bluuebunny/crossref_metadata_2025 huggingface dataset:
Reciprocity, passivity, and causality in fully coupled acousto-electrodynamic media
Authors: Gokani Chirag A. , Wallen Samuel P. , Haberman Michael R.
Published: November 2023

Multiple-scattering homogenization procedures in acoustics and electromagnetics have shown that subwavelength asymmetries and lattice effects in metamaterials give rise to bianisotropy, the tensorial coupling of two constitutive relations. Asymmetric piezoelectric scatters in the quasi-electrostatic regime have recently been shown to couple the electric field to the bianisotropic elastodynamic relations, yielding an additional, emergent property termed electro-momentum coupling. To facilitate the study of scatterers responsible for electro-momentum coupling, Wallen et al. [Proc. Mtgs. Acoust. 46, 065002 (2022)] and Lee et al. [J. Appl. Phys. 132, 125108 (2022)] abandoned the quasi-electrostatic approximation in favor of a simultaneously acoustic and electrodynamic scatterer. We previously used a multiple-scattering homogenization procedure to show that a collection of such scatterers gives rise to constitutive relations that fully couple acoustics and electrodynamics. Now, we derive bounds on these fully coupled relations due to reciprocity, passivity, and causality. These results recover known bianisotropic and piezoelectric bounds and reveal that the imaginary parts of the additional electro-momentum and magneto-momentum coupling coefficients vanish in lossless, reciprocal, and passive media. The bounds also verify that the constitutive relations derived by our homogenization procedure satisfy reciprocity, passivity, and causality. [Work supported by DARPA and ARL:UT McKinney Fellowship in Acoustics.]
Cortical processing of Mandarin lexical tone in children with different language backgrounds
Authors: Cajas Samantha , Baron Rigel , Diaz Andres , Guo Sharry , Bianchi Maria , Yu Yan H.
Published: November 2023

Bilingual experience modulates cognitive skills, particularly executive control. However, it is not clear if such modulation can be observed in automatic speech processing. Furthermore, it is unknown if bi-dialectal experience will enhance speech processing. This study aims to investigate whether and how early bilingual experience influences cortical sensitivity for automatic cortical processing of speech, specifically in the context of tonal and non-tonal languages. A passive listening oddball paradigm with two lexical tone contrasts were used and event-related potentials were recorded. An easy contrast (tone 1 versus tone 3) and a hard contrast (tone 2 versus tone 3) were used as the stimuli. Children between 5 and 10 years of age were tested. Preliminary results indicate that monolingual mainstream English, African-American English, and bilingual Mandarin-English learners all showed similar brain responses to the easy lexical tone contrast. However, there was an age effect across language groups. Such results suggest that biological factors such as age are stronger predictors of brain responses to lexical tone contrasts comparing to the factor of language background.
An active noise control algorithm based on an improved convex combination loop
Authors: Yang Xu , Lin Tian Ran
Published: November 2023

The conflict between a faster convergence using a Filtered-X Least Mean Square (FXLMS) algorithm and the requirement of a small steady-state error of an adaptive active control (ANC) system which limits its performance in terms of computation efficiency and the control error. The problem can be solved by using two paralleling adaptive filters to form a convex combination loop in the control system. However, the exponential weight function used in the original convex combination loop design can consume a large computer power which has limited its application. As a result, a new weight function is proposed to replace the original exponential function in the original convex combination loop to enhance the convergence rate of the adaptive ANC system. Furthermore, a MRFXLMS algorithm is used to replace the FXLMS algorithm in the ANC system so that it can be used for impulse noise control. The result shows that the proposed algorithm performs well in the control of input impulse noise with different intensity.
Sea ice mechanical property inference using cryophones and coherent signals
Authors: Reeder D. Benjamin , Joseph John , Wheeler S. Kyle
Published: November 2023

Mechanical properties of Arctic sea ice can be inferred by observation of the speeds of compressional, shear and flexural waves generated through in-ice conversion of impulsive energy. In prior work, the impulsive signal was generated by a lead ball or sledge hammer dropped onto the top of the sea ice, and the inversion process required meticulous, manual extraction of signal amplitudes. The work presented here makes use of (a) coherent sources with which broadband signals can be generated to replace the manually generated hammer-drop signals and improve accuracy via matched filter, as well as (b) recent observations and modeling of ice sheet compressional resonances from which ice thickness can be more easily inferred. Analysis and modeling of observations from a recent field experiment in the Beaufort Sea are shown that demonstrate the potential capability of remote monitoring of sea ice mechanical properties.
Sound absorption by a soft medium embedded with complex-shaped hard inclusions
Authors: Sharma Gyani Shankar , Skvortsov Alex , MacGillivray Ian , Kessissoglou Nicole
Published: November 2023

