Acoustic Reflection Research Articles

Graphene Solution‐Gated Field‐Effect Transistor for Ultrasound‐Based Wireless and Battery‐Free Biosensing

AbstractThe development of wireless and battery‐free sensors for biomedical applications is a fast growing research and industrial field. It promises to greatly improve the patient's comfort during the diagnosis phase, but also in the treatment of chronic diseases. While the standard technologies are based so far on electromagnetic waves, ultrasonic powering and communication is offering perspectives to further reduce the size of the sensor in order to develop minimally invasive electronic implants. Wireless and battery‐free ultrasound‐based devices for healthcare monitoring comprise a piezoelectric element for the powering and communication, and a variable shunt load that varies according to a physiological parameter of interest. The changes in the load modify the acoustic reflectivity of the piezoelectric element, which can be detected using a pulse‐echo protocol. In the present study, the use of graphene solution‐gated field‐effect transistor is introduced as a new type of shunt load. Using an mm‐sized device, it is shown that the amplitude of an ultrasonic wave that reflects on the piezoelectric component is modulated by the voltage applied on the gate of the transistor both in physiological medium and biological tissue. This study sets the basis toward a new type of ultrasound‐based wireless and battery‐free biosensors.

Acoustic Waves Reflection from a Layer of a Multifractional Polydispersed Gas–Droplet Mixture

Acoustic Waves Reflection from a Layer of a Multifractional Polydispersed Gas–Droplet Mixture

English

In this study, various materials like ZnO, PZT, BaTiO3, and LiNbO3 for piezoelectric thin-film are used to simulate Solidly Mounted Resonators (SMR). These materials have unique material characteristics that make them suitable for a specific application. High Q Factors are needed in communication systems for low noise and extremely sensitive signals. For the purpose of raising the SMR resonator's Q Factor, the various piezoelectric materials are examined. It is investigated how an SMR performs in connection to the stages of the Bragg reflector configuration and its constituent parts. Layers having low and high acoustic impedances, including SiO2/AlN, SiO2/W, SiO2/Mo, SiO2/ZnO and SiO2/Ta2O5, make up Bragg's reflector design. A comprehensive investigation of flexible SMR was conducted using COMSOL Multiphysics element method (FEM) simulations. The implications of the building phases and material used to make Bragg's reflectors on the functionality of the flexible SMR are thoroughly analyzed. Multiple Bragg's reflector designs' comparative results have been gathered and reported. W/SiO2-based Bragg's reflector topologies have been discovered in the most recent research with ZnO and are most suited to offer increased coupling coefficient and Quality Factor performance. It was found that 0.2 um, 0.3 um, and 0.1 um, respectively, were the best-optimized thicknesses for top metal electrodes, the piezoelectric layer, and the low and high acoustic impedance brag reflector layers. The current study's findings demonstrate that the simulated values of the coupling coefficient (Keff2 ) and quality factor (Q) for the optimal dimension of the SMR structure are 0.09117 (or 9.117%) and 2335, respectively.

Experimental investigation of propeller noise in ground effect

The aerodynamic propeller performance and aeroacoustic characteristics of a single two-bladed propeller subjected to Ground Effect are investigated using experiments in an anechoic chamber. A strong increase in thrust, torque and power coefficients when a propeller operates in Ground Effect is demonstrated, consistent with previous studies. A low-fidelity Blade Element Momentum Theory model adapted for Ground Effect is implemented to cross-validate the aerodynamic results. The near-field and far-field spectra and their coherence are studied for various propeller distances from the ground plane and compared with the isolated case. The far-field noise measurements indicate that additional tonal peaks appear with the introduction of the ground plane when compared to isolated configuration. While in-Ground Effect, additional high-frequency broadband humps are observed at some polar angles not seen in isolated configuration. Two discrete regions, a shielded and reflection zone, with respective reduction and enhancement of the Overall Sound Pressure levels are observed. The primary reason for noise increase within the reflection zone is a result of pure acoustic reflection from the ground surface. The near-field measurements from an array of embedded high-response microphones in the ground plane indicate that the main source of the propeller noise is in the tip region. Near-field measurements reconfirm flow results from literature with near-field and far-field acoustic results. The present study may find important practical applications within Urban Air Mobility (UAM), especially in the design of vertiport landing pads and propellers for effective noise mitigation, aerodynamic performance, and prediction during the vertical take-off and landing phases of flight.

