bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic radiation force optical coherence elastography for ocular biomechanics
Authors: Larin Kirill
Published: November 2021

The mechanical properties of the cornea, limbus, and sclera provide important information regarding eye health. Optical coherence elastography (OCE) is highly suitable for assessing ocular tissues' mechanical properties due to its high resolution and superior displacement sensitivity. Typically, elastography involves an external mechanical excitation of the tissue. We recently adopted a method of Air-Coupled Acoustic Radiation Force for the generation of elastic waves in ocular tissues. This method shows several clear advantages other than the traditionally used air-puff excitation. However, the safety of this method needs to be studied before its clinical applications. Also, there is increased interest in passive elastography, where the mechanical response to natural physiological forces like heartbeat and respiration is measured. I will also demonstrate examples of using heartbeat for quantification of tissues' mechanical properties in vivo.
Multi-level parallelism for structural acoustic uncertainty quantification
Authors: Wixom Andrew S. , Myers Kyle , Shepherd Micah
Published: November 2021

Uncertainty quantification (UQ) of structural acoustic systems is currently of great interest and is expected to only become more prevalent in the future. Techniques such as generalized polynomial chaos, Gaussian metamodeling, and others allow a variety of UQ analyses to be performed by forming a surrogate model of the system of interest using only "blackbox" evaluations of the system and do so with a much reduced number of evaluations compared to the Monte Carlo method. However, to properly resolve the complicated behavior of acoustic or vibratory systems, and in particular how the uncertainty affects that behavior, this can still take a large number of system evaluations even when using these advanced UQ techniques. This work focuses on the tradeoffs between parallelizing the UQ method compared to the structural-acoustic blackbox and how a variety of implementation choices affect the run-time on high performance computing resources. Example problems with differing system sizes are used to demonstrate interesting features.
Multi-user interactive systems for immersive virtual environments
Authors: Chabot Samuel , Mathews Jonathan , Braasch Jonas
Published: November 2021

Human-scale immersive spaces are increasingly prevalent in real-world contexts as viable applications for large-scale displays, speaker arrays, and reactive platforms continue to be discovered. One of the primary challenges hindering adoption of these modalities is the integration of intuitive interaction frameworks, allowing individuals in the space to engage naturally with the environment. In the Collaborative Research-Augmented Immersive Virtual Environment, or CRAIVE-Lab, at Rensselaer Polytechnic Institute, we have integrated a variety of technologies to foster natural engagement with the space. We developed a dynamic display environment to enable user-specific contribution to and control of the virtual space. In addition, we installed a sensor network consisting of both video and audio sensor arrays to provide fused location data and voice activity detection for each user in the space without body-worn devices. Integration of these technologies into the environment facilitates an immersive experience by fostering natural interaction between an individual and the lab system.
Steelpan fundamental frequency estimation through audio feature extraction and deep neural networks
Authors: Malloy Colin
Published: November 2021

The estimation of fundamental frequency, or pitch, is a fundamental task in computational audio analysis with a variety of applications. Steelpan audio has proven difficult for general pitch detection methods CRéPE and pYin. CRéPE is a method that uses a deep convolutional neural network to perform pitch estimation directly from the audio signal while pYIN is a digital signal processing-based approach. Audio feature extraction is the process of using digital signal processing techniques to extract low level audio information from signals. Combining audio feature extraction with logistic regression is currently the best performing steelpan pitch estimation method, but the efficacy of using deep neural networks in lieu of traditional machine learning algorithms has yet to be determined. This paper compares the performance and computational requirements of a deep neural network-based architecture against logistic regression as well as the established pYIN and CRéPE pitch detection methods to determine which method is the most accurate and efficient. All of these methods are evaluated on a test dataset containing one-hit audio samples from several distinct sounding steelpans. Generalization to other steelpans is assessed by including samples in the test dataset from steelpans for which no samples are in the training dataset.
Insights into heated, supersonic jet noise gained from writing a review article on launch vehicle noise
Authors: Lubert Caroline P. , Gee Kent L. , Tsutsumi Seiji
Published: November 2021

At the time of writing this abstract, a review article is being finalized for publication in JASA entitled a “Supersonic jet noise from launch vehicles: 50 years since NASA SP-8072,” it describes the current state-of-the-art in rocket and launch vehicle noise research, including how highly heated, supersonic rocket plumes differ from other jets, the origin and nature of the radiated sound from both free and impinging rocket plumes, and techniques for pad noise mitigation during rocket launches. Existing and candidate methods (both empirical and numerical) for modeling rocket launch noise are reviewed, including the ubiquitous NASA SP-8072 methodology, which has formed the cornerstone of many rocket launch noise prediction models over the past half century. This talk will briefly discuss some of the insights gained as a result of writing this review and show how they led to the inevitable conclusion that an entirely new approach to rocket plume noise modeling—one that incorporates the underlying physics of the noise generation mechanisms—must be pursued.
Initial performance analysis of an array of low-cost infrasound sensors with 43 elements
Authors: Frazier Garth , Talmadge Carrick , Waxler Roger M. , Buchanan Hank , Audette William (Chip) , Brooks Chris
Published: November 2021

