bluuebunny/crossref_metadata_2025 huggingface dataset:
The diagnostic accuracy of saliva testing for SARS‐CoV‐2: A systematic review and meta‐analysis
Authors: Atieh Momen A. , Guirguis Marina , Alsabeeha Nabeel H. M. , Cannon Richard D.
Published: June 2021

Introduction

Early detection of coronavirus disease 2019 (COVID‐19) is paramount for controlling the progression and spread of the disease. Currently, nasopharyngeal swabbing (NPS) is the standard method for collecting specimens. Saliva was recently proposed as an easy and safe option with many authorities adopting the methodology despite the limited evidence of efficacy.

Objectives

The aim of this review was to systematically evaluate the current literature on the use of saliva test for detecting severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) and carry out a meta‐analysis to determine its diagnostic accuracy.

Materials and methods

Prospective studies were searched for in electronic databases, complemented by hand‐searching relevant journals. The risk of bias and applicability were assessed using the revised Quality Assessment of Studies of Diagnostic Accuracy Studies (QUADAS‐2) tool. Meta‐analyses and meta‐regression modeling were performed to calculate the diagnostic accuracy and examine sources of heterogeneity.

Results

A total of 16 studies were included with 2928 paired samples. The overall meta‐analysis showed a high sensitivity and specificity for saliva test at 0.88 (95% CI 0.82–0.92) and 0.92 (95% CI 0.75–0.98), respectively. The diagnostic odds ratio was calculated at 87 (95% CI 19–395) and area under the curve was calculated as 0.92 (95% CI 0.90–0.94) suggesting very good performance of the saliva tests in detecting SARS‐CoV‐2.

Conclusion

Saliva testing has a very good discriminative and diagnostic ability to detect of SARS‐CoV‐2. Additional large and well‐designed prospective studies are needed to further validate the diagnostic accuracy and determine a safe sample collection method prior to its recommendation for mass application.

Clinical relevance

Saliva demonstrated high sensitivity and specificity. The use of saliva will allow for self‐collection of specimens and specimen collection in outpatient and community clinics.
A Machine Learning Framework for Decision Support in Design and Manufacturing
Authors: Balu Aditya , Ghadai Sambit , Young Gavin , Sarkar Soumik , Krishnamurthy Adarsh
Published: June 2021

The widespread adoption of computer-aided design (CAD) and manufacturing (CAM) tools has resulted in the acceleration of the product development process, reducing the time taken to design a product [46]. However, the product development process, for the most part, is still decentralized with the design and manufacturing reviews being performed independently, leading to differences between as-designed and as-manufactured component. A successful product needs to meet its specifications, while also being manufacturable. In general, the design engineer ensures that the product is able to function according to the specified requirements, while the manufacturing engineer gives feedback to the design engineer about its manufacturability. This iterative process is often time consuming, leading to longer product development times and higher costs. Recent researches in integrating design and manufacturing [24, 28, 46] have tried to reduce these differences and making the product development process easier and accessible to designers, who may not be manufacturing experts. In addition, there have been different efforts to enable a collaborative product development process and reduce the number of design iterations [8, 10, 41]. However, with the increase in complexity of designs, integrating the manufacturability analysis within the design environment provides an ideal solution to improve the product design process.
Advances in Computer Aided Engineering for Gas Turbine Research and Development
Authors: Vilag Valeriu , Vilag Jeni , Cuciumita Cleopatra
Published: June 2021

Gas turbines represent energetic machines that operate following the Brayton thermodynamic cycle [6], [16] creating mechanical power and/or thrust. The majority of them use atmospheric air as working fluid but some are working in a closed loop with either air, carbon dioxide or other convenient gas. The main parameters defining the cycle are the combustion temperature and the overall pressure ratio [20]. In principle, the higher the combustion temperature is, the higher the efficiency of the entire gas turbine will be and, for a chosen value of the combustion temperature an optimum overall pressure ratio exists [29]. The main components of the gas turbine are:
Mesoscale Lattice Structure Design and Simulation with the Support of a Property Database
Authors: Dong Guoying , Tang Yunlong , Fiona Zhao Yaoyao
Published: June 2021

The lattice structure is a type of cellular materials [1] that has truss-like structures with interconnected struts and nodes in a three-dimensional (3D) space. Compared to other cellular materials such as random foams and honeycombs, the lattice structures exhibit better mechanical performance [2]. Some examples of lattice structures are shown in Figure 8.1. The first one is a randomized lattice structure. Due to the disordered lattice cells, the properties of this type of lattice structures are stochastic and difficult to control. But it can be used as implants in orthopedic surgeries. The second and the third are lattice structures with periodic unit cells. The difference is that the strut thickness of the second one is uniform, which is called homogeneous lattice structures. However, the third one has non-uniform strut thickness for specific loading conditions, which is called heterogeneous lattice structures. By properly adjusting the material in vital parts of the lattice structure, the heterogeneous periodic lattice structure can have a better mechanical performance than the homogeneous one with the same weight. Plenty of design and optimization methods [3-5] have been proposed for lattice structures to pursue better performance in different engineering applications. For example, the lattice structure is applied to achieve lightweight [3, 4], energy absorption [6], and thermal management [7]. Due to the complexity of the geometry, the fabrication of lattice structures had been the most critical issue. However, with the development of Additive Manufacturing (AM) processes, the difficulty in the fabrication was largely relieved.
Efficient Multi-Material Topology Optimization
Authors: Mirzendehdel Amir M. , Suresh Krishnan
Published: June 2021