Acoustic coatings for marine applications are commonly designed using a soft elastic matrix embedded with an array of resonant inclusions. In this work, a simple analytical approach to predict the acoustic performance of a soft elastic matrix embedded with hard inclusions of complex shape is presented. Utilizing analogies from fluid dynamics and electrostatics, a small number of well-known lumped parameters such as the added mass and capacitance are employed to relate the dominant dipole component of scattering of a complex-shaped hard inclusion to that of an equivalent sphere. Effective acoustic properties are then derived using a homogenization. The absorption coefficient of the coating for a range of complex shapes is compared with numerical simulations.
Predicting the acoustic response of a cylindrical shell immersed in an underwater waveguide using a substructuring technique
Authors: Kha Jamie , Dumortier Florent , Karimi Mahmoud , Maxit Laurent , Meyer Valentin
Published: November 2023

Sound radiation from structures in an underwater waveguide presents a challenging underwater acoustics problem typically resolved with numerical methods. This can be computationally inefficient and limited to low-frequency analysis. Hybrid approaches improve on these limitations by combining numerical methods with analytical solutions. This study utilises a substructuring technique called the condensed transfer function approach (CTF) and a decoupling technique called the reverse condensed transfer function approach (rCTF). The hybrid CTF-rCTF approach builds systems by coupling and decoupling simpler subsystems. Each subsystem is represented at the junction interfaces, described by condensed transfer functions (CTFs) that can be analytically or numerically determined. These CTFs are decomposed into orthonormal condensation functions (CFs), for example, gate or exponential functions. To demonstrate the potential of CTF-rCTF, the acoustic response of an infinitely long cylindrical shell under line-distributed load and immersed in an underwater waveguide composed of an upper free surface and lower rigid floor is predicted. This system is built from an underwater waveguide decoupled with a fluid volume and coupled with an excited shell that takes place of the decoupled fluid. Acoustic pressures received in the fluid domain are predicted and verified against an analytical solution. It is particularly shown that using exponential functions as the CFs improves the prediction quality compared to gate functions.
Dynamics and acoustics of bubbly plumes
Authors: Skvortsov Alex , Zhu Shuang J. , Manasseh Richard , Ooi Andrew , Kocan Martin
Published: November 2023

Transient bubbly plume dynamics including their effects on the free surface were studied numerically using a simple numerical model based on integral theory [1, 2] and Eulerian–Eulerian coupled large Eddy simulation (EE-LES) method. The EE-LES model was validated with the interfacial closures evaluated for drag, lift and virtual mass forces. The simulation data showed good agreement with both numerical predictions and experimental measurements in the literature. The spectrum of the surface pressure fluctuations and acoustical pressure induced by a bubbly plume were extracted from numerical simulations [3]. The effect of interaction of two plumes is discussed. [1] B.R. Morton, G.I. Taylor, J.S. Turner, Turbulent gravitational convection from maintained and instantaneous sources, Proc. R. Soc. Lond. A234, 1–23 (1956) [2] A. Skvortsov, T. DuBois, M. Jamriska, M. Kocan, Scaling laws for extremely strong thermals, Phys. Rev. Fluids 6, 053501 (2021) [3] S.J. Zhu, A. Ooi, R. Manasseh, A. Skvortsov, Prediction of gas holdup in partially aerated bubble columns using an EE-LES coupled model, J. Chem. Eng. Science 217, 115492 (2020)
Geoacoustic inversion of wide-angle reflection-coefficient data to estimate sediment shear properties
Authors: Dosso Stan , Holland Charles W. , Dettmer Jan , Jiang Yong-Min
Published: November 2023

This paper considers Bayesian geoacoustic inversion of broadband, wide-angle reflection-coefficient data including shear parameters in the seabed model to investigate the ability to estimate these parameters as well as effects on the estimation of other geoacoustic parameters, particularly compressional-wave attenuation. The seabed parameterization is based on the viscous grain-shearing (VGS) sediment-acoustic model, including the grain-to-grain shear modulus as an unknown parameter. VGS sediment parameters are transformed to density and frequency-dependent compressional- and shear-wave speeds and attenuations. Data prediction involves spherical-wave reflection-coefficient calculations. Trans-dimensional inversion, which samples probabilistically over the number of layers in the seabed model, is applied to combine quantitative model selection with parameter/uncertainty estimation. The inversion is applied to reflection-coefficient data sets collected on the New England Mud Patch, and inversion results are compared to those obtained under the common assumption of negligible shear effects (i.e., inverting for a fluid sediment model).
Improvement of sound insulation on the modular housing
Authors: Lee Wonhak , Kim Soyoung , Han Sungjae
Published: November 2023

The modular construction method is an architectural technique in which buildings are produced in factories and then assembled on construction sites to complete the construction process. This method has two main advantages. First, since the construction takes place in factories, it can reduce construction waste. Second, it can shorten the construction period on the site. So there is considerable interest in using the modular construction method for the construction of residential buildings. In this study, the purpose of the modular construction method in the case of residential buildings is to improve the indoor sound insulation. For this purpose, first, the sound insulation performance of the walls and floor structures has been predicted through simulations at the design stage. Second, the sound insulation performance of the walls and floor structures has been measured using mock-ups in the factory and compared with the simulation results. Third, the sound insulation performance of the walls and floor structures in the actual completed building has been measured and compared with the performance of the simulations and mock-ups. As a result, we have compared the performance of modular construction from the design stage to the completion of the building. Through this process, we have presented procedures for improving the sound insulation performance of the building and quality management, from the design phase to the post-construction stage.
Enhancing acoustic comfort with window coverings: Reducing sound transmission and reverberation times with a single product
Authors: Cazzolato Benjamin , West Cameron , Schembri Tyler , Watkins Peter , Robertson Will
Published: November 2023