Many infrasound sensor arrays are limited in the number of elements because of the cost of individual sensors. While some of these sensors are of exceptional quality and have calibrated (amplitude and phase) response to frequencies below 0.01 Hz, not all infrasound sensing applications require this degree of accuracy and precision. Moreover, to achieve significant reduction of the influence of wind noise at infrasound frequencies below 1 Hz requires large and/or complex mechanical wind screen apparatus. There are applications for which the benefits of having a so-called “large-N” array of lower cost, lower performance sensors outweigh the benefits of very high performance sensors. These benefits include wind noise reduction without large windscreens and the ability to resolve several acoustic sources simultaneously. This presentation will present preliminary array processing performance results from the deployment of an array of 43 recently developed, experimental low-cost infrasound sensors.
PLetma—Parallel software package for intensive infrasound simulation
Authors: Khodr Codor , Dragna Didier , Blanc-Benon Philippe , Marchiano Régis , Aubry Ludovic , Gainville Olaf , Millet Christophe
Published: November 2021

The Plateform of the Laboratory of Studies and Modeling in Acoustics (PLetma) is a suite of scientific softwares developed by the partner institutions of LETMA since 2015. Currently under development, it contains four different models, namely 3D ray-tracing, 3D non-linear one-way equation, 3D normal modes and 2D direct Navier–Stokes, as well as user interfaces for model execution and data visualization. The aim of this package is to provide a set of complementary tools for the modeling of broadband infrasound signals in a moving inhomogeneous atmosphere. It allows to cover a large panel of low-frequency propagation problems arising in geophysics or engineering. Implemented with MPI and OpenMP, the package relies on parallelism to improve computational efficiency of simulations. PLetma provides the infrastructure for incorporation of existing propagation and variability modeling capabilities. Comparisons between the four methods have been successfully undertaken on a test case [Sabatini et al., JASA (2016)]. Sensitivity analyses have been conducted to understand the effect of environmental parameters on modeling of long-range infrasound propagation. [This work was conducted within the framework of LETMA (Laboratoire ETudes et Modélisation Acoustique), a Contractual Research Laboratory shared between CEA, CNRS, Ecole Centrale de Lyon, C-Innov, and Sorbonne Université.]
The neural processing of sound in infants
Authors: Lau Bonnie K. , Taulu Samu , Kuhl Patricia K. , Lee Adrian KC
Published: November 2021

Early auditory abilities play an important role in infants’ ability to acquire language, appreciate music, and navigate the complex acoustic environments around them. However, the neural mechanisms that support infant sound processing are not well understood. This study used magnetoencephalography (MEG) with recent advancements in movement compensation to obtain functional measures of auditory processing in awake infants. MEG responses were recorded longitudinally at 3, 6, and 11 months of age to an English bi-syllabic word and an amplitude-modulated complex tone as a non-speech but spectro-temporally complex control stimulus. MEG recordings were made with an Elekta Neuromag® whole-head 306-channel MEG system. The neural generators of the MEG signals were determined using an equivalent current dipole (ECD) model. High quality MEG data with good signal-to-noise ratios were recorded in infants as young as 3 months of age in both conditions. ECD field maps showed focal sources in the brain confirming the ECD model is a robust source localization approach that can fit auditory neural sources in infants. Our results show that dipole modeling of MEG signals in combination with advanced movement compensation offers a temporally precise method of investigating how the cortical processing of sound changes across the first year of life.
Laminar specificity of the auditory awareness negativity under multitone masking: A biophysical modeling study
Authors: Fernandez Pujol Carolina , Blundon Elizabeth , Dykstra Andrew R.
Published: November 2021

Electroencephalography (EEG) and magnetoencephalography (MEG) are excellent mediums for capturing human neural activity on a millisecond time scale, yet little is known about their underlying laminar and biophysical basis. Here, we used a reduced but realistic cortical circuit model—Human Neocortical Neurosolver (HNN)—to shed light on the laminar specificity of brain responses associated with auditory conscious perception under multitone masking. HNN provides a canonical model of a neocortical column circuit, including both excitatory pyramidal and inhibitory basket neurons in layers II/III and layer V. We found that the difference in event-related responses between perceived and unperceived target tones could be accounted for by additional input to supragranular layers arriving from either the non-lemniscal thalamus or cortico-cortical feedback connections. Layer-specific spiking activity of the circuit revealed that the additional negative-going peak that was present for detected but not undetected target tones was accompanied by increased firing of layer-V pyramidal neurons. These results are consistent with current cellular models of conscious processing and help bridge the gap between the macro and micro levels of analysis of perception-related brain activity.
Experimental characterizations of band gaps in 3D printed phononic materials
Authors: Matlack Kathryn
Published: November 2021