Denoising method of borehole acoustic reflection image using convolutional neural network

Using a small remote reflection wave, the borehole acoustic reflection imaging obtains high-resolution images from tens of meters away. Even after elimination, the direct mode wave excited near the borehole significantly contaminates the usable reflection wave, which then translates to solid noise in the migratory image. The severe noise significantly obstructs the application of the technique. The paper considers the use of a convolutional neural network for the primary data that we find most useful and treats the migration result as a type of digital image. We create a substantial dataset of simulated images using the Born approximation and the Kirchhoff migration method; we build a large-simulation image dataset. The designed multiscale recursive residual network leverages three branches to extract features at multiple resolutions. The learned multiscale features are recalibrated by the Double Attention Unit, and then aggregated by the Selective Kernel Feature Fusion module, preserving spatial details and extracting enriched contextual information. The network is trained on the simulated dataset using the MSE loss function and achieves higher accuracy in processing test images, compared with the widely-used DnCNN, demonstrating its effectiveness. The trained network is then applied directly to the real field image, where it successfully removes background noise while preserves the edges of valuable reflectors, proving the robustness and validity of the proposed methods.

Measurement of the acoustic reflectance function based on Lamb wave using high f-number transducers

Ultrasonic reflectivity using a V(z) technique is a powerful characterization method in acoustic microscopy to measure the elastic properties of materials. Conventional techniques generally use a low f-number with high frequency; however, to measure the reflectance function of the highly attenuative material, a low frequency is essential. In this study, the transducer-pair method based on Lamb waves is used to measure the reflectance function of a highly attenuative material. The results demonstrate the feasibility of the proposed method using a commercial ultrasound transducer with high f-number.

Nonlinear dynamics of pure intrinsic thermo-acoustic modes

In this paper the nonlinear dynamics of the pure Intrinsic Thermo-Acoustic (ITA) modes are experimentally investigated for burner stabilized premixed flames by decoupling them from the acoustic modes. Thereto, a setup is used with up- and downstream mufflers that provide close to anechoic boundary conditions. This enables the investigation of the self-excited oscillations of the flame, without the influences of acoustic reflections. An experimental bifurcation analysis is conducted to systematically investigate the different asymptotic oscillatory states and their transitions. By increasing the upstream velocity, the flame looses stability through a supercritical Hopf bifurcation and reveals limit cycles with a single dominant frequency. For increasing upstream velocity, a low frequent mode appears, resulting in quasi-periodic oscillations. This regime is characterized by a beating phenomenon with simultaneous amplitude and frequency modulations. When the upstream velocity is even further increased, a period doubling bifurcation is observed. To our best knowledge, the experimental investigation of the nonlinear dynamical behavior of pure ITA modes and, in particular, the low frequency oscillation, has not been reported before, and it provides valuable insights towards developing accurate time-domain models of the nonlinear acoustic behavior of premixed flames. Finally, a phenomenological model of two coupled oscillators is introduced that is able to qualitatively reproduce all observed nonlinear oscillations of the flames.

Fiberboard made from scrap denim: Characterization of its properties by effective bulk modulus elastography

Fiberboards from scrap denim were fabricated using two different resins, melamine urea formaldehyde (MUF) and polymeric methylene diphenyl diisocyanate (pMDI). Resin content and MUF-pMDI weight ratio were studied. Physical and mechanical tests determined the modulus of elasticity (MOE), modulus of rupture (MOR), internal bond (IB), thickness swell (TS), and water absorption (WA). The resin content had significant impact on all properties. The MOE and IB were affected by the MUF-pMDI ratio. With 17 wt% more pMDI resin portion in the core layer of the denim boards, the IB for the denim fiberboard with a resin content of 15% was enhanced by 306%, while by 205% for the resin content of 25%. The increase in pMDI portion in the core layer of the boards improved both TS and WA of the scrap denim fiberboard. Effective bulk modulus elastography (EBME) was used to measure the acoustic reflection for the estimation of the strength properties of the denim fiberboard. The modulus results from EBME were correlated to the MOR, MOE, and IB of the denim fiberboard. A high correlation was found between the modulus from EBME and IB (R2 > 0.98). EBME can be a great technique to evaluate the bulk modulus distribution of the composites.