Window coverings have traditionally been used for design and light control only. However, they also present a great opportunity for a complete acoustic treatment. This is for a number of reasons: (1) They are installed over glazing which represents the typical weak point through which sound enters the space; (2) they have a large surface area for absorption; and (3) they are a natural fit in most modern spaces allowing architects, designers, and clients freedom in their design unconstrained by acoustics. By combining mass loaded vinyl to target sound transmission and absorptive surface linings to provide sound absorption, it is possible to significantly improve acoustic comfort with installation of acoustic curtains. This paper presents the results of extensive laboratory tests on such acoustic curtains, where the diffuse field sound reduction index and sound absorption coefficients were measured for four glazing conditions (open window, 4 mm glass, 6.38 mm glass, and 10.38 mm glass) with 15 different curtain configurations, totalling 76 tests. The results demonstrate significant sound level reductions with the addition of the curtains, with a weighted noise reduction index improvement as high as 13 dB, and a noise reduction coefficient of 0.65 for an additional 2 kg per square metre.
Floor impact sound reduction and impact absorption performance of floor mat
Authors: Song Gukgon , Song Hansol , Yoon Yongjin
Published: November 2023

In Korea, the post evaluation system of floor impact sound performance was implemented in August 2022. Therefore, it is necessary to check the floor impact sound performance after the completion of the apartment. If a floor impact sound performance does not meet the regulation limit, compensationm and follow-up renovations are required. In this study, in order to develop a floor mat that can reduce heavy weight floor impact sound, the floor impact sound reduction performance and impact absorption performance of each condition of the sample were confirmed. Floor impact sound reduction performance was measured using the test methods of KS F 2865 and ISO 10140-3, and impact absorption performance was measured according to the test method of JIS A 6519. As a result of the measurement, the performance of reducing floor impact sound showed a clear difference in performance according to thickness rather than material type. Impact absorption performance was found to be affected by surface hardness and material thickness. In conclusion, it is considered that the selection, thickness, and surface hardness of materials are important design factors when developing floor mats.
Estimation of seafloor properties in shallow oceans using minimally processed vertical directivity of surface-generated ambient noise
Authors: Jones Adrian D.
Published: November 2023

Typically, data from an array with vertical aperture will be beam-formed to provide the level and variation of spectrally averaged ocean ambient noise as a function of vertical angle. This paper considers the potential for such measurements to provide information about the acoustical properties and layering of a seafloor in a shallow ocean. First, with the assumption of dipole surface sources, it is feasible to describe the ambient noise in the near-horizontal in terms of the Weston α parameter (Weston, J. Sound Vib. 18, 271–287, 1971). Furthermore, measurements of ambient noise in the positive and negative vertical directions may be used to provide a spectrally averaged determination of bottom loss. With the presence of a surficial seafloor layer, each of the near-horizontal and near-vertical noise intensities will exhibit spectral variation. Techniques are described by which such relative variations in noise directivity, over a frequency span of some octaves, enable a reasonable estimation of, first, the thickness of a seafloor layer, and second, the acoustical properties of the layer and the seafloor basement.
Evidence of oceanic and atmospheric tides in underwater ambient noise time records
Authors: Eller Anthony I. , Heaney Kevin D. , Bradley David L.
Published: November 2023

Multiyear time records of low-frequency ocean ambient noise show clear evidence of a modulating influence by major semi-diurnal and diurnal gravitational tides. These are displayed by means of a variance spectral analysis of noise time records obtained from the United Nations Comprehensive Nuclear Test Ban Treaty Organization for hydrophone stations at Wake Island, Ascension Island and Diego Garcia. Narrow-band noise frequencies ranged from ½ to 10 Hz. There is also evidence in the noise records of a diurnal atmospheric tide related to solar radiation and atmospheric loading. This same tidal presence is seen in wind speed records as well. Part of the challenge in the analysis is to distinguish between expected diurnal behavior in wind speed, with its accompanying effect on ambient noise, and the presence of actual tidal lines. A brief history of earlier observations of diurnal variation in underwater acoustics is presented, along with some suggestions of causal mechanisms.
Vector acoustic observations of underwater noise energetics over a 24 h period in Puget Sound, Washington, as influenced by ferry and ship traffic
Authors: Dahl Peter H. , Dall'Osto David R.
Published: November 2023