This chapter focuses on generating optimized topologies using multiple materials. The interest in multi-material topology optimization (MMTO) stems from the well-recognized synergy between topology optimization (TO) and additive manufacturing (AM), where organic structures created through TO can be directly fabricated by a variety of AM processes. Given the rapidly increasing capabilities of AM, there is an opportunity to improve the performance of consumer products, biomedical, and aerospace components, through simultaneous optimization of topology and distribution of multiple materials.
Solid-phase epitaxial crystallization of β-Ga2O3 thin film by KrF excimer laser irradiation from backside of NiO (111)-buffered α-Al2O3 (0001) substrate at room temperature
Authors: Morita Hiroyuki , Matsushima Takumi , Nakamura Kisho , Kaneko Kenta , Kaneko Satoru , Matsuda Akifumi , Yoshimoto Mamoru
Published: June 2021

We have investigated the solid-phase epitaxial crystallization of β-Ga2O3 thin films on NiO (111) (3 nm thick)-buffered α-Al2O3 (0001) substrates prepared by pulsed KrF excimer laser irradiation onto amorphous Ga2O3 thin films from the backside of the substrate at room temperature. The results of x-ray diffraction, reflection high-energy electron diffraction, and transmission electron microscopy indicated that the solid-phase crystallization of the amorphous Ga2O3 thin film to epitaxial β-Ga2O3 film started from the film/substrate interface toward the film surface with an average growth rate of about 0.1 nm thickness per one pulse irradiation. The optical bandgap of the epitaxial β-Ga2O3 thin films (∼80 nm thick) was estimated to be 4.9 eV from the UV/Vis transmittance measurement.
Sound out the hidden colors: Photoacoustic imaging in deep tissues
Authors: Yao Junjie
Published: June 2021

Acoustically detecting the optical absorption contrast, photoacoustic imaging can overcome the penetration limit of traditional optical imaging and can provide rich functional and molecular information at large depths.
Hearables for managing auditory sensitivities using heart rate variability
Authors: Benesch Danielle , Bouserhal Rachel , Benesch Jérémie Voix
Published: June 2021

In-ear heartbeat sounds were recorded while participants were exposed to affective auditory stimuli with the aim of adapting a hearable to infer sound-induced distress.
Enhanced modal matching formulation for a cost-efficient computation of the acoustical properties of multi-layer perforated and micro-perforated partitions
Authors: Maury Cedric , Bravo Teresa
Published: June 2021

As rigidly backed micro-perforated panels (MPPs) are Helmholtz-type absorbers, their performance is typically limited to narrow frequency bands. The use of multi-layer or multi-array partitions has been widely studied to extend their absorption over a broader range. Optimal selection often requires combination of macro and micro-perforated panels constitutive of the overall partition. However, it is difficult to find a unified impedance model that may account for the whole range of hole diameters variations encountered in an optimization process. In this study, an enhanced multi-modal (EMM) formulation is developed that overcomes limitations for the domain of validity of the MPP parameters. It provides a unit cell transfer impedance that accounts for visco-thermal dissipation and high-order evanescent modes both within the perforation and at the panel walls. It can be used as a Robin-type visco-thermal boundary condition in a pure Acoustic finite element model (FEM) of a complex micro-/macro-perforated structure. This approach leads to a mixed analytical-numerical approach with a much lower computational cost than a full visco-thermal Acoustic FEM model. The inclusion of hole or panel interaction effects is then achieved through the acoustic or structural FEM parts.
Model order reduction for efficient numerical room acoustic simulations with parametrized boundaries
Authors: Sampedro Llopis Hermes , Engsig-Karup Allan P. , Pind Finnur , Jeong Cheol-Ho , Hesthaven Jan S.
Published: June 2021

This study presents a new model order reduction technique applied to room acoustic simulations using a high-order numerical scheme based on the spectral element method. The goal is to efficiently simulate iterative design processes in room acoustics, where the room acoustics with different boundary absorption properties are evaluated much quickly without solving the full wave equation. The wave-based methods are highly accurate but expensive when simulating high-frequencies and long simulation times in large and complex geometries, which are needed for industrial applications. Hence, it remains a key challenge to improve the computational performance of room acoustics simulations with different boundary material possibilities. With model order reduction, the boundary condition can be parametrized in the subsequent modelling. This allows to reduce the dimensionality of a wave-based simulator without compromising the transient wave propagation accuracy while enabling significant reductions of computational costs after initial training using proper orthogonal decomposition. We provide evidence that the combination of the high-order numerical scheme with model order reduction has significant potential value for building acoustics in terms of computational efficiency and accuracy.
Additive manufacturing of textured ceramics
Authors: Michie Matthew
Published: June 2021

