devices have wide range of applications in microwave signal processing. Microwave SAW components benefit from higher quality factors and much smaller crosstalk when compared to their electromagnetic counterparts. Efficient routing and modulation of SAWs are essential for building large-scale and versatile acoustic-wave circuits. Here, we demonstrate integrated thermo-acoustic modulators using two SAW platforms: bulk lithium niobate and thin-film lithium niobate on sapphire. In both approaches, the gigahertz-frequency SAWs are routed by integrated acoustic waveguides while on-chip microheaters are used to locally change the temperature and thus control the phase of SAW. Using this approach, we achieved phase changes of over 720 degrees with the responsibility of 2.6 deg/mW for bulk lithium niobate and 0.52 deg/mW for lithium niobate on sapphire. Furthermore, we demonstrated amplitude modulation of SAWs using acoustic Mach Zehnder interferometers. Our thermo-acoustic modulators can enable reconfigurable acoustic signal processing for next generation wireless communications and microwave systems.

Multi-cavity gravito-acoustic oscillation modes in stars

Context. Over recent decades, asteroseismology has proven to be a powerful method for probing stellar interiors. Analytical descriptions of the global oscillation modes, in combination with pulsation codes, have provided valuable help in processing and interpreting the large amount of seismic data collected, for instance, by space-borne missions CoRoT, Kepler, and TESS. These prior results have paved the way to more in-depth analyses of the oscillation spectra of stars in order to delve into subtle properties of their interiors. This purpose conversely requires innovative theoretical descriptions of stellar oscillations. Aims. In this paper, we aim to analytically express the resonance condition of the adiabatic oscillation modes of spherical stars in a very general way that is applicable at different evolutionary stages. Methods. In the present formulation, a star is represented as an acoustic interferometer composed of a multitude of resonant cavities where waves can propagate and the short-wavelength JWKB approximation is met. Each cavity is separated from the adjacent ones by barriers, which correspond to regions either where waves are evanescent or where the JWKB approximation fails. Each barrier is associated with a reflection and transmission coefficient. The stationary modes are then computed using two different physical representations: (1) studying the infinite-time reflections and transmissions of a wave energy ray through the ensemble of cavities or (2) solving the linear boundary value problem using the progressive matching of the wave function from one barrier to the adjacent one between the core and surface. Results. Both physical pictures provide the same resonance condition, which ultimately turns out to depend on a number of parameters: the reflection and transmission phase lags introduced by each barrier, the coupling factor associated with each barrier, and the wave number integral over each resonant cavity. Using such a formulation, we can retrieve, in a practical way, the usual forms derived in previous works in the case of mixed modes with two or three cavities coupled though evanescent barriers, low- and large-amplitude glitches, and the simultaneous presence of evanescent regions and glitches. Conclusions. The resonance condition obtained in this work provides a new tool that is useful in predicting the oscillation spectra of stars and interpreting seismic observations at different evolutionary stages in a simple way. Practical applications require more detailed analyses to make the link between the reflection-transmission parameters and the internal structure. These aspects will be the subject of a future paper.

Multi-dimensional wave steering with higher-order topological phononic crystal

The recent discovery and realizations of higher-order topological insulators enrich the fundamental studies on topological phases. Here, we report three-dimensional (3D) wave-steering capabilities enabled by topological boundary states at three different orders in a 3D phononic crystal with nontrivial bulk topology originated from the synergy of mirror symmetry of the unit cell and a non-symmorphic glide symmetry of the lattice. The multitude of topological states brings diverse possibilities of wave manipulations. Through judicious engineering of the boundary modes, we experimentally demonstrate two functionalities at different dimensions: 2D negative refraction of sound wave enabled by a first-order topological surface state with negative dispersion, and a 3D acoustic interferometer leveraging on second-order topological hinge states. Our work showcases that topological modes at different orders promise diverse wave steering applications across different dimensions.