Acoustic compact test range system for large-scale target characteristic testing in a shorter distance

In the acoustic scattering and characteristic tests of large targets and large-scale transducers, in order to meet the plane wave conditions, the larger test distance is often required. It is a greater difficulty for the testing laboratories with limited space. In order to compact the testing distance and solve the problem of requiring a long distance for large-scale target scattering and large-scale transducer testing, based on the principle and application of microwave compact test rang system and the approximation of electromagnetic wave and acoustic wave, an underwater acoustic compact range test system (ACTRS) is proposed. The developed ACTRS uses a parabolic main reflector to obtain a plane wave at a short distance. Compared to the traditional underwater acoustic test system, the space distance is effectively compacted and the conversion process is reduced. Moreover, as the main device in the proposed ACTRS, the air-cavity with resin honeycomb structure was selected as the basic unit cell of the main reflector for the good underwater acoustic reflection performance. In addition, the edge sawtooth structure was selected to reduce the interference of edge diffraction in the quiet zone. Subsequently, the main reflector was simulated, trial-produced and measured. The measurement result shows good agreement with the simulation result. Finally, based on the proposed main reflector, the ACRTS was constructed for the object scattering and transducer directivity measurements. The test results were consistent with the simulation and the manufacturer’s manual data. Overall, the designed ACTRS can be used for large-scale target scattering and transducer directivity testing, providing a new reference for exploration of acoustic measurement methods.

Research on Acoustic Reflection Characteristics of Typical Concave Body based on COMSOL

In the design of an underwater acoustic imaging system, to improve the signal-to-noise ratio (Snr) of the signal receiver and achieve good acoustic imaging results, it is necessary to discuss the acoustic focusing problem of the concave body. Based on COMSOL finite element analysis, this paper makes a comparative analysis of concave structures in several typical acoustic reflection modules, takes plane waves as the background sound field, analyses the acoustic reflection performance of typical concave structures at different wavelengths and angles of incidence, and studies the acoustic convergence effect under different concave structures, providing reference and help for further optimizing the design of acoustic imaging systems.

Imaging ocean water columns by acoustic contrast reflection signals in existing marine seismic data

Marine seismic surveys conducted for oil and gas exploration use a source-receiver system consisting of airgun sources and hydrophone receiver arrays. The collected data were commonly used to image subsurface beneath the seafloor. The surveys had also collected signals of acoustic reflections from ocean water columns due to acoustic impedance contrast by temperature and salinity. These signals can be processed to provide high-resolution images of the water-column structures such as eddies and internal waves, forming a discipline termed as seismic oceanography in the literature. Acoustic contrast reflection signals in a three-dimensional seismic survey, collected by multiple parallel receiver arrays, can even be used to explore movements of water columns {see our recent study in [Zou,etal., Ocean Sci. 17(4), 1053–1066 (2021)]}. Nevertheless, because of the low acoustic impedance contrast in oceans, these water-column reflection signals are extremely weak, e.g., about 2–3 orders weaker than the seafloor reflections. Meanwhile, these signals consist of acoustic multipath features that require an appropriate filtering of the signals (see our recent study in the study by Zou and Zhang [JASA 150(5), 3852–3860 (2021)]. Understanding of the signal features and appropriate applications of acoustic signal processing methods are inspired to improve the imaging quality.

Modeling acoustic propagation on Mars

It is important to understand how the atmospheric conditions affect the propagation of sound waves on Mars, both for the study of the acoustic sources and of the atmosphere itself. As 3 microphones are already on Mars (2 on NASA/Perseverance and 1 on CNSA/Zhurong) and potentially more to come, a model of the propagation of sound in the Martian surface layer was needed. A first-principle acoustic attenuation model is used to quantify the excess attenuation of the Martian atmosphere. Thanks to inputs extracted from a global circulation model of Mars (the LMD Martian Climate Database), we are able to compare the magnitude of attenuation at different places and times, from 10 Hz to 20 kHz. Propagation effects are also considered by adapting a parabolic equation code to the Martian conditions. This accounts for strong temperature gradients near the surface, as well as gradients of wind speed. The acoustic reflection on the ground assumes a semi-porous medium. The turbulent fluctuations of temperature and wind speed are implemented using the frozen medium approach. The model shows that characteristics of sound waves propagation depend drastically on the local time. It provides a useful framework to interpret acoustic signal recorded on Mars. The model shows that characteristics of sound waves propagation depend drastically on the local time. It provides a useful framework to interpret acoustic signal recorded on Mars.