The study of tailoring crystallographic gain orientation has been an area of great interest due to the ability to enhance specific material properties. Bulk textured ceramics are commonly manufactured by aligning seed grains in a polycrystalline material through tape casting. This talk will explore the idea of transitioning this technology into an additive manufacturing process. Discussing the unique challenges of 3D printing ceramic materials and obtaining proper alignment of seed gains while flowing through a nozzle. This talk will detail current efforts to model alignment of seed grains through a nozzles and create new nozzle geometry optimized for aligning particles in a ceramic slurry. This discussion will entail the current prototype materials being created and the final goal of creating textured piezoelectric material to be used in transducer applications.
Psychoacoustic phenomena in electric-guitar performance
Authors: Braasch Jonas , Braasch Joshua L. , Pastore M. Torben
Published: June 2021

Early prototypes of the electric guitar were created at about the time public address systems were invented in the 1930s, with the pure intention of making the instrument louder. However, it was not until the 1950s when artists like Link Wray, Chuck Berry, and Ike Turner used non-linear distortion as the first electronic effect to transform the electric guitar into a fundamentally new instrument. The effect adds higher harmonics and improves sustain, allowing for long notes and spectral presence. Several other effects and techniques followed (e.g., delay, chorus, flanger, phaser, tremolo, equalization, and compression), which were often used to blend the electric guitar into a band mix or to help it sonically stand out. Interestingly, the apparatus used for psychoacoustic research stems from the same electronic-circuit innovations that founded the electric guitar's electronic-effect industry. This presentation will focus on computational auditory scene analysis of variously effected guitar tracks embedded in a whole band mix to determine how these effects are used to make the guitar blend in (fusion) or stand out (transparency). To investigate this, model parameters related to loudness, masking, spaciousness, and modulation detection will be computed from audio tracks.
Drop and restoration of noise levels in Madrid during the first year of the COVID-19 pandemic
Authors: Asensio César , Pavón Ignacio , de Arcas Guillermo
Published: June 2021

From 12 March to 7 June 2020, the Madrid region experienced one of the most severe lockdowns in Europe, to contain the advance and consequences of COVID-19. The closure of schools, the cancellation of crowded events, the closure of bars and restaurants, and the regional closure, together with the strong encouragement to stay home and to telework, led to a very strong reduction of traffic levels in the city and an absence of people on the streets. As a result, noise levels in the region were dramatically reduced for a few months. After the end of the most severe phases of confinement, activity in Madrid is still recovering, and with it, noise levels are returning to pre-covid values. In this video I will show the acoustic effect of the lockdown registered by the noise monitoring networks of the city of Madrid and Madrid’s airport, and I will discuss the relationship that has been observed between acoustic and health variables in the region.
Pulsed ultrasound propagation through polydisperse contrast agent suspensions
Authors: Ovenden Nicholas , Stride Eleanor P. , O'Brien Jean-Pierre
Published: June 2021

Gas microbubbles stabilised by a surfactant or polymer coating are widely used in echocardiography and, increasingly, for quantitative studies of tissue perfusion. It is their highly nonlinear response to ultrasound excitation that makes them such effective contrast agents. It is this property also, however, that leads to image artefacts and difficulties in obtaining accurate quantitative information. There are few theoretical models describing the response of a contrast agent population that take into account both nonlinear behaviour and multiple bubble interactions. Computational complexity arises when the medium contains a polydisperse bubble population because a nonlinear ordinary differential equation (ODE) governing the bubble response must be computed for the current radius of each bubble size R0 present at each spatial location at every time step, which unfortunately makes the numerical model impractical for real-time clinical use. Further complexity occurs when near-resonant microbubbles shed their lipid coating drastically transforming the suspension’s acoustic response to subsequent pulses. In this work, we investigate approximations that can significantly reduce the computational complexity and demonstrate that, under certain parameter regimes, these approximations can simulate the nonlinear propagation of a repeated ultrasound pulses through a polydisperse contrast agent suspension to reasonably high accuracy.
A review of the effect of musical training on neural and perceptual coding of speech
Authors: Whiteford Kelly L. , Sim Angela , Oxenham Andrew J.
Published: June 2021