Phononic materials contain spatial periodicity of material properties or geometry, which cause band gaps and other unnatural wave phenomena to form. While these behaviors have been well studied theoretically and experimentally in representative systems, the growth of 3D printing caused a surge of phononic materials to be physically realized and studied in the last several years. Since 3D printing enables almost any geometry to be fabricated in a variety of materials, it opens the possibility for band gaps to be used for frequency-targeted vibration mitigation designed directly into structural components. This talk presents our recent work on 3D printed phononic materials with tailored vibration mitigation, focusing on experimental characterizations of band gaps. Two phononic materials will be discussed: (1) lattice-resonator metastructures, that combine a 3D printed lattice with embedded masses to form band gaps that depend on lattice geometry; and (2) radial phononic materials, that combine radially-dependent properties with periodicity to form band gaps for radially-propagating torsional waves. Experimental intricacies will be highlighted, including material damping, fluid–structure interactions within the band gap, and isolating modes and wave polarizations. Such thorough experimental characterizations of band gaps in phononic materials enable the development of robust and predictive modeling and design capabilities.
Resonant ultrasound spectroscopy for anisotropic materials with misaligned geometric and material axes
Authors: Beardslee Luke , Remillieux Marcel , Ulrich Timothy J.
Published: November 2021

Resonant ultrasound spectroscopy (RUS) is a powerful non-destructive technique used to measure the full elastic tensor of a material. The original formulation of this technique has restrained its application to relatively simple situations in which the sample has a trivial geometry (e.g., cube, cylinder, sphere), is made of one material only, with perfect alignment of material and geometric axes. In many practical applications, these ideal conditions cannot be met. Recently, RUS has been enhanced by the authors to handle these more complex systems by combining the finite-element method with a genetic algorithm. The capabilities of this new RUS approach are demonstrated experimentally using both a non-uniform hemisphere and a cylindrical sample made of compressed particles. The particular manufacturing process of the cylindrical part results in a sample with anisotropy and a misalignment of the geometric and material axes. Although the sample has a simple geometry it consist of a complex material. Confidence in the RUS inversion process is assured by a careful comparison of the mode shapes measured experimentally and simulated with the proper material orientation and elastic tensor.
Measurement of frequency-dependent shear properties of highly compliant materials using Kibble’s method
Authors: Vlajic Nicholas , Beck Benjamin , Coughlin Christopher
Published: November 2021

We present a method to determine the frequency-dependent properties of highly-compliant materials by measuring the response of rod-like specimens subjected to an applied torque. Kibble’s method, which utilizes a velocity measurement and two electrical measurements, is used to calculate the applied torque on the specimen as a function of frequency. Shear modulus and loss factor in shear are determined by fitting mechanical models to transfer functions between the applied torque and torsional response of the sample. We demonstrate this technique on a prototype apparatus using different polymer materials and specimen geometry. Estimates of the shear modulus and loss factor in shear are determined over a range of frequencies that include the first six torsional resonant modes. These material properties are compared with data obtained using a commercial Dynamic Material Analyzer wherein the samples are excited in a bending mode.
Development of a water-filled four-sensor impedance tube
Authors: McNeese Andrew R. , Wilson Preston S. , Haberman Michael R. , Lee Kevin M.
Published: November 2021

Four-sensor impedance tubes are readily utilized for characterization of the acoustic properties of materials in a gaseous host medium, as described in the standard ASTM E2611-19. Similar acoustic characterization is desired for materials submersed in water. Previous studies have documented the challenges of performing measurements in water-filled impedance tubes due to interaction with the elastic tube wall and difficulty in obtaining a suitable end-termination condition. Building upon previous demonstration of a two-sensor water-filled impedance tube [J. Acoust. Soc. Am. 113, 3245 (2003)], this paper discusses the development and demonstration of a four-sensor water-filled impedance tube with an anechoic termination. The technique utilizes two sensors on each side of the test section to simultaneously characterize both the incident and transmitted standing wave field and extract the complex impedance and wavenumber from the test sample. Discussion will focus on the challenges of performing such measurements in a water-filled tube along with methods for overcoming these challenges. Validation measurements of homogeneous materials in the 1–10 kHz band will be presented to demonstrate that both the complex impedance and wavenumber of a material submersed in water can be extracted using this approach. [Work supported by ONR.]
Articulatory and acoustic analysis of voice acting
Authors: Feehan Colette
Published: November 2021

Voice actors are an under-utilized population for linguistic study. Looking at voice actors' novel productions of typical speech sounds can tell us more about over which muscles we have volitional control. This can help test models of speech production, inform speech therapy, and create better pedagogy for teaching vocal performance. While there have been several studies analyzing the acoustics produced by voice actors (Teshigawara, 2001; 2003; 2004; 2009; 2011; Teshigawara et al., 2007; Uchida, 2007) there are fewer studies that have investigated the articulation of voice acting (Teshigawara & Murano, 2004). This study used acoustic analysis, 3D ultrasound, and electroglottography to investigate the speech produced by six professional and amateur voice actors (2 female, 4 male). Measures of average fundamental frequency (F0) and F0 range were collected from each actor speaking in their regular adult voice and a simulated child voice. 3D ultrasound was used to look at tongue placement and horizontal kymograms of the ultrasound images were also used to infer hyoid bone movement. Additionally, acoustic estimates of vocal tract length were compared to electroglottography measurements of laryngeal raising for two of the subjects. This presentation will describe the within-subject variation across each actor’s adult and simulated child voices.
Effect of vocal tract morphology on tongue shaping for American English /ɹ/
Authors: Lu Yijing , Hsu Haley , Goldstein Louis , Toutios Asterios
Published: November 2021