Improving passive acoustic target detection using machine learning classifiers

The ocean covers 70% of the Earth surface area, yet over 80% of it remains unexplored despite the advances in underwater acoustics and oceanography. Ocean exploration is critical for accurate climate model development, renewable energy applications, and in understanding the marine habitat. Further exploration necessitates improvements in underwater navigation with Autonomous Underwater Vehicles (AUVs). Utilizing acoustic landmarks can enhance AUV localization performance [Fula et al., Oceans IEEE/MTS (2018)]. Passive markers called Acoustic Identification (AID) Tags have unique and identifiable acoustic reflection signatures designed to function as landmarks [Satish et al., JASA 149 (2021)]. These targets can be detected by Match Filtering returns with template signals. Match Filtering performance is limited in the presence of strong interfering signals, and with changes in sound speeds that alters the temporal structure of these signatures. The application of a Machine Learning classifiers for detecting AID tag signatures can improve the localization performance. Through implementation of Logistic Regression, Deep Neural Networks, and Convolutional Neural Networks, the generalizability and superiority of these models is demonstrated. We report high accuracies (>90 %) in a multilabel (8 classes) classification task with signals with low SNR (–6 dB) and strong interference (+12 dB).

Binaural externalization processing method for object-based audio rendering

In both entertainment and professional applications, conventionally produced stereo or multi-channel audio content is frequently delivered over headphones or earbuds. Use cases involving object-based binaural audio rendering include recently developed immersive multi-channel audio distribution formats, along with the accelerating deployment of virtual or augmented reality applications and head-mounted displays. The appreciation of these listening experiences by end users may be compromised by an unnatural perception of the localization of frontal audio objects: commonly heard near or inside the listener’s head even when their specified position is distant. This artifact may persist despite the provision of perceptual cues that have been known to partially mitigate it, including artificial acoustic reflections or reverberation, head-tracking, individualized HRTF processing, or reinforcing visual information. In this paper, we review previously reported methods for binaural audio externalization processing, and generalize a recently proposed approach to address object-based audio rendering.

3D trajectory inversion of an adjacent well using scattered P-wave

In oil and gas exploitation, cluster well technology can significantly reduce costs and improve efficiency. An effective adjacent well detection method can greatly reduce the risk of collision between adjacent wells. This study proposes a method to invert the 3D trajectory of an adjacent well using a scattered P-wave obtained by borehole azimuthal acoustic reflection imaging. After obtaining the scattered P-wave from the raw data of the target well using the wave field separation technology, the waveform data in an imaging profile can be obtained by the downhole acoustic directional reception technology. Migration imaging technology is then used to obtain the image of the formation in the imaging profile. Subsequently, by analyzing the images of the formation in the imaging profile of the different azimuths, the well spacing and azimuth of the target well can be determined. Finally, the 3D trajectory of the target well can be obtained by solving the inversion equation. This method was validated by processing the field data from a deviated well in a deep formation. The comparison of the inversion and actual trajectories of the target well demonstrated that the maximum deviation of the inversion trajectory is 0.9 m in the north-south direction, 0.78 m in the east-west direction, 1.45 m in the well spacing, and 2.48° in the azimuth. The field data inversion result demonstrated that the method can effectively use the azimuth reflection acoustic data to invert the 3D trajectory of an adjacent well, which indicates that the borehole azimuthal acoustic reflection imaging technology has great potential within the context of adjacent well detection.

Controls on shallow gas distribution, migration, and associated geohazards in the Yangtze subaqueous delta and the Hangzhou Bay

Shallow gas is generally extensively distributed in the Holocene muddy sediments and gas seepage has been increasingly reported to induce geohazards in coastal seas, but controls on gas distribution and migration remain elusive. This study explores gas distribution and migration in the Yangtze subaqueous delta and the Hangzhou Bay using high-resolution acoustic profiles and core data. Shallow gas is widely detected by the common presence of acoustic anomalous reflections including enhanced reflection, gas chimney, bright spot, acoustic blanking, and acoustic turbidity. The gas front depth is generally less than 17.5 m, and is meanly shallower in the Hangzhou Bay than in the Yangtze subaqueous delta because of relatively shallower water depth and coarser Holocene sediments in the Hangzhou Bay. Shallow gas is inferred to be a biogenic product, and its distribution is highly contingent on the Holocene stratal thickness and water depth. Active gas migration and seepages are evident, and recently increasing occurrences of gas seepage can be ascribed to global warming and seabed erosion due to sediment deficit. The findings warn us to pay more attention to the positive feedback loops of gas seepages with global warming and seabed erosion for the associated geohazard prediction and reduction, typically in the highly developed coastal regions.