Several studies have reported enhanced neural coding of stimulus periodicity (frequency following response; FFR) and/or shorter neural response latencies to speech sounds in musicians than in non-musicians. Such enhanced early encoding may underlie the reported musician advantage for perceiving speech in noise. If such perceptual benefits are confirmed, it is possible that musical training may be an effective intervention for offsetting the decline of this important skill with age. This presentation will review evidence for and against the musician advantage in the neural coding and perception of speech, and will highlight several reasons to be cautious of the generalizability of the musician advantage in the published literature, including (1) small sample sizes, (2) varying definitions of musician and non-musician, (3) dichotomous between-group comparisons (e.g., comparing professional musicians to non-musicians), (4) possible speech-corpus specific effects, and (5) the multitude of degrees of freedom in FFR analyses. Efforts towards large-sample replications that use open science techniques, including preregistered hypotheses, methods and analyses, as well as open source data, should bring clarity to the association between musical expertise and the neural coding and perception of speech in noise. [Work supported by NIH under Grant R01 DC005216 and NSF-BCS under Grant 1840818.]
Tom Norris: One scientist can make a lasting difference
Authors: Kumar Anurag
Published: June 2021

Most of us in our youth have never heard of the term bioacoustics, let alone knew this could be a possible career option. Yet almost all of us in our youth have heard the fascinating sounds humpback whales make. Early on, it took an adventurous spirit, inquisitive mind, and perseverance to learn a wide variety of disciplines to study marine mammal bioacoustics. Even today, bioacoustics it typically a college course and not a full degree. Tom Norris was one of the few early scientists that helped shape what it takes to study bioacoustics and paved the way for others. With increasing concern about the potential impacts to marine mammals from noise in the ocean, there has been greater demand for those with a background in bioacoustics. Part of that overall interest has been using acoustics to passively listen and monitor marine mammal sounds, to learn more about the occurrence and distribution of these animals. Tom Norris’s efforts to create a better, more cost effective approach, helped shape the way that we use passive acoustic monitoring to study marine mammals today.
Experimental and numerical analysis of Lamb wave transmission through the coronal suture of a dry human skull
Authors: Mazzotti Matteo , Kohtanen Eetu , Erturk Alper , Ruzzene Massimo
Published: June 2021

Cranial Lamb waves have recently gained attention as potential means for ultrasound imaging and diagnostics of the skull. The inherent capability of these waves to travel for long distances across the cranial vault requires the understanding of transmission mechanisms across cranial sutures, which remain mostly unexplored. This work investigates such mechanism in the coronal suture of a dry human skull. The transmission analysis is performed experimentally by recording velocity arrays induced by short tone-bursts along curvilinear paths that intercept the suture at different locations. For each path, the experimental frequency-wavenumber spectrum of the incident wave indicates the presence of fundamental and higher order Lamb modes, with transmission being mainly associated with the fundamental antisymmetric Lamb mode. By calculating the corresponding transmission coefficients and comparing them with those obtained from a semi-analytical multilayered model of the cranial bone, we demonstrate that the coronal suture can be described by a simplified constitutive law defined by distributed shear and compressional stiffness coefficients. The experimental results and the estimated suture constitutive parameters provide the basis for a comparative analysis of the suture mechanical properties at different spatial locations, which may be employed for suture characterization and imaging.
Lessons learned teaching through a pandemic and looking forward to a post-COVID-19 classroom
Authors: Morrison Andrew C.
Published: June 2021

Many educators have faced the challenge of teaching in a world with COVID-19. Not everyone has the same amount of difficulties to work through, but each of us has the pandemic's unspoken weight affecting our daily life and work. After teaching for over a year through the pandemic, several lessons have shaped my approach to this time of emergency remote teaching. Some adaptations made to course delivery will survive in a post-COVID classroom if not entirely intact, at least with a considerable influence from the current situation. The variety of teaching modalities that have emerged have shown the possibilities of how courses can be delivered. Although there are aspects of online courses which we may never wish to repeat post-COVID, some aspects of our current situation could be useful in the future. We can continue to use remote collaboration tools when being together in a room is not an absolute necessity. We can help our students develop collaborations using these same technologies. Forming positive relationships with students and supporting how students work with their classmates has never been more important than during the pandemic. We should continue to prioritize relationship-building in a post-COVID future.
Acoustics development in China and path of collaborations with US
Authors: Zhang Likun , Wang Xiuming
Published: June 2021

This talk will start out by reviewing some of the current situations of acoustics research and education in China. There are mutual interests between the acoustical societies of both sides to maintain international communications and collaborations in acoustics research and education. Specific topics of these interests include, but not limited to, joint conferences, funding to support scholars of both sides to attend joint conferences, and acoustics journals for exchange publications. Some of these topics have been initiated and proceeded in past years. For example, the Journal of Applied Acoustics and the Chinese Journal of Acoustics published the greetings from the Editor-in-Chief of ASA journals in both Chinese and English. More work need to be done in the future. There are some existing opportunities that encourage international education and research communications. While there are so many opportunities for communications and collaborations, it can be difficult to start up. The talk will address some of these matters relating to the collaborations, including the mutual interests, existing opportunities, current status, future efforts, and potential difficulties.
Ocean acoustics research in India: Potential for collaborations
Authors: Potty Gopu R. , Ganesan Latha , Chandrayadula Tarun K.
Published: June 2021