There is a lack of general agreement among previous studies (e.g., Bakst, 2016; Dediu & Moisik, 2019; Westbury et al., 1998) on whether measurements of vocal tract morphology are robust predictors of inter-speaker variation in tongue shaping for American English /ɹ/. One possible reason is the different quantifications of /ɹ/ tongue shapes that were employed. The current study compares the relationships between a single set of anatomical measurements and three different measures of lingual articulation for /ɹ/ in /ɑɹɑ/ in midsagittal real-time MRI data. A novel method was developed to quantify the palatal constriction location and length, which served as the first two measures of tongue shape. A linear Support Vector Machine divided the constriction location and length measures into regions that approximate the visually identified categories of “retroflex” and “bunched.” The third shape measurement is the signed distance of each token of /ɹ/ to the division boundary, representing the degree of “retroflexion” or “bunchedness” based on palatal constriction properties. These three measures showed marginally to moderately significant linear relationships with two specific measures of individual speakers’ vocal tract anatomy: the degree of mandibular inclination and the length of the oral cavity roof. Overall, the effect of anatomy on the lingual articulation of /ɹ/ is not strong. [Work supported by NSF, Grant 1908865.]
Velopharyngeal opening in French: Revisiting velum configuration in nasal, oral, and rest intervals
Authors: Islam Md Jahurul , de Boer Gillian , Gick Bryan
Published: November 2021

Velopharyngeal Opening (VPO) is associated with nasality in speech. Earlier studies on French suggested that there is a continuum of VPO: nasal vowels, nasal consonants, contextually nasalized vowels and, finally, oral segments. However, most of these studies used isolated words/syllables, very small numbers of participants, and/or indirect measures of the VPO. In this study, we tested whether the predictions from the previous studies extend to sentence-level speech with a substantially larger speech sample drawn from more participants using a more direct measurement of the VPO. Using the Université Laval X-ray videofluorography database containing speech from nine Quebecois French speakers, the VPO was measured for speech segments and rest positions. Results indicate that VPO was greatest during between-utterance intervals, followed by (in descending order) phonemically nasal segments, contextually nasalized segments, and oral segments. Contrary to previous suggestions of differences of VPO in nasal segments, no difference was found between nasal vowels and nasal consonants suggesting that such classification is not necessary (and the traditional binary [±nasal] feature still holds). Furthermore, in contrast to previous reports, anticipatory nasalization was found to have greater VPO than carryover nasalization.
The Non-Native Articulatory corpus—French: An ultrasound corpus of French as an additional language
Authors: Chanethom Vincent , Masella Soldati Giulia , Todd Haley A. , Brennan Hannah M. , Myers Jaxon V. , Hannon Dominique A. , Yaghmour Brenna J. , Kwon Harim
Published: November 2021

We present a new corpus of spoken French, the Non-Native Articulatory corpus (NNA)—French, which is being made available to the research community. The NNA—French is a collection of simultaneous ultrasound and audio recordings produced by French speakers from various linguistic backgrounds, including both native and nonnative speakers of the language. Each speaker read a list of 60 short sentences in French, and the acoustic signals and the mid-sagittal ultrasound images of the tongue movement (∼80 fps) were simultaneously recorded. Speakers also completed a comprehensive language background questionnaire. Each speech sample is presented with the speaker’s demographic information (gender, age, birth place), language background (native language, any additional languages spoken), and French experience and proficiency. The articulatory information from the ultrasound images allows various types of phonetic research, such as comparing French speakers from diverse background, investigating articulatory strategies used by learners of French, and examining phonological development of French learners at different proficiency levels. The NNA—French continues to grow and we expect it to be a valuable resource for researchers in the field of phonetics and second language learning, as well as for French language instructors.
Contribution of vocal fold thickness to gender perception
Authors: Zhang Zhaoyan , Kreiman Jody , Zhang Jason
Published: November 2021

Male vocal folds are often longer and thicker than female vocal folds. The length difference is generally considered responsible for the notable difference in fundamental frequency between men and women, which plays an important role in gender perception. The role of the thickness difference in gender perception is less clear, although our recent studies demonstrated an important role of thickness in the control of voice quality. The goal of this study is to investigate the contribution of changes in vocal fold thickness and stiffness to gender perception. Synthetic voices were generated using a three-dimensional vocal fold model with parametric variations in vocal fold geometry, stiffness, adduction, and subglottal pressure. The vocal tract was kept constant in order to focus on the contribution of the voice source. Listening subjects were asked to judge speaker gender in a multiple choice task. Preliminary results showed a significant effect of vocal fold thickness and transverse stiffness on gender perception, with voices produced by thicker vocal folds and lower transverse stiffnesses more likely to be judged as male. Acoustically, gender perception scores were correlated with the fundamental frequency and spectral shape. [Work supported by NIH.]
On the significance of three-dimensional imaging for interpreting vocal fold dynamics
Authors: Berry David
Published: November 2021