Analysis of unsteady flow field and near-field aerodynamic noise of scale high-speed trains in long tunnel

The hybrid LES/APE method is used to simulate the unsteady flow field and the near-field aerodynamic noise of a 1/25 scale eight-coach high-speed train in long tunnel, validated by time-averaged pressure coefficients and Power Spectral Density of surface pressure from the aerodynamic wind tunnel test of a same scale two-coach train model. Train induced wind with the maximum velocity of 28 m/s in the opposite direction of train operating is formed in tunnel. Blocking effect leads to larger turbulent pressure and streamwise increment of turbulent power level from 133.7 dB to 138.2 dB, which is from130.3 dB to 133.4 dB in open air. With APE solver, three cases including tunnel with fully reflective walls, tunnel with fully absorptive walls and open air, are conducted to compare the influence of blocking effect and acoustic reflection on sound pressure. Total sound pressure level on the train body in tunnel is overall stronger than that in open air. The difference of sound power level between tunnel and open air is mostly contributed by acoustic reflection: 84.7 % at Coach 1, 84.3 % at Coach 8 and 66.0 ∼ 77.5 % from Coach 2 to Coach 7. Five peak frequencies: 520 Hz, 800 Hz, 1440 Hz, 2600 Hz and 3880 Hz are found from the frequency spectra of sound pressure of the probes in bogie cavities and pantograph grooves, in tunnel with fully reflective walls. Sound pressure modes help to clarify the generation mechanisms of peak frequencies: 520 Hz and 800 Hz are caused by the tunnel cavity resonance; 1440 Hz is caused by the first-order vertical mode from the bottom of the pantograph groove to the top of tunnel walls; 2600 Hz is caused by the first-order vertical mode from the ground to the top of bogie cavity, but 3880 Hz is not generated by simple in-phase cavity resonance.

Impact of self-excited cavitating waterjet feeder pipe on acoustic and erosion patterns

The impact of the feeder pipe geometry on the dominant frequencies and erosion patterns induced by self-excited cavitating waterjets, SECJ, is studied using laboratory experiments. Complementary inspection of the bulk flow in the feeder sections is illustrated using averaged governing equations. The experimental results indicate that the feeder pipe length, L2, affects the acoustic characteristics of the waterjets. As an acoustic reflector, the length of feeder pipes induces distinct transmission losses, resulting in resonant intensity changes and reflectivity. The relatively larger section of the feeder section with respect to the upstream fitting led to the formation of a large-scale recirculation pattern due to a sharp shear layer from the incoming flow. This recirculation bubble may cover the entire or a fraction of the feeder extent depending on L2. Overall, the work offers insight into the design of required pipe system parameters to modulate peak resonance.

The use of a parametric array source and nearfield scanning in the characterisation of panel materials for underwater acoustics

The properties of the materials used in underwater acoustics are important for applications such as acoustic windows, reflectors and baffles, acoustic barriers or screens, decoupling materials, and anechoic coatings. To characterise the performance of such materials at frequencies above 1 kHz, measurements are typically undertaken on samples of the material in the form of finite sized panels. Such measurements suffer from uncertainty due to the finite size of the panel (leading to contaminating signals from edge diffraction), and the difficulty in simulating the ideal plane-wave insonification. This paper describes work at the UK National Physical Laboratory to minimise these effects by use of: (i) a parametric array as a sound source that provides a directional beam and short broadband pulses; and (ii) nearfield scanning using a hydrophone to sample the complex sound pressure field interacting with the test sample, decomposing the sound field into its plane-wave components. Results are presented of these techniques applied to measurements in laboratory test tanks at frequencies between a few kilohertz and a few hundred kilohertz to determine the reflection and transmission performance of a range of test samples, including panels consisting of homogeneous polymers and materials with regular periodic structure.

The dependence of transformer sound power measurement accuracy on microphone configurations in the anechoic chamber.

The paper is aimed at investigating the number and location of microphones required to accurately calculate the sound power level of a harmonic noise source. The measurement procedure performed is based on the IEC standard for the determination of transformer sound power level. The current procedure defines numerous measurement points around the tested transformer. Reducing the number of measurement points could significantly speed up the measurement procedure when a transformer is tested during the manufacturing process. Within the research work, estimations on the number and location of measurement points are identified to accurately calculate sound power level. The approach is tested and validated using specially developed software in LabView, that allows inclusion or exclusion of measurement points from the sound power level calculations. To prevent harmonic wave interference, acoustic wave reflections and background noise, the measurement procedure took place in the anechoic chamber.