This talk will provide an overview of the research carried out in ocean acoustics in India. The topics of special interest for international collaboration identified by some of the institutions involved in ocean acoustics research will be highlighted. The status of underwater acoustics education in India will be reviewed. Two institutions located in Chennai, India (National Institute of Ocean Technology (NIOT) and Indian Institute of Technology (IIT), Madras) are heavily involved in ocean acoustics research and their research activities will be discussed in detail. The ocean acoustics research at these two institutions has a strong field experimental component involving international collaboration. Past and ongoing research with international collaboration will be highlighted. Challenges faced by these and other institutions in fostering collaboration with international counterparts will be discussed. The scenario of ocean acoustics education and training in India will be surveyed and outlook for the future will be discussed.
Excellent acoustic development in Taiwan
Authors: Juan Shiang-I , Tsaih Lucky S.
Published: June 2021

Development of acoustics in research and field applications in Taiwan has been well established and aligned with developed countries world-wide. Taiwan has comprehensive acoustic regulations and standards for residential and hospitality building types and stringent environmental noise protection ordinances. It is the only country that has specific noise regulation for 20 Hz to 200 Hz. The Taiwan Acoustical Association (TAA) was established on 1987. Since then, thirty-two biannual meetings have been successfully held. Auditory and speech communication, building acoustics, mechanical acoustics, ultrasound, underwater acoustics, noise and vibration, as well as bio-acoustics and other related acoustic topics were covered in these meetings. According to the Taiwan Patent Search System (English version), about 187 acoustic related patents have been granted since 2004. In terms of research institutes, at least 14 top universities in Taiwan have specific major for acoustic studies. At National Taiwan University of Science and Technology, there is an architectural acoustics program under the Department of Architecture. Its team has been involved in the world-renowned performing arts center projects such as Taichung Metropolitan Opera House, Weiwuying National Kaohsiung Center for the Arts, Taipei Performing Arts Center and Taipei Pop Music Center. It can be concluded that research and field applications of acoustics in Taiwan has been valued by the people and will be continued and tuned to world-wide standards!
Ensemble average waves in random materials of any geometry
Authors: Gower Artur L. , Kristensson Gerhard
Published: June 2021

Suppose we measure the scattered field from a material with an assortment of randomly placed particles of different sizes. To get a repeatable measurement, we may need to perform the experiment many times and average over time (or space). This talk focuses on how to calculate and understand this average field. For instance, from this average field we could then calculate what effective properties, filling a homogeneous material, would lead to the same scattered field we measured. However, these effective properties are only useful if they can tell us something about the microstructure and the particles. In this talk I will show how these effective properties depend on the geometry of the material, and not just the microstructure. On the other hand, the effective wavenumbers are inherently related to only the material microstructure and not its geometry. This result comes from a framework which was deduced from first principles, using only minimal statistical assumptions. Using this framework we will also show how to calculate the average scattered field, and specialise to a sphere filled with particles. [1] A. L. Gower and G. Kristensson, “Effective waves for random three-dimensional particulate materials.” New J. Phys. (2021).
Tracking multiple humpback whales simultaneously using time-frequency representations of active intensity on DIFAR acoustic vector sensors
Authors: Thode Aaron M. , Conrad Alexander , Lammers Marc , Kim Katherine
Published: June 2021

Humpback whale song consists of sequences of frequency-modulated sounds whose exact purpose remains unknown. Tracking multiple individuals simultaneously may provide insights into song function and assist in population estimation; unfortunately, during the winter breeding season off Hawaii so many whales produce overlapping songs that identifying the same individual becomes challenging on underwater sensors spaced a few kilometers apart. Here we present a triangulation technique using three bottom-mounted DIFAR acoustic vector sensors for tracking multiple animals simultaneously. A time-frequency representation of the dominant azimuth (“azigram”) of the acoustic energy is computed from estimates of the active intensity, (i.e., the conjugate product of pressure and particle velocity). By defining a set of azimuthal sectors, azigrams from each sensor can be subdivided into a series of binary images, with each image associated with energy propagating from a particular azimuthal sector. Spectrogram correlation methods applied to binary images from different sensors yield individual song fragments that can be used to mask the original azigram, yielding the azimuth of the fragment from each sensor, and thus the singer’s position. The technique, which has also been demonstrated on coral reef fish, is illustrated using singer data collected in 2020 off Maui, Hawaii.
Atlantic deepwater ecosystem observatory network: Patterns of acoustic backscatter and community structure of the U.S. Outer Continental Shelf
Authors: Miksis-Olds Jennifer , Warren Joseph , Blair Hannah , Lucca Brandyn M.
Published: June 2021