Physical mechanisms of regular and irregular vocal fold vibration were first studied in a finite element model of vocal fold vibration using the method of empirical eigenfunctions. Later the same method was used to successfully study physical mechanisms of vocal fold vibration in laboratory hemilarynx experiments (in which the medial surface of vocal fold was imaged). In subsequent clinical studies, however, the method exhibited significantly less interpretive power, presumably because of the limitations imposed by imaging from a 2D superior view. Our hypothesis is that the interpretive power of the method of empirical eigenfunctions will be significantly enhanced in clinical settings if 3D imaging is used instead of 2D imaging. To test this hypothesis, the method of empirical eigenfunctions was employed on the same finite element model implemented previously, as dynamical information was systematically removed from the analysis (interior tissue dynamics, medial surface dynamics, vertical dynamics of the superior surface, etc.). The natural modes of vibration were re-computed at each stage, and the deformations from the original natural modes were observed. The results suggest that in clinical settings, the method of empirical eigenfunctions retains significant interpretive power regarding physical mechanisms of irregular vibration when 3D imaging is used.
Elastography of a gelatin M5 model mimicking the true vocal folds
Authors: Lamprecht Raphael , Scheible Florian , Semmler Marion , Sutor Alexander
Published: November 2021

The material properties of the vocal folds play an important role in phonation, but are also of interest for basic research. In the diagnosis of e.g. vocal fold palsy ultrasound is still an emerging technology. Ultrasound elastography, a technique measuring the tissue stiffness, is widely employed in the diagnosis of e.g. liver fibrosis and thyroid nodules. Using a quasi-static approach, this technique can also be applied to the vocal folds, improving the understanding of their biomechanical properties and, in the future, the diagnosis of pathological changes in the vocal folds. We use a gelatin phantom of the vocal folds, modeled after the well-known M5 model of the true vocal folds and augmented with additional material that mimics the surrounding tissue. The phantom is compressed with an ultrasound transducer (central frequency of 15 MHz) in the inferior direction, with the image plane in the frontal plane. Ultrasound images of the compression process and the acting force are recorded. Based on this information, a developed elastography algorithm evaluates the data. The results of the experimental setup are compared with simulation results generated using FEBio, a software specialized in tissue simulation.
Incomplete acoustic time reversal, frequency shifting, and matched field processing
Authors: Dowling David R.
Published: November 2021

In a reciprocal time-invariant medium, sound can travel in both directions along acoustic paths. This bi-directionality enables acoustic retrofocusing via time reversal (TR) and acoustic source localization via matched field processing (MFP). Given this common basis, the simplest frequency-domain formulations of acoustic TR and MFP are essentially identical; both involve a quadratic product of forward- and backward-propagating complex fields. For this presentation, all scenarios begin with the acoustic field from a remote source that propagates forward through a potentially-complicated acoustic environment to a transducer array where it is recorded. The difference between TR and MFP then arises because the second backward-propagating (time-reversed) acoustic field may be (i) a genuine field in the actual environment as in acoustic TR, or (ii) a predicted field developed from a model of the environment as in MFP. This presentation describes a third possibility, frequency-difference MFP or incomplete acoustic TR, that combines (i), (ii), and a multiplicative property of harmonic plane waves to produce frequency-downshifting. The resulting unconventional formulation involves a cubic product of complex fields and allows robust reduced-resolution source localization with sparse arrays in complicated uncertain environments. Example results from simulated, laboratory, and ocean propagation data are shown. [Sponsored by ONR, NAVSEA, NSF].
Passive time-reversal mirror for acoustic characterization of the seabed
Authors: Godin Oleg A. , Tan Dexter , Tan Tsu Wei
Published: November 2021

This paper investigates application of a signal processing technique, which is motivated by time reversal, to geoacoustic inversions in a shallow-water waveguide. The signal processing mimics operation of a physical time-reversal mirror. The input data for the simulated time-reversal mirror can be obtained using either a compact, broadband sound source or cross-correlation of the diffuse noise recorded by spatially separated receivers. Low-frequency sound propagation is considered over ranges that are large compared to the water depth. The approach exploits the notion that the “best” focusing of the backpropagated time-reversed signal occurs at the “right point,” when the backpropagation takes place in the same propagation medium as the one, where the data have been acquired. Various metrics of the focusing quality are considered. A combination of spatial and temporal characteristics of the focus is proposed that leads to a unique solution of the geoacoustic inverse problem for a single-element passive time-reversal mirror. [Work supported by NSF.]
Statistical classification of scatterer ultrasonic signature in bio-mechanical media and spatial localization of digital data using nonlinear time reversal
Authors: Dvorakova Zuzana , Kus Vaclav , Prevorovsky Zdenek , Dos Santos Serge
Published: November 2021