Vector acoustic measurements of underwater noise made continually over a 24-h period within a small bay on the west side of Puget Sound, Washington State are discussed. The bay contains the Washington State ferry landing at Kingston with measurement site approximately 1 km distant from the landing, at water depth 42 m. Periodic, nearby ferry traffic, and episodic large-vessel shipping activity punctuate the observations which will be compared with those made in deeper waters. Potential and kinetic energies in key shipping decidecimal bands are equal within calibration uncertainty; a practical result towards the inference of kinematic properties from pressure-only measurements within inland waters complementing similar results obtained in off shore waters. An important exception exists when the noise field is dominated by a vessel passing directly over the sensor, as was demonstrated by the deployment vessel moving at speed 7.5 knots. Observed near the seafloor, broadband noise emissions from a vessel passing directly above exhibit frequency bands where potential acoustic energy is greater than kinetic energy (and vice versa in neighboring frequency bands). This phenomenon is also examined with a model based on multiple interfering reflections from the seabed, sea surface, and buried sediment layers.
Large-aperture wide-bandwidth densely populated coherent hydrophone array system for ocean acoustic monitoring
Authors: Radermacher Max K. , Schinault Matthew E. , Britton Anthony , Seri Sai Geetha , Mohebbi-Kalkhoran Hamed , Makris Nicholas C. , Ratilal Purnima
Published: November 2023

Underwater acoustic monitoring with a large-aperture coherent hydrophone array is advantageous because it enhances signal-to-noise ratio of received signals, provides estimates of signal bearing, and enhances signal detection ranges by one to two orders of magnitude over that of a single hydrophone. A large aperture coherent hydrophone array system comprising >160 elements has been developed inhouse at Northeastern University. The overall acoustic aperture length is 192 m with array elements nested into multiple uniformly spaced or log spaced subapertures. Hydrophones with integrated broadband pre-amplifiers designed with a linear frequency response from 10 Hz to 50 kHz send differential pair amplified and filtered analog signals to multiple 24-bit, 32-channel analog-to-digital converters with sampling rate that is programmable up to 100 kHz per channel. Array internals are designed using field replaceable pressure tolerant components verified by pressure chamber testing. Forward and aft modules are equipped with non-acoustic sensor elements to provide depth, heading, pitch, roll and temperature measurements. Acoustic aperture telemetry is user datagram protocol (UDP) converted to single-mode fiber for transmission along 600 m of faired tow cable to a shipboard data acquisition system. Examples of passive acoustic data from array deployment in the US Northeast coast are presented illustrating array capabilities.
Noise levels in a changing Arctic Ocean and its implications for security
Authors: Giorli Giacomo , Russo Aniello , Carniel Sandro
Published: November 2023

Arctic Ocean is undergoing an “Atlantification” of its oceanographic properties. Sea ice retreat and reduction of sea ice age will affect its underwater soundscape, with anthropogenic noise expected to increase due to the exploitation of new maritime routes. The CMRE’s Environmental and Operational Effectiveness Programme conducted a study of the new Arctic oceanographic conditions and ambient noise by deploying in 2021 and in 2022 different moorings equipped with passive acoustic recorders and oceanographic sensors. Data did not show a clear relation between sea-ice concentration and noise levels in the marginal ice zone. However, noise levels indicate that the possible presence of transmissions ducts might increase high frequency noise in the subsurface area. Seasonality and variations in the overall soundscapes were also evident by the presence of sounds from biological sources. In 2023, with the support of the NATO Office of the Chief Scientist, CMRE started a long-term scientific endeavor to study how climate change might affect the Alliance’s security in the maritime domain. A significant research effort is focused on the Arctic, and in June–July 2023 CMRE deployed three deep moorings for monitoring the acoustic-oceanographic conditions in the long term. [Work supported by the NATO Allied Command Transformation.]
Marine and lacustrine ice fracture detection
Authors: Case John A. , Barnard Andrew
Published: November 2023

Ice fracturing has been extensively studied and modeled. With increased interest in ice mechanics and fracturing in recent years in climate science, fisheries, and for cultural impacts, detecting and classifying fracturing events has become an important problem to consider. Fractures primarily occur due to stress relief within an ice sheet during temperature shifts and ice movement. These events create mechanical waves within the sheet that couple into the water column which can then be detected as pressure and particle velocity fluctuations. Machine learning algorithms will be used to detect and classify ice cracking events though their acoustic signature. Different models will be compared to one another for effectiveness and accuracy. Data will be shown from several different locations, including Northern Alaska and the Great Lakes.
Ocean ambient noise field modelling and the optimized noise term
Authors: Kovaloff Nikita
Published: November 2023

The objective of this thesis is to determine the frequency and wind-wave forcing dependent effective sea surface noise source level per unit area extracted from the hourly minimum sound power levels of six month-long acoustic recordings. The effect of the propagation environment is accounted for using Bellhop. The simulated environment is configured using climatological sound velocity profiles to capture seasonal effects and bottom sound speed estimates made from seabed sediment maps. Hourly meteorological data were extracted from ERA5 providing relevant wind and wave parameters from which noise levels may be predicted. A weighted composite model consisting of neutral wind and significant wave height leveraging the two-term exponential regression function proved to maximize model R2. Received level data originating from 16 hydrophone stations in the North Atlantic and Labrador Sea were combined with the Bellhop TL simulations in order to produce estimates of the effective noise source level per unit area (NSL/A) for changing surface environmental conditions and inter-compared. Hourly minimum sound power level derived model-data comparisons using horizontal wind speed magnitude 10 m above sea level expressed a decrease in NSL/A estimates versus Kewley (1990) by 10 to 15 dB from 1 to 3 kHz.
A general model for sediment-column structure on the New England Mud Patch from Bayesian geoacoustic inversion of seabed reflection data
Authors: Jiang Yong-Min , Holland Charles W. , Dosso Stan , Dettmer Jan
Published: November 2023