Double Mach–Zehnder acoustic emission interferometer for detection of damage in structures

The work described in this article pertains to the development of a modified Mach–Zehnder double interferometer for multi-source detection of high frequency acoustic emission signals. The proposed modified double interferometer is capable of detecting acoustic emissions with central frequencies within the MHz spectral range applicable for detection of microcracks in welded and bolted joints of steel structures such as in bridges. The location detection accuracy of the modified double interferometer is 2 meters, which is markedly more precise than the existing Mach–Zehnder interferometers at 20 meters. In compare to phase shifted FBGs, the proposed modified interferometer is capable of detecting higher frequency acoustic emission signals. Proof of concept experiments were conducted on an arch steel bridge in the laboratory, in which high frequency acoustic emissions simulating damage were created by breakage of pencil leads and detected by the modified double interferometer.

Prediction of sound insulation of flexible panels in low frequencies with dynamics and volume relations

The problem of sound insulation in the low-frequency region (up to 100 Hz) is relevant, but little has been studied theoretically and practically has not been investigated experimentally due to the lack of the necessary experimental base. Especially important is the solution of the problem for local isolation of low-frequency mechanisms by perspective mesh-plate flexible panels (MPP) for various configurations of isolated and protected volumes and at low first natural frequencies. The purpose of this study is to evaluate the effect of forced vibration panel and room volume ratio of the source of the perturbation and the protected volume. The objective is to develop a mathematical model, which can verify the adequacy of the experimental results obtained at frequencies above 30 Hz and acoustic reverberation chambers interferometer. As a result, a formula for calculating the sound insulation has been received, allowing taking into account the volume ratio of the shared spaces and the transition through resonance. The results of the research can be used in the design of direct soundproofing of low-speed mechanisms or for the organization of the first stage of soundproofing and modernization of the design of the MPP in relation to specific conditions and requirements for sound insulation.

Bispectrum as baryon acoustic oscillation interferometer

The galaxy bispectrum, measuring excess clustering of galaxy triplets, offers a probe of dark energy via baryon acoustic oscillations (BAOs). However up to now it has been severely underused due to the combinatorically explosive number of triangles. Here we exploit interference in the bispectrum to identify triangles that amplify BAOs. This approach reduces the computational cost of estimating covariance matrices, offers an improvement in BAO constraints equivalent to lengthening BOSS by 30%, and simplifies adding bispectrum BAO information to future large-scale redshift survey analyses.

NFLUENCE OF BIOACOUSTIC STIMULATION OF THE RESPIRATORY SYSTEM OF SPORTSMEN ON LIFE-CAPACITY OF LUNGS

Purpose. To study the influence of bioacoustic stimulation of the respiratory system in athletes on the value of vital capacity of the lungs.Materials and methods. For technical realization of bioacoustics stimulation of the respiratory system, a biotechnical system, containing a block of an acoustic interferometer, an interferometer control system, and a system for recording sound field parameters, was used. The study involved nine athletes test volunteers: men aged 19 to 31 years, a sport – skiing, a sports category – the first adult, who underwent a training using bioacoustics stimulation in the following way: three times for three minutes each exposure, with an interval between exposures equal to one minute. Before the beginning of each exposure, the medical staff conducted a survey of the athlete’s well-being, measurement of the heart rate and blood saturation with oxygen, and determination of the vital capacity of the lungs. During the exposure, a constant control of health, heart rate and blood saturation with oxygen was conducted, and measurements of the vital capacity of the lungs were carried out after each stimulating effect.Results. Eight of the nine volunteers increased the vital capacity of the lungs, according to subjective sensations, all volunteers noted a feeling of deeper breaths after exposure, a feeling of lightness of breath and absence of shortness of breath after training afterwards. Athletes who participated in earlier stages of the study noted that the effect of stimulation is pronounced in terms of subjective assessments of a feeling of lightness of breath, a greater depth of inspiration, a greater volume of breathing at once, and within 3 days after three-fold exposure during one session. Conclusion. The results of the study testify to the significant potential possibilities of bioacoustics stimulation of the respiratory system of athletes to increase the functional reserves of the body, determined by the increase in the vital capacity of the lungs. Important for the practice of sports medicine is that the increase in vital capacity of the lungs occurs after a one-day course of bioacoustics stimulation of the respiratory system, persists for 3 or more days after stimulation and is accompanied by subjective estimates of easier breathing.