Various nonlinear methods have been investigated in recent years offering improvements of over conventional B-mode in medical imaging and non-destructive testing (NDT) [1], including Nonlinear Elastic Wave Spectroscopy (NEWS) methods. Furthermore, new optimized excitations such as Nonlinear Time Reversal (TR) based methods are classified within TR-NEWS methods [2]. In this context, one of the strategic plan of the international NDT community is to define standards for developing advanced and digitalized automated NDT set-up in modern mass production, defining the concept of NDT 4.0 or NDE 4.0 [3]. In the typical NDE4.0 TR-NEWS equipment, an optimized chirp-coded signal in the range of 0.6–3 MHz is used as a compression coding. The signal classification is performed using the Fuzzy Classification (FC) method and the Divergence Decision Tree (DDT) algorithm using specific $\phi$-divergence spectral measures extracted from the received ultrasonic response containing acoustic nonlinearities. Finally, experimental setup and scatterer classification procedures have been further validated in ondotology with tooth echodentographic experiment where the ultrasonic responses to chirp-coded signals were monitored with a standard Polytec vibrometer, showing the efficiency of TR-NEWS methods for understanding of ultrasonic wave propagation in complex media.
A finite-element based implementation of time-reversal and phase-conjugation acoustic source localization techniques in COMSOL multiphysics
Authors: Mimani Akhilesh , Sartaj Alok
Published: November 2021

In this work, we develop a general working procedure for a finite-element (FE) based implementation of time-reversal (TR) and phase-conjugation (PC) acoustic source localization techniques in COMSOL multiphysics commercial package using its in-built acoustics modules. To this end, a detailed step-by-step algorithm of the forward propagation is presented which includes creation of the computational domain and absorbing boundaries, defining acoustic source(s), meshing, solving, i.e., carrying out a time- or frequency-domain simulation followed by extracting data at virtual microphone array (nodes). The same procedure is used for implementing the TR simulations and frequency-domain PC except that source(s) inside the domain are now deactivated, and time-reversed or phase-conjugated data is enforced at the array nodes, followed by computation of the source map. The test-case of an idealized monopole in a 2D free-space is first considered whereby it is shown that both FE-based TR and PC methods deliver identical results which are in an excellent agreement with a finite-difference time-domain (FDTD) solver results, thereby validating the procedure. Next, the problem of localizing an idealized source in the presence of multiple scatterers and reflections which resemble an urban environment is considered. The COMSOL algorithms are shown to produce satisfactory results which demonstrate the efficiency of commercial FE solvers in handling complex geometries which otherwise tend to become tedious using the traditional FDTD solvers.
Mode-based models with realistic boundary conditions for a laboratory tank
Authors: Terry Kaylyn N. , Vongsawad Cameron T. , Neilsen Tracianne B.
Published: November 2021

A new laboratory water tank at Brigham Young University is being characterized, and a suitable model is needed to describe the sound propagation. Recently, Novak et al. [Acta Acust. Acust., 2018] provided a model for low frequency sound propagation in small tanks with thin walls and Dirichlet boundary conditions. Our goal is to find a model that works at higher frequencies in a large water tank, which includes realistic boundary conditions. These models were specifically made for a rectangular acrylic tank of 3.6 m long by 1.2 m wide with 0.91 m as the maximum depth over a frequency band of 10 Hz to 100 kHz. Solutions to the 3D wave in Cartesian coordinates were used with Dirichlet and Neumann boundary conditions, with key differences noted between transmission loss estimates when realistic boundaries and ideal approximations are used. The models are then updated to include estimates of the characteristic acoustic impedance of the wall material to modify boundary conditions. Each model is sensitive to the number of modes used. The tank sound propagation model will allow us to model our tank with and without anechoic panels, simulate the sound field for optimization problems, and create accurate training data for machine learning applications.
Acoustic characteristics from an in-water down-the-hole pile drilling activity
Authors: Guan Shane , Brookens Tiffini , Miner Robert
Published: November 2021

Sound generated by pile installation using a down-the-hole (DTH) hammer is not well documented and differs in character from sound generated by conventional impact and vibratory pile driving. This paper describes underwater acoustic characteristics from DTH pile drilling during the installation of 0.84-m shafts within 1.22-m steel piles in Ketchikan, Alaska. The median single-strike sound exposure levels measured at 10 m were 138 and 142 dB re 1 μPa2 s for each of the two piles, with cumulative sound exposure levels of 188 and 193 dB re 1 μPa2 s at 10 m, respectively. The sound levels measured at Ketchikan were significantly lower than previous studies, and the sound is determined to be non-impulsive in this study as compared to impulsive in the previous studies. These differences likely result from fact that the DTH hammer used at Ketchikan did not make direct contact with the pile, as had been the case in previous studies. Further research is needed to investigate DTH piling techniques and associated sound-generating mechanisms, and to differentiate the various types of sound emitted.
Effects of nonlinear internal gravity waves on normal-incident reflection measurements of marine sediments
Authors: Chen Tzu-Ting , Lin Ying-Tsong , Chiu Linus Y.-S.
Published: November 2021