Three nodes in the Atlantic Deepwater Ecosystem Observatory Network (ADEON) network on the U.S. Mid- and South Atlantic Outer Continental Shelf (OCS) contain an upward looking, multi-frequency echosounder system. Data was collected from November 2017–December 2020 at these sites extending from the OCS waters of Virginia down to Florida. Along shelf backscatter comparisons were made for general scattering groups related to fish and zooplankton across time and latitude. Unique seasonal patterns were observed across sites both in terms of volume backscatter magnitude and community structure. Measurements made within this research program will serve as a baseline for pattern and trend analyses of acoustic backscatter related to ecosystem components of this traditionally under sampled, offshore region. Study concept, oversight, and funding were provided by BOEM under Contract No. M16PC00003, in partnership with ONR and NOAA. Funding for ship time was provided under separate contracts by ONR, Code 32.
Basis function choice for trans-dimensional models in geophysical inference
Authors: Dettmer Jan , Ghalenoei Emad
Published: June 2021

Inference methods depend on parametrization choices. Over-parametrized, under-parametrized, and trans-dimensional (trans-D) models are routinely chosen. Over-parametrization employs space discretization below the resolution power of the data and includes regularization (e.g. Tikhonov) to control the amount of model structure. Under-parametrized models employ fewer parameters, and practitioners choose model complexity (e.g. the number of seabed layers) that is consistent with data information, often based on incomplete prior information. Trans-D models assign model complexity based on data information in an automated, data-driven procedure. The success of trans-D models depends on the choice of basis function for space partitioning. We review existing trans-D approaches and present new ones for 2D and 3D Earth models. Existing approaches include Voronoi partitioning, wavelet decomposition, and polynomial shapes, which can produce inadequate results. New approaches use various degrees of prior information when assigning the basis. The approaches include multiple nested Voronoi diagrams, a combination of grid data and alpha shapes, and partitioning of Voronoi diagrams with horizontal and vertical lines and planes. Since the computational burden is significant for 2D and 3D Earth models, we study various algorithms to carry out partitioning and show that approximate nearest neighbours are sufficiently accurate and outperform other methods.
Quiet oceans: United States Virgin Islands coral reef soundscapes in the age of coronavirus
Authors: Clark Hadley G. , Aoki Nadège
Published: June 2021

The COVID-19 pandemic has led to unprecedented changes in human behavior around the world. These changes have impacted local soundscapes in both terrestrial and marine environments resulting in a global ‘quieting’ event that has allowed for the opportunity to evaluate the activity of soniferous organisms in unique acoustic environments. Across the world’s oceans, patterns of commercial, research, and recreational vessel traffic have all been altered, with corresponding alterations in the anthropogenic contribution to underwater noise. To assess these changes we used long-term acoustic recorders at three different coral reef sites on the Southern coast of the island of St. John in the United States Virgin Islands (USVI). We compared conditions pre-coronavirus outbreak (2019) and post-outbreak (2020) and found a decrease in the incidence of boat noise over the course of the pandemic. Because anthropogenic noise tends to overlap with the low frequencies used by marine fishes and invertebrates for sound production and detection, we predicted that changes in boat noise patterns would lead to concurrent changes in biological sound production of coral reef organisms. Understanding the impacts of this “quiet time” on marine organismal activity in the USVI could play a role in worldwide coral reef acoustic studies and conservation efforts.
Long term very low frequency ambient noise: A window to the ocean and atmosphere
Authors: Eller Anthony I. , Heaney Kevin D. , Murray James J. , Bradley David L.
Published: June 2021

Long term time series data of ambient noise in deep water from a site near Wake Island in the western Pacific provide a window into processes occurring in the ocean and in the atmosphere. Acoustic noise data in the Very Low and Ultra Low Frequency bands show strong frequency components at major tidal frequencies, are correlated with El Niño Sea Surface Temperature Anomaly time records, and correlate also with yearly wind fluctuations. Directional ambient noise data also allow tracking of distant storms. Noise at 1 Hz was chosen in particular for study because the noise sources are primarily environmental and, thus, the data may serve as a harbinger of pending environmental change.
An innovative MEMs peizo speaker
Authors: Klasco Mike , Ricci Michael , Shaw Neil A.
Published: June 2021

MEMs micro-speaker development has trailed behind MEMs microphone development by over two decades due to fabrication and acoustical challenges. While MEMs microphones only need to respond to minuscule displacement, generating sound energy requires both motor force and far higher volume velocity of the transducer mechanism. Recent development of a full bandwidth piezo-MEMs micro-speaker with a silicon diaphragm creates a rigid, light, fast responding transducer with high resistance to humidity and low thermal expansion. Fabricated using a monolithic MEMS semiconductor process eliminates calibration and driver matching. 20 Hz to 20kHz frequency response is delivered in occluded earbud, IEM, and hearing aid applications. The 20 kHz resonance peak provides a smoothly increasing response in the upper octaves. This extra amplitude allows for a significant increase in hearing aid gain and bandwidth over balanced armature transducers. The device is packaged in both top- and side-fire port configurations with earbud EVKs currently shipping. Integration of the amp, on the package substrate or SiP module, opens possibilities for more compact devices, longer battery life, lower cost, and more robust construction. The combination of audio fidelity, size, and speaker to speaker uniformity is not possible with traditional voice coil or hybrid MEMS approaches.
FCS technology: A novel electrodynamic transducer architecture
Authors: Vedier Paul
Published: June 2021