Using a High-Quality Thermostated Acoustic Interferometer to Study Changes in the Structure of Human Serum Proteins

An acoustic interferometric technique for determining the protein in blood serum is presented. This acoustic approach is based on high-precision measurements of the temperature dependences of the velocity, frequency, and absorption of ultrasound. The acoustic characteristics of blood serum are measured by a constant-length interferometer in acoustic wells with volumes of around 80 μL in the temperature range of 28–40°C and the frequency range of 1.4–14 MHz.

An improved non-contact thermometer and hygrometer with rapid response

Previously (Underwood et al 2015 Meteorol. Appl. 22 830) we reported first tests of a device capable of simultaneous, non-contact, temperature and humidity (NCTAH) measurements in air. The device used an acoustic thermometer and a tuneable diode laser absorption spectrometer (TDLAS), a combination which should be capable of an extremely rapid response to changes in humidity as it does not require moisture in a solid-state matrix to equilibrate with the surrounding air. In this paper we report recent developments of the instrument focussed on reducing its response time so that it can be used as a reference instrument for assessing the response time of conventional humidity sensors. In addition, the interdependence of the temperature and humidity estimates is now accounted for in real-time using an iterative procedure, which eliminates the need for data post-processing.The TDLAS measures water molecule number density based on the transmission of an infrared beam (approximate wavelength 1360 nm) through a 0.6 m path length. The acoustic thermometer is based around a fixed-path acoustic interferometer. The improved NCTAH device now produces estimates of the water molecule number density every 20 ms and the temperature output displays an RC filter-like response, with a time constant of approximately 30 ms.The instrument has been tested in a climatic chamber through a temperature range of −40 °C to +40 °C and a dew point range of −43 °C to +38 °C, at atmospheric pressure, comparing the instrument readings with those from a calibrated hygrometer and four platinum resistance thermometers. In steady-state conditions, the instrument readings are in good agreement with the conventional sensors, with temperature differences less than 1 °C (repeatability 0.1 °C), and humidity differences mostly within 5% of mixing ratio. Under transient conditions, we demonstrate how the instrument can be used to evaluate the response times of conventional sensors.

Acoustic beam splitting at low GHz frequencies in a defect-free phononic crystal

The directional waveguiding in a 2D phononic crystal is simulated based on the analysis of equifrequency contours. This approach is utilized to investigate acoustic beam splitting in a defect-free nanostructure in the low GHz range. We find relaxed limitations regarding the source parameters compared to similar approaches in the sonic regime. Finally, we discuss the possibility to design an acoustic interferometer device at the nanoscale at GHz frequencies.

Research on the Combination of Underwater Acoustic Countermeasure Equipments Against Torpedo

Today the use of acoustic countermeasure equipment has become the main means in submarine defense torpedo operation. Combination of acoustic countermeasure equipments are used during the operation so that we can amplify the countermeasure effect. Based on the subject of the acoustic countermeasure equipments’ combined use, this paper analyses the interference between these soft kill countermeasure equipments including gas curtain, acoustic decoy and acoustic interferometer, summarizes the advantages and disadvantages of the different combined use of acoustic countermeasure equipments.

A combined non‐contact acoustic thermometer and infrared hygrometer for atmospheric measurements

ABSTRACTTemperature and humidity measurements in the upper atmosphere are of critical importance for understanding the Earth's climate. However, such measurements are difficult for several reasons. Rising sondes carry moisture upwards, compromising measurements in the dry stratospheric environment. In addition, the difference in the time constants of thermometers and hygrometers leads to difficulties in determining the extent of saturation of the air. Finally, the effects of insolation, evaporative cooling and the poor thermal contact with the air compound the other measurement problems.To address these issues, tests on a new non‐contact temperature and humidity sensor (non‐contact thermometer and hygrometer, NCTAH), which can make rapid non‐contact measurements in atmospheric air, have been reported.The temperature and humidity measurements are made using an acoustic interferometer and a tuneable diode laser absorption spectrometer (TDLAS), respectively. This combination of sensors offers many potential advantages and allows each sensor to supply a key correction required by the other. The present study describes the design rationale and reports test results measured at the National Physical Laboratory and results from simulated ascents through the atmosphere (to −57 °C and 130 hPa characteristic of an altitude of 15 km) at the Planetary Environment Facility at the University of Aarhus, Denmark.The NCTAH makes two temperature measurements per second with a resolution of ∼0.01 °C and a likely uncertainty of measurement of u(k = 1) = 0.1 °C. Water vapour mixing ratios were measured over a range of ∼100 to 3 x 104 ppmv corresponding to dew points from −42 to +24 °C at atmospheric pressure.