Muddy sediments cover significant portions of continental shelves, but their physical properties remain poorly understood compared to sandy sediments. To explore the spatial and frequency dependencies of mud properties, wide-angle seabed reflection coefficients versus grazing angle and frequency were measured on the New England Mud Patch (NEMP) during the 2017 Seabed Characterization Experiment. This paper presents trans-dimensional Bayesian inversion of reflection coefficients within a frequency band of 1–3 kHz and an angular range of ∼15–25° to obtain geoacoustic profiles and associated uncertainties, as well as frequency dependencies of sound speed and attenuation. The estimated geoacoustic profiles are similar to those from previous inversions of reflection-coefficient data at lower frequencies (0.4–1.3 kHz) collected at two different sites on the NEMP. Based on the inversion results at all three sites, a general interpretive model for sediment-column structure and variability is synthesized for the NEMP. This model includes an upper mud layer in which sediment properties change slightly with depth due to near-surface processes, an intermediate mud layer with uniform properties, and a transition layer where properties change rapidly with depth due to increasing sand content in the mud above a sand layer. [Work supported by the Office of Naval Research.]
Sparse underwater acoustics signal reconstruction on shallow water and its performance evaluation
Authors: Arifianto Dhany , Prasetyo Aprianto D.
Published: November 2023

We performed a simple underwater acoustics signal transmission on an experimental pond and shallow water in Surabaya harbor. First, we tested the sparse reconstruction algorithm on the underwater signal transmitted in the experimental pond to evaluate the sparsity limit of reconstructed signal. The transmitted signal consisted of a train of sinusoidal and pure tone with variation of frequency and duration. From the results, it is concluded that the proposed algorithm performed well in our experimental pond. However, it performed poorly with respect to distance on a shallow water environment.
Enhancing remote sensing of water temperature using acoustic tomography and 3-D-RPS algorithm
Authors: Gao Yixin , Xie Xinyi , Wei Danni , Huang Haocai
Published: November 2023

Remote sensing of water temperature and flow dynamics is of paramount importance for water environment management. Coastal acoustic tomography (CAT), an innovative method for remote sensing in underwater environments, utilizes the dual-way travel time of multiple sound paths to reconstruct the underwater temperature field. However, the transmission experiments are susceptible to data noise caused by station drift and inaccuracies in travel time extraction. In this study, a three-dimensional Rousseeuw Phase-Space (3-D-RPS) thresholding algorithm is proposed to remove outliers in the travel time data obtained from Huangcai Reservoir using three CAT systems on September 16, 2020. Additionally, this work includes grid partitioning based on sound path propagation, calculation of sound path lengths, and reference transmission time within each grid, construction of a sparse matrix, and inversion of the two-dimensional temperature field and its associated inversion error. The accuracy and applicability of the proposed method are confirmed through a comparison with data obtained from temperature–depth (TD) sensors. The results demonstrate the precision and suitability of this approach. By effectively mitigating the impact of station drift and extraction accuracy issues, this method provides a reliable temperature field estimation.
Ultrafast plane wave imaging of breast lesions
Authors: de Korte Chris L. , Hendriks Gijs , Radicke Marcus , Mann Ritse
Published: November 2023

Ultrafast plane wave imaging has great potential for 3-D functional ultrasound imaging but also comes with decreased lateral resolution, contrast, and penetration depth with respect to conventional imaging (CI). By utilizing coherent plane-wave compound imaging (CPWCI) and different beam forming techniques (Delay and Sum (DAS), Stolt’s-fk, and Lu’s-fk), we have demonstrated to improve resolution, penetration, and contrast-to-noise ratio. In this work we evaluate this technique in patients. A Siemens Sequoia system equipped with an 18L6HD, 14L5, and 10L4 was used to acquire CI and CPWCI data in 77 patients suspected of breast cancer visiting our clinic. CI data was acquired at three angles (-11, 0, and 11 degrees) and beamformed in the Sequoia and incoherently compounded while CPWCI data was acquired for 33 angles (-16:1:16 degrees) and subsequently processed off-line. In total, 9 malignant lesions, 35 benign lesions, and 32 normal other structures were found. For all three transducers, improved penetration was observed with CPWCI compared to CI. Additionally, contrast to noise ratio was also improved by CPWCI, especially at larger imaging depths. Qualitatively, an improved resolution appeared to be present, probably also caused by the improved contrast. Currently, a reader study in which radiologists have to score CI and CPWCI images sight by side while blinded to the acquisition mode is being prepared to test the efficacy of CPWCI in clinical practice. In conclusion, CPWCI bears great promise for improved breast cancer detection.
A novel denoising strategy for ultrasound elastography
Authors: Kulam Magdoom , Basser Peter
Published: November 2023