Sonar data acquired by sub-bottom profilers and multi-beam echosounder systems are widely used to estimate geoacoustic properties of marine sediments. However, the uncertainty of the seabed property estimates caused by water column variability may limit the application. In this study, we focus on the acoustic focusing and defocusing effects of nonlinear internal waves on normal-incident reflection measurements in the South China Sea. The field experiment was conducted using a transceiver mooring consisted of a sound source and a four channel vertical hydrophone array. The variation of acoustic signal reflections from sub-bottom layers during three days at the same site is observed. The effects of the nonlinear internal waves passing through the transceiver mooring are identified. The impact on the sub-bottom property estimates is investigated. [Work supported by the Office of Naval Research.]
Backscattering by broadside and tilted intermediate thickness empty cylindrical metal shells in water: Experiments and theory
Authors: Hall Bernard R. , Marston Philip L.
Published: November 2021

In prior research the backscattering properties of empty metal shells in water were investigated over a wide frequency range [Morse et al., J. Acoust. Soc. Am. 103, 785–794 (1998); Morse and Marston, J. Acoust. Soc. Am. 111, 1289–1294 (2002)]. The detailed high-frequency features of the observed and modeled enhancements depended on the shell thickness. In the present research backscattering is measured, and modified models are introduced for a steel shell intermediate in thickness between those considered in the aforementioned prior investigations. Some of the outcomes of this investigation may be summarized as follows: (a) for broadside scattering the contribution from a coincidence-frequency related guided wave is easily observed and is prominent within a ray-theory based model; (b) supersonic antisymmetric guided waves are evident at high frequencies; (c) such antisymmetric guided waves also especially result in easily noticed meridional wave backscattering enhancements when the shell is tilted as was previously demonstrated for other tilted shells. [Work supported by ONR.]
Mid-frequency sound transmission in a deep ice-covered ocean at short and medium ranges
Authors: Ivakin Anatoliy N. , Joseph John E. , Reeder D. Benjamin
Published: November 2021

A model of propagation and reverberation in a deep Arctic ocean and a tentative interpretation of ICEX16 data are discussed. The data subset used for analysis was collected by a NPS team in the Beaufort Sea (∼3650 m depth) on 12 March 2016 using mobile EMATT transmitters which were moving under the ice in circular patterns from Ice Camp SARGO that provided various combinations of source-receiver ranges (∼1–10 km) and depths (45–183 m). Transmitted waveforms were sequences of 60 s-long segments comprised of 57 s-long CW pulses at various frequencies (2800, 2900, and 3000 Hz) and 3 s-long 2300–3000 Hz LFM sweeps. Sound speed profiles measured during the experiment showed two shallow ducts, at 0–75 m and 75–250 m water depths. The model developed considers multi-path propagation including multiple reflections and scattering from rough interfaces. The model-based analysis allows examining the spatial and time-frequency structure of recorded arrivals and their sensitivity to variations in water stratification and acoustic parameters of ice and ocean bottom. Preliminary results of the ICEX16 data-model comparisons are presented. Suggestions are considered for environmental measurements to provide necessary inputs and ground-truth for the acoustic model. A potential for enhanced remote sensing capabilities and optimal configurations for future experiments are discussed. [Work supported by ONR.]
Architectural acoustics continuing education course—Presenter registration and reporting
Authors: Good Kenneth W.
Published: November 2021

The Technical Committee on Architectural Acoustics (TCAA) is a Registered Provider in the American Institute of Architects (AIA) Continuing Education System (CES). The TCAA has developed a standardized introductory short course for architects called “Architectural Acoustics,” for which attendees can earn one continuing education unit (CEU). This paper will cover the administrative requirements of the ASA/CES, to prepare potential presenters. These requirements include the proper handling of paperwork so that AIA members may receive credit for the course. The manner in which the course is given is also dictated by AIA requirements. TCAA membership and attendance at this workshop are required to qualify as an authorized presenter for this AIA/CES short course. Of course, anyone is free to register with the AIA to provide their own CEU program. However, the advantages of participating in this program are that the TCAA short course is already prepared, it is pre-approved by the AIA, and the registration fees are paid by the Acoustical Society of America.
Fin whale localization and environmental inversion using modal arrivals of the 20-Hz pulse
Authors: Amaral Jennifer L. , Miller James H. , Potty Gopu R. , Lin Ying-Tsong , Vigness-Raposa Kathleen J.
Published: November 2021