The compressibility of CaCO3–Li2CO3–Na2CO3–K2CO3 liquids: application to natrocarbonatite and CO2-bearing nephelinite liquids from Oldoinyo Lengai

To constrain the compressibility of natrocarbonate liquids, sound-speed measurements were made on 11 liquids in the CaCO3–Li2CO3–Na2CO3–K2CO3 quaternary system from 808 to 1323 K at 1 bar with a frequency-sweep acoustic interferometer. CaCO3 concentrations range from 15 to 50 mol% in four of the experimental liquids. The sound-speed data for all liquids were converted to isothermal compressibility (β T ), which were fit to an ideal mixing model with respect to composition; the average residual is 1.2 %. Fitted values (±1σ) of the partial molar compressibility (10−2 GPa−1) at 1100 K were derived for CaCO3 (5.36 ± 0.13), Li2CO3 (8.09 ± 0.06), Na2CO3 (10.62 ± 0.07), and K2CO3 (14.09 ± 0.06); these values translate to bulk modulus values of 18.7, 12.4, 9.4, and 7.1 GPa, respectively, reflecting the relatively large compressibility of carbonate liquids. The data are additionally used to estimate the partial molar volume and compressibility of the CO2 component dissolved as carbonate in nephelinite liquids; the density of this dissolved component at 1423 K and 1 GPa ranges from 1.62, 1.71 to 1.83 g/cm3 when it is complexed with K+, Na+, and Ca2+, respectively, and is estimated to be ~2.05 and 2.14 g/cm3 when complexed with Fe2+ and Mg2+, respectively. The results from this study can be applied to natrocarbonate liquids, such as those erupted from Oldoinyo Lengai volcano in Africa, and indicate a melt density of ~2.19 g/cm3 at 1150 °C and 1 GPa, which is ~18 % less dense than the average melt density (~2.67 g/cm3) calculated for associated Mg-poor nephelinite liquids at the same conditions and volatile-free. However, the dissolution of 10.1 wt% H2O and 8.7 wt% CO2 in the average nephelinite melt (based on volatile contents reported in the literature for these magmas) reduces its density to ~2.14 g/cm3 at 1150 °C and 1 GPa, eliminating the buoyancy contrast with the natrocarbonate melt. In turn, it is highly likely that the natrocarbonatite melts contained significant amounts of dissolved H2O and, as an example, the addition of 10 wt% H2O lowers the melt density by ~14 % to ~1.88 g/cm3, and therefore re-establishes a large density contrast with the volatile-rich nephelinite melts.

Acoustic radiation force and particle dynamics in cylindrical resonators

Acoustic radiation force is widely used in biomedical studies and medical diagnostics. Among the promising areas of its application is concentration and stirring of particles and bubbles in ultrasonic resonators (e.g., [1]). In a number of cases, cylindrical resonators have a practical advantage vs. plane resonators (acoustic interferometers) due to the axial energy concentration [2], [3]. Theoretical analysis of particle dynamics in such resonators is often very complicated. This presentation outlines recent results in modeling of dynamics of micro-particles and microbubbles in cylindrical resonators. In particular, concentration and separation of “heavy” and “light” particles and near-resonant bubbles are discussed. The role of ultrasound nonlinearity in the considered effects is also discussed. [1]. A. Sarvazyan and L. Ostrovsky, J. Acoust. Soc. Am. 125, 3548–3554 (2009). [2]. A. Priev and A. Sarvazyan, J. Acoust. Soc. Am. 125, 2593 (2009). [3]. L. Ostrovsky, A. Priev, V. Ponomarev, and Y. Barenholz, P...