Ultrasound imaging, while offering real-time tissue monitoring, portability, and other benefits, often suffers from poor signal to noise ratio (SNR). Noise has a particularly detrimental effect in US elastography since it gets amplified during the elastic modulus reconstruction process due to computation of high-order spatial derivatives of the deformation field needed to calculate the shear wave velocity within the sample. In this work, we introduce a novel scheme to denoise deformation fields using physically motivated “compatibility conditions,” which are imposed as constraints. These conditions, well established in the solid mechanics literature, ensure that the deformation field remains continuous without exhibiting cracks, folds, or slips. Spatially uncorrelated noise gets significantly reduced when we apply them. Importantly, this approach avoids unnecessary smoothing and the ensuing loss of accuracy commonly observed in other denoising methods. We demonstrate the efficacy of this method using planar deformation fields obtained from simulations and those measured on an elasticity quality assurance (QA) phantom using acoustic radiation force impulse imaging (ARFI). Our pipeline results in smoother elasticity maps with 2x improved SNR, confirming the effectiveness of the approach.
Real-time 3-D reconstruction from multiple simultaneous ultrasound scans for enhanced imaging
Authors: Antico Maria , Gillman Ashley , Belous Gregg , Lebrat Leo , Petersson Lars , Schmutz Beat , Mejan-Fripp Jurgen , Dowling Jason , Fontanarosa Davide
Published: November 2023

Ultrasound imaging offers numerous benefits compared to other modalities, including portability, affordability, and real-time volumetric imaging capabilities. However, its limited field of view hinders image interpretation, significantly limiting its potential clinical applications. This study focuses on creating tomographic ultrasound imaging by automatically registering partially overlapping 3-D ultrasound volumes (coarsely localized in space). This approach can be used to gather a comprehensive field of view of the anatomical area imaged and to enhance the acquired image information. Potential applications involve both tomographic/wide-view imaging using conventional ultrasound probes and future technologies, where multiple ultrasound probes will be able to scan simultaneously the anatomy of interest. This work describes the development of advanced artificial intelligence and image analysis methods to create real-time 3-D anatomical reconstructions of a designated area of interest. Simultaneously (or quasi simultaneously) acquired ultrasound volumes with partial overlap can be spatially aligned using rigid registration, because they present geometrically similar information. We used novel supervised and unsupervised transformers and compared the results with more traditional methods such as mutual information and cross-correlation. This application contributes to creating new imaging processing techniques for ultrasound imaging and making this complex modality more user-friendly and clinically usable.
Deep learning-based microbubble localization towards improved super-resolution ultrasound
Authors: Schoen Scott J. , Tehrani Ali K. , Samir Anthony E.
Published: November 2023

Ultrasound (US) is an indispensable tool for visualizing the microvasculature noninvasively. Over the last decade, US localization microscopy (ULM), which exploits microbubble contrast agents as effective point scatterers, has dramatically improved the spatial resolution attainable with US subject to the so-called diffraction limit (millimeter scale), and enabled mapping of vessels on the order of 10 μm. However, microbubble localization, a principal component of ULM, typically relies on bubble sparsity and compounding of many (102 to 104) frames. Thus, to enable sensitivity to more transient phenomena at the smallest scales, optimally sensitive and specific means of localization are required. Drawing on newly available ground truth data (ULTRA-SR Challenge, IUS 2022), we apply convolutional neural network (DeepLabv3) to perform localization via segmentation of the microbubble regions and identification of their centroids. Following training on 80% of the available simulated US frames, the network demonstrated localization precision 0.88 and recall 0.50 (tolerance of 0.5λ) on the test frames, with bias on the order of 0.1λ, and inference time of 40 ms on Nvidia RTX3090. Such accurate and sensitive localizations have significant promise toward elucidating hemodynamics at still finer spatial and temporal resolutions.
Wearable ultrasound system for assessing muscle function during physical activity
Authors: King Erica L. , Bashatah Ahmed , Guthrie Brian M. , Jones Margaret T. , Wei Qi , Sikdar Siddhartha , Chitnis Parag V.
Published: November 2023

Conventional ultrasound transducers, which are meant for hand-held operation, are not ideally suited for MSK-US during dynamic physical activity. We have developed a custom wearable ultrasound system for Motion-mode (M-mode) MSK-US, which enables multi-site hands-free sensing of tissue movement during physical activity such as that encountered during rehabilitation exercises. Participants performed a jumping task on a force plate with a sensor attached to their right vastus lateralis (VL). Mean pixel value (MPV) and normalized pixel differences (NPDs) were acquired from the images during the jumping task. Signals were filtered and normalized to root-mean square baseline and percent change was calculated for peaks of jump take-off and landing. The correlation coefficient was calculated to determine a relationship between metrics. Concurrently acquired force-plate data showed that the percent change during take-off and landing was 0.28% ± 0.09 and 0.66% ± 0.17 relative to baseline for each peak, respectively. MPV values changed 0.42% ± 0.29 and 0.81% ± 0.17, and NPD changed 0.41% ± 0.32 and 0.84% ± 0.12 for corresponding peaks. Overall results indicated significant correlation between force data and MSK-US (p < 0.05). Our system can maintain acoustic coupling during complex movements providing real-time feedback and expanding the potential for wearable MSK-US sensors.
Sensor fusion for simultaneous measurement of micro-vibrations
Authors: Phillips Luke , Oberst Sebastian , Sepehrirahnama Shahrokh
Published: November 2023