Fin whale doublet calls, described as two 20-Hz pulses recorded at different interpulse intervals, have been attributed to the whale's calling behavior, however they could also result from acoustic mode propagation effects. Modes travel with their own frequency-dependent group velocities. The dispersion of these modes results in the sound being recorded as multiple arrivals on a receiver. Multiple modal arrivals of 20-Hz fin whale calls were recorded, with mode one arriving after mode two. The time delay between modal arrivals varied throughout the recording and is range dependent. The range dependency of this time delay was used to estimate the range of the whale from individual hydrophones by determining the modal group velocities that resulted in the observed delays. A pair of hydrophones was used to localize the whale for the duration of time when two modes were detected. The KRAKEN normal mode model was utilized in an inversion scheme to determine the compressional wave speed and depth-to-bedrock in the study area that supported the estimated modal group velocities. The inversion resulted in a depth-to-bedrock of 200 m and compressional wave speed of 1735 m/s, which were supported by measurements reported in literature for nearby regions. [Work supported by BOEM.]
A sound resolution to the food paradox in the sea
Authors: Benoit-Bird Kelly
Published: November 2021

The average concentrations of biota in the ocean are generally low, presenting a critical problem for ocean consumers. In seminal experimental work in the 1970s, Lasker demonstrated that animals fed the average food concentrations measured using nets and pumps do not survive, presenting a paradox for life in the sea. Active acoustics, in contrast to more traditional tools, allow us to sample a wide range of animals at high spatial and temporal resolution. Employing a variety of platforms including ships, profilers, moorings, and autonomous vehicles to deploy acoustic sensors, often guided by the predators themselves, we find that instead of being relatively devoid of life, the ocean is peppered with narrow hot spots of activity. These features, often missed with traditional sampling tools, exist from the surface ocean to the deep sea, the tropics to the poles, in animals ranging from plankton and fish to squid and whales. These small patches of plenty have impacts on ecosystems disproportionate to their contribution to the total biomass. Small aggregations provide the key to solving experimentally demonstrated feeding paradoxes as well providing a mechanism for evolution in an apparently isotropic environment where there are no obvious barriers to gene flow, Hutchinson’s “Paradox of Plankton.”
Plane-wave ultrasound assessment of ocular blood flow in preeclampsia and correlation with optical coherence tomography angiography
Authors: Silverman Ronald H. , Bearelly Srilaxmi , Urs Raksha , Ketterling Jeffrey A. , Wapner Ronald
Published: November 2021

We examined both eyes of 58 post-partum subjects within 72 hours of delivery with plane-wave ultrasound and optical coherence tomography angiography (OCTA). 8 had preeclampsia (PE), 21 severe PE (sPE). 9 chronic or gestational hypertension and 21 were controls. We performed plane-wave ultrasound with a Verasonics Vantage-128 and L22-14vXLF 18 MHz linear array, acquiring 3-angle compound images of the region of the optic nerve and choroid at 6 kHz for 3 s. Data were post-processed to obtain pulsatile flow characteristics of the central retinal artery and vein, the short posterior ciliary arteries and the choroid. Ultrasound revealed significantly elevated blood flow velocity and reduced resistance in sPE compared to controls. Spectral domain OCTA images were acquired with a Zeiss Plex Elite immediately before or after ultrasound. We analyzed 6x6 images centered on the macula and optic nerve to determine vascular density of the superficial and deep retina, and 3 i 3 images centered on the macula to determine foveal avascular zone area and vascular density of the choriocapillaris. Comparison of ultrasound with OCTA findings revealed significant correlations between flow velocity and resistance with vascular density in the superficial retina and choriocapillaris. These findings demonstrate a relationship between functional (ultrasound flow) and structural (OCTA vascular density) parameters in the eye, and especially in the choriocapillaris which we hypothesized would play role in the reduced flow resistance observed in sPE.
Automated in vivo detection and localization of posterior staphyloma in ultrasound b-modes
Authors: Lye Theresa H. , Ito Kazuyo , Yu Daryle Jason G. , Dan Yee Shan , Loh Isabella Q. , Silverman Ronald H. , Hoang Quan V. , Mamou Jonathan
Published: November 2021

In high and pathologic myopia eyes, staphyloma, an outpouching of the eyewall, is associated with risks of permanent vision loss. Automated detection of staphyloma in ultrasound B-modes could assist clinicians in quickly identifying patients at risk. In this study, an algorithm to detect the presence of staphyloma and locate the staphyloma apex was developed. A 10 MHz ultrasound probe was used to acquire 127 B-modes, from 82 eyes and 52 patients. Sixty-one of the B-modes included staphyloma, as determined by an experienced ophthalmologist who also marked the staphyloma apex in each image where present. In each B-mode, the vitreoretinal boundary was automatically detected by a thresholding method. The local radius of curvature (K) was computed, and the ability of the standard deviation of K to detect staphyloma was evaluated by receiver-operating characteristic analysis. The staphyloma apex was automatically detected as the point on the vitreoretinal boundary furthest from the center of the transducer. The area under the curve using standard deviation of K for staphyloma detection was 0.927. The average error in detected staphyloma apex location was 1.34 ± 1.36 mm. These results demonstrate the potential of automated staphyloma detection and localization from ultrasound, which could assist in quick diagnosis of staphyloma.