For a century now, acoustic electrodynamic transducers have been bound by axisymmetric motor structures for high performance due to the assumption in transducer theory that the diaphragm moves pistonically for all operating frequencies. This is of course a flawed assumption, and results in much research and development being focused on the vibro-acoustic components of the driver to minimize cone breakup at higher frequencies.A new architecture for the electrodynamic motor has been developed which helps to address this inherent problem. Flat Core Speaker (FCS) technology presents an architecture that is a rearrangement of the conventional electrodynamic motor structure with a planar voice coil and bobbin assembly that is situated between two parallel bar magnets. This results in a high aspect ratio design where the bobbin runs along the length of a flat diaphragm, leading to even force distribution, and therefore pistonic movement, while utilizing a thin profile with a flat diaphragm. COMSOL simulations and Klippel measurement data support these claims and show evidence of FCS technology having comparable performance to conventional drivers in a slimmer profile and blowing conventional high aspect ratio driver performance out of the water.
Laser-based comparison calibration of laboratory standard microphones
Authors: Wagner Randall , Allen Richard A. , Dong Qian
Published: June 2021

Laboratory standard microphones, which have characteristics that are specified in international and U.S. national standards, are condenser microphones used for highly accurate sound pressure measurements and calibrations. A precision laser-based comparison calibration method for these microphones is described. This method uses laboratory standard microphones calibrated by the pressure reciprocity method as transfer standards, or reference microphones, to calibrate other laboratory standard microphones, or test microphones. Electrical drive current and microphone diaphragm velocity are measured while the microphones are driven as transmitters/sources of sound; the microphone diaphragm velocity is measured using scanning laser-Doppler vibrometry. The reference and test microphones are measured consecutively. Sensitivities determined using this method display very good agreement with those determined directly by the pressure reciprocity method for seven such test microphones at 250 Hz and 1000 Hz. At these frequencies of calibration, the expanded (coverage factor, k = 2) uncertainties of this comparison calibration method for these microphones are ±0.05 dB at both frequencies. These expanded uncertainties compare favorably to those of the reciprocity-based comparison calibration service done with a large-volume acoustic coupler at the National Institute of Standards and Technology, which are ±0.08 dB at 250 Hz and 1000 Hz.
Constant pressure decibel (A weighted) and decibel (C weighted) frequency response of microphones and the expanded uncertainties involved therein
Authors: Godase Aruna , Surve Farhat
Published: June 2021

In practice, a microphone is calibrated in a closed coupler, wherein sound pressure is distributed uniformly over the diaphragm. Nonetheless, in that case, the problem of sound reflection remains indispensable. A technique that overcomes this limitation and augments the coupler calibration method is offered. Also, the frequency response data provided by the manufacturer is always A-weighted. The A and C-weighted frequency response characteristics of a variety of microphones is studied using the testing and calibration suite in the direct field of the source which overcomes the problem of sound reflection. The frequency response in the 100 Hz to 16 kHz frequency range has been examined at constant SPL of 82 dB. The implementation and reliability of the technique is evaluated by examining the expanded uncertainties involved therein. Furthermore, the A-weighted and C-weighted constant pressure frequency response in case of each microphone is compared. A detailed description of the procedure is presented, along with assessments, wherein the reliability of the results is evaluated over Type-A and Type-B uncertainties.
Directional factors of radially polarized piezoceramic cylindrical transducers
Authors: St. Pierre Michael , Brown David A. , Bachand Corey L.
Published: June 2021

An experimental investigation on the directional factors of radially polarized piezoceramic cylindrical transducers as a function of aspect ratio and for different design boundary conditions (fluid-filled, air-backed, and open-closed squirter) is presented. Several prototypes were tested for their acoustic properties (impedance, transmit sensitivity, and directional factor). For the free-flooded designs, the directional factor radiation transitions from mainly axial to mainly radially (side walls) for increasing height-to-diameter. Also, a model of directional factor is presented using a coaxial array of toroids for the free-flooded transducer prototypes. [Research supported in part by ONR and the Marine and UnderSea Technology Research Program (MUST) at UMass Dartmouth.]
Effects of stress on properties of soft piezoelectric and single crystal elements under typical operational depth
Authors: Aikins Eric K. , Brown David A. , Bachand Corey L.
Published: June 2021