Low-amplitude micro-vibrations are common in nature and engineering, throughout structural applications, and biology. The ability to accurately measure and analyse these vibrations in the presence of noise (unwanted signal content) has far reaching consequences across many fields of acoustics. Methodologies for the enhancement and improvement of such signals are, therefore, sought. We explore the capability of sensor fusion in combination with Kalman filtering (KF), using pairs of accelerometers to improve measurement of low-amplitude micro-vibrations. Prior research of pairing sensor fusion with machine learning approaches like KF, support vector machines, or coherence analysis reported up to 90% reductions in “ghost” detections. This research attempts to extend this success to micro-vibrations where broadband noise, and external perturbations can have dramatic impacts on measurability. A pair of accelerometers has been placed both parallel and perpendicular to the axis of an excitation in pine timber planks of varying dimensions and cuts. Simultaneous measurement of ∼5 N excitations with an automated hammer at varying distances are recorded and patterns observed in the time domain through preliminary analysis in MATLAB. Features identifiable from this data become clearer as compared to conventional approaches and have potential applications in non-invasive early predictive analysis of structures for timber pest control.
Experimental investigations on aerodynamic and psychoacoustic characteristics of three-blade looprop propeller
Authors: Sun Jianwei , Yonezawa Koichi , Shima Eiji , Liu Hao
Published: November 2023

Aeroacoustic noise in multiple rotor drones has been increasingly recognized as a crucial issue. This study focuses on addressing this challenge by introducing a novel low-noise looprop propeller design with three blades. Unlike traditional propellers, the looprop propeller utilizes three closed-loops to generate thrust. Through comprehensive experimental investigations conducted in an anechoic chamber using a hover stand test, we conducted an integrated study of the propeller's aerodynamic, aeroacoustic, and psychoacoustic characteristics. The results demonstrate that the three-blade looprop propeller achieves a notable reduction in the overall sound pressure level (OASPL), particularly in tonal noise at the blade passing frequency where the tone reduction amounts to approximately 15 dB. Additionally, we employed Zwicker psychoacoustic annoyance models to evaluate the propellers' psychoacoustic performance and discussed the environmental noise mask effect. The findings indicate that the three-blade looprop propeller exhibits an improved sound quality while maintaining aerodynamic performance comparable to that of conventional propellers. Overall, our study suggests that the looprop propeller design offers significant advancements in acoustic performance, particularly in terms of psychoacoustic characteristics. These findings hold promising implications for the field of drone technology and the potential for notable improvements in noise reduction.
Analytical closed-form solution of the Navier–Stokes equations for the aerodynamic near-field and sonic boom from axisymmetric bodies
Authors: Miller Steven A.
Published: November 2023

An analytical closed-form solution is presented for the aerodynamic near-field and ground signature from an axisymmetric body with a low thickness ratio. The Navier–Stokes equations are formulated as a boundary value problem that incorporates the incoming ambient flow-field and the aerodynamic properties on the body surface. The shape of the aerodynamic body is defined as a product of generalized functions. A direct solution for the density of the aerodynamic near-field, represented as a function of both space and time, is proposed through the integration of the Navier–Stokes equations in a generalized functional form. Pressure, temperature, velocity, and Mach number are then derived in the near-field. The methodology, being fully nonlinear, surpasses the traditional F-function, impulse, and hypersonic similarity theories originally developed for near-field prediction. The presentation outlines the major steps in deriving the analytical solution and provides predictions from an aerodynamic body in the near-field, along with the associated ground signature. The methodology is focused on aerodynamic bodies operating at high-speeds, ranging from the supersonic to the hypersonic regime. [Work supported by the Defense Advanced Research Project Agency, under Grant No. W911NF-21-1-0342.]
Developments regarding Type II secondary sonic booms and topography
Authors: Sparrow Victor W. , Riegel Kimberly
Published: November 2023

Type II secondary sonic booms are those that reflect from the primary boom carpet, enter the stratosphere, and turn back toward the ground if the upper atmospheric winds are favorable. A study initially described by the authors at the Forum Acusticum meeting in September 2023 predicted that the Type II secondary sonic boom rays could be profoundly affected by small angle changes in the topography of the ground. The current work provides an update on those ray tracing predictions, namely, that the amplitudes of Type II secondary sonic booms are substantially reduced by the topography. Such results may explain why secondary sonic booms historically have been reported for supersonic operations over water but not for over land. A grid refinement study will also be summarized. [Work supported by the FAA through ASCENT Project 57 under the supervision of Sandy Liu. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the FAA.]
Measured turbulence statistics from two NASA sonic boom test campaigns
Authors: Anderson Mark C. , Gee Kent L. , Nyborg Kaylee , Loubeau Alexandra
Published: November 2023

Turbulence in the lower atmosphere can have substantial effects on measured sonic boom waveforms on the ground. These turbulent distortions vary spatially and temporally and are best understood statistically. Simultaneous atmospheric and acoustic data were acquired as part of the NASA Sonic Booms in Atmospheric Turbulence (SonicBAT) and Carpet Determination in Entirety Measurements (CarpetDIEM) tests. Data from these tests, both conducted at NASA Armstrong Flight Research Center, enable a detailed study of atmospheric effects on sonic boom waveforms. The present study expands on previous work [Anderson et al., J. Acoust. Soc. Am. 152, A127 (2022)] by analyzing more booms with additional statistical analyses including metric distributions, standard deviations, and confidence intervals. Results from CarpetDIEM indicate that the confidence interval widths of mean metric levels computed across a seven-microphone array spanning 122 m vary by 1-5 dB, depending on the loudness metric. The effects of peak clipping are also considered, and an analysis is conducted to determine how to best recover from peak clipping for different metrics. [Work supported by NASA Langley Research Center through the National Institute of Aerospace and Analytical Mechanics Associates.]
Machine learning for acoustic sensing in challenging environments
Authors: Greenhall John
Published: November 2023

Acoustic measurements provide unique capabilities that make them attractive for a wide range of monitoring, characterization, and classification applications where other sensing techniques based on electromagnetic waves or radiography have physical limitations. One of the main challenges in real-world applications of acoustic sensing is the information-rich nature of the measurements. These measurements contain vast amounts of information about the system being investigated, but it can be difficult to extract the useful aspects of the data from the complex raw data. Thus, machine learning (ML) techniques have been gaining popularity rapidly in acoustics, by identifying complex correlations in the measurements that are not apparent from traditional techniques. In this presentation, I focus on performing acoustic measurements in challenging environments, where data is highly complex and/or noisy. I discuss how ML can be applied to the main categories of acoustic data, i.e., time-series, frequency-spectra, and numeric features, and provide examples where each category is useful in a different challenging environment, such as in materials with thermal gradients, multi-component systems with complex vibrational coupling, and in fast-moving streams of flowing biomass.
Resonant ultrasound spectroscopy of hybrid metal additive manufacturing
Authors: Ley Jazmin , Pantea Cristian , Greenhall John , Turner Joseph A.
Published: November 2023

Additive manufacturing has been targeted as the next high-impact fabrication technique for parts and components. Hybrid metal additive manufacturing (AM) refers to the 3-D printed fabrication process involving secondary manufacturing processes or energy sources and multifunctional printing. Specific layers are altered within the build using additional processes (i.e., milling or peening) that are synergistic with the additive process. This combination alters the sample microstructure and can refine grains, increase dislocation density, or induce residual stresses. The effect of these hybrid layers is typically not confined within the layer alone but has a compounding effect on preceding layers. The goal is to control the changes in print parameters throughout the build to enhance component performance, but unique challenges remain for nondestructive validation of such samples. Traditional ultrasonic methods on hybrid-AM components have successfully mapped material variations with sufficient spatial resolution. However, the use of resonance ultrasound spectroscopy (RUS) for hybrid-AM is less developed. In this presentation, the use of RUS is described relative to the characterization of hybrid AM 316L stainless steel samples. The spatial organization of the hybrid samples affects the resonances relative to their mode shape. Computational models are used to quantify the impact of the hybrid processes.
Visual speech benefit provided by realistic sentences in noise
Authors: Ibrahim Ronny , Miles Kelly , Derleth Ralph Peter , Buchholz Joerg M.
Published: November 2023

Understanding speech in background noise presents a significant challenge to listeners with hearing loss. Even though hearing aids are very successful in restoring listening in quieter conditions, current devices provide only limited benefit in noise. While seeing a talker can improve intelligibility, visual benefit has typically been quantified using rather unrealistic audio-visual speech materials. Here, we investigated visual benefit using realistic effortful speech from the ECO-SiN corpus. Audio-only, audio-visual, and visual-only sentences were presented in three simulated real-world environments at their realistic sound levels in a 3-D loudspeaker array equipped with integrated high-resolution video projectors. Ten young normal-hearing (NH) listeners as well as 18 older listeners with sensorineural hearing loss participated in the experiment with and without their own hearing aids. While the NH listeners rapidly hit ceiling, listeners with hearing loss struggled to understand the audio-only sentences in the louder background noise—even when aided. There was, however, demonstrable visual benefit of up to 16% in the audio-visual condition for both groups, which is significantly less than commonly reported. Future research will explore if the individual outcomes of the audio-visual ECO-SIN test better reflects real-world hearing experience and how far this is maintained when using virtual reality glasses.