Electromechanical properties (coupling coefficient, dielectric constant, elastic compliance and piezoelectric constant) of piezoelectric ceramics are affected by exposure to compressive stress. This investigation explores the extent of changes in properties of spherical and tangentially polarized cylindrical transducers made of soft PZT-5 when exposed to pressure up to 1500 psi (equivalent to 1000 m) of water depth. Also, the pressure effect on Fully Active (FA) single crystal cylindrical transducer exposed to circumferential stress up to 380 psi (250 m depth) was investigated. In the spherical PZT-5, the planar coupling coefficient decreased by 15%, dielectric constant decreased by 40%, piezoelectric constant decreased by 35% and the elastic compliance decreased by about 10%. The single crystal transducer’s effective coupling coefficient k32eff increased by8%, dielectric constant by 90%, elastic compliance by 40% and the effective piezoelectric constant d32eff by 75%. For the tangentially polarized cylindrical transducer, the sensitivity of dielectric constant and piezoelectric modulus to the compressive stress is shown to be less than radially polarized case. The setup of the experiment ensured the elimination of external effect due to loading on the transducers.
Vibro-acoustics of Central Africa harps
Authors: Fabre François B. , Le Carrou Jean-Loic , Chomette Baptiste
Published: June 2021

Central Africa harps are string instruments, often anthropomorphic, whose soundbox is built from a hollowed out tree trunk. There strings, usually 8 in number using nowadays fishing line, are wrapped to wooden tuning pegs on the neck and attached to a tailpiece placed under animal skin used as soundboard. Each instrument-making element can vary according to ethnic groups and material availability. This study aims at understanding the vibro-acoustic behavior of these instruments in order to determine relevant acoustic descriptors linked to there building process. Hence, a numerical model is developed based on the Udwadia-Kalaba modal formulation, relying on substructuring concepts. Each subsystem's dynamics is described by its modal parameters in terms of unconstrained modes and the coupling is enforced by boundary conditions. Strings displacement is described in two polarizations including geometrical nonlinear effects. Modal parameters are experimentally identified, on severa harps collected from different ethnic groups, and turn out to be discriminating descriptors. The reliability of the model is validated against laboratory measurements. Finally, sound syntheses based on the proposed approach are compared to experimental data, showing good agreement. [This work, part of the project NGombi, was funded by the Agence Nationale de la Recherche (French National research agency), Grant No. ANR-19-CE27-0013-01.]
Inter-mode patterns in bundengan string vibrations
Authors: Parikesit Gea O.
Published: June 2021

The bundengan, a folk zither instrument from Indonesia, has a unique timbre because its strings are added with small bamboo clips. The non-homogeneous mass distributions allow the strings to imitate the sound of metal percussions in the gamelan ensemble. Moreover, the clever design of the bamboo clips allow the bundengan timbre to be controlled easily by sliding the clips along the strings. Using computer simulations, we have systematically varied both the position and the mass of the bamboo clips, resulting in a rich catalogue of vibration spectra. In these spectra, we have observed peculiar patterns in the graphs of vibration-frequency -vs- clip-position; see https://www.youtube.com/watch?v = 8kacFhICXs and https://www.youtube. com/watch?v = 1UdwGANtSAU for the shapes of the patterns. These patterns, which occur across different vibration modes, evolve as the mass of the bamboo clips are increased. In the extreme case where the bamboo clips are very heavy, these patterns can be explained by a modified version of the Mersenne’s Law.
Conformations of ring polymers with excluded volume interactions
Authors: Handa Manisha , Biswas Parbati
Published: June 2021

The influence of distance dependent excluded volume interactions (EVIs) on the conformational properties of ring polymers is investigated within the principles of Rouse–Zimm theory. This study characterizes the structural features, i.e., the mean square radius of gyration, static structure factor, scattering intensity, fractal dimensions, and the mean square intermonomer distances of ring polymers in dilute solutions. The excluded volume interactions between the nonbonded monomers are modeled by a harmonic potential, where the strength of these interactions is evaluated from Flory’s mean-field approach. The mean square radius of gyration of the rings with EVI follows a similar scaling relation as its linear analog with the degree of polymerization. Unlike linear polymers, the maximum in the Kratky plot of the static structure factor is observed as a result of an increased segment density due to the circularity constraint. EVI marks a structural transition from relatively compact conformation for the smaller rings to expanded conformations for larger ones. The fractal dimension of the rings with EVI lies between those of the random walk and the self-avoiding walk models of linear polymers in three dimensions. This theoretical model produces a relatively pronounced effect of EVI for larger rings. An understanding of the influence of EVI on conformations of the ring polymers at a single molecule level may be applied to various naturally existing cyclic biomolecules such as plasmids, cyclic proteins, and polysaccharides.
Mexican funding agency forces out early-career researchers
Authors: Ortega Rodrigo Pérez , Jaber Inés Gutiérrez
Published: June 2021

Conacyt faces at least 145 wrongful termination lawsuits.