bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of individual differences of vibration duration of tuning forks
Authors: Nomizu Kyota , Otsuka Sho , Nakagawa Seiji
Published: June 2021

Tuning forks are used in the fields of music, clinical tests of vibrotactile sensation/audition, and healing. For the tuning fork, longer duration of the fundamental tone is required as well as accuracy of the frequency of the fundamental tone. Additionally, it is desirable that the harmonic tone decreased immediately after the stroke. However, in the manufacturing process of the tuning forks, only the fundamental frequency is tuned and durations of tones have not been evaluated. In this study, we evaluated the effective durations of fundamental and harmonic tones generated from several kinds of tuning forks in order to clarify the parameters that affect them. Measurements of sounds generated from individual tuning forks were repeated with several holding pressures and individual differences among tuning forks and effect of the holding pressure were examined. As results, significant individual differences in the effective duration of fundamental and harmonic tones were observed. In addition, the durations of the fundamental and harmonic tones varied with change of the holding pressure, however, the holding pressures showing the longest duration were different between the fundamental and harmonic tones and also different among individual tuning forks.
The implementation of a soundscape approach and methodologies in an acoustic consulting context
Authors: Allen Mitchell , Caulkins Terence , Smith Brendan , Patel Raj
Published: June 2021

Acoustic engineering practice in the built environment increasingly aims to implement a soundscape approach as a base offering rather than supplementary to traditional noise control engineering. With the recent introduction of parts 1, 2, and 3 of ISO 12913, a suite of new resources has become available to apply a soundscape design approach within the built environment. There are various opportunities and obstacles associated with implementing the theory and standards as a built environment consultancy for clients on real world projects. This presentation discusses some examples and approaches adopted by Arup across the globe and highlights successes and barriers experienced along the way. Specific Arup project case studies of different scales are included where a shift towards adopting a soundscape design approach has been utilized in the broadest sense. Additionally, the role of acoustic consultants as a connection between theory, standards, and implementation is discussed.
Introduction and application of a proposed method for quantitative soundscape analysis: The soundscape code
Authors: Wilford Dylan , Miksis-Olds Jennifer , Martin Bruce , Lowell Kim
Published: June 2021

A novel methodology for the analysis of soundscapes was developed in an attempt to facilitate quick and accurate soundscape comparisons across time and space. The methodology, proposed here for the first time, consists of a collection of traditional soundscape metrics, statistical measures, and acoustic indices that were selected to quantify several salient properties of marine soundscapes: amplitude, impulsiveness, periodicity, and uniformity. The metrics were calculated over approximately 30 h of semi-continuous passive acoustic data gathered in seven unique acoustic environments. The resultant metric values were analyzed and cross-examined to determine which combination most effectively captured the characteristics of the respective soundscapes. The best measures of amplitude, impulsiveness, periodicity, and uniformity were combined to form the proposed “Soundscape Code,” which allows for rapid multidimensional and direct comparisons of salient soundscape properties across time and space. The soundscape code methodology was then applied at three deep-sea habitats located in the Mid- South Atlantic Outer Continental Shelf (OCS) region that varied in depth, substrate, proximity to shore, and community structure. Soundscape code metrics highlighted nuanced differences in the acoustic environments and allowed for rapid, direct, quantitative comparisons to be made between the sites.
Development of analytical models for calculating the characteristics of intense acoustic waves propagating in a stratified atmosphere
Authors: Gusev Vladimir A. , Zharkov Denis A.
Published: June 2021

The time profiles and characteristics of sonic boom waves during propagation in a density-stratified atmosphere are calculated. It is shown that this stratification leads to a significant change in wave parameters: the wave amplitude, the characteristic distances at which the wave transformation is manifested, the width of the shock front. It is shown that the effective role of viscosity decreases when the shock wave propagates down to the earth's surface. So the width of the shock front decreases. Two methods are being developed for analytical calculation. The first one, the nonlinear geometric acoustics approximation, allows obtaining the Burgers equation with a variable viscosity to describe the wave field along the ray. Some exact solutions and asymptotic solution for low viscosity are obtained. This method is not applicable in focusing regions. The second method is based on the application of a modular nonlinearity model. Replacing the quadratic nonlinearity with a modular one allows obtaining a system of linear equations, the solution of which is possible. The difficulty lies in the correct construction of the discontinuity in the profile and subsequent stitching of solutions for different polarities. [This study was supported by the Russian Foundation for Basic Research (Project No. 20-02-00493-a).]
Sonic boom simulation for boom carpet determination
Authors: Jäschke Jacob J. , Liebhardt Bernd
Published: June 2021

The Institute of Air Transportation Systems in Hamburg, Germany, researches methodologies for optimized supersonic flight routing that prevents the (primary) sonic boom from reaching the ground. The sonic boom shall either be cut off vertically or laterally. In initial trials, lateral cutoff positions of the sonic boom carpet were searched geometrically by ray tracing. Thereby, it was found that smooth interpolation of atmospheric data is necessary for geometrical convergence of different ray tracing methods, and that determining the marginal ray was oftentimes virtually impossible leeward. (These findings will be elaborated in more detail.) For those reasons, acoustic propagation has been introduced based on the Augmented Burgers equation, and implementing the Tricomi equation for covering flight maneuvers is planned in the short term. Our main research goal is finding numerical methods for determining the acoustic sonic boom cutoff that are first and foremost practical, i.e., fast, accurate, and robust. In this respect, we will discuss different termination conditions in signature propagation for the purpose of sonic boom carpet computation.
Sonic boom reflection over irregular terrain
Authors: Emmanuelli Ariane , Dragna Didier , Ollivier Sebastien , Blanc-Benon Philippe
Published: June 2021

An overview of recent studies on sonic boom reflection over irregular terrain is presented. Numerical simulations based on the two-dimensional Euler equations are performed using high-order finite-difference time-domain techniques, allowing for an accurate prediction of diffraction. Studies are done for two sonic boom waves: a conventional N-wave and a low-boom wave. First, ground elevation effects on sonic boom are examined. An academic ground profile, corresponding to a terrain depression, is considered to highlight mechanisms at play. In particular, caustics due to ground elevation variations induce another contribution at the ground level, in the form of a U-wave. Results for real ground profiles are then presented and cumulative effects, due to the succession of terrain irregularities, are shown. Second, propagation of sonic boom over an urban profile is investigated. Possible resonance effects inside street canyons are discussed. For all cases, statistics of noise metrics are examined. [This work was performed within the framework of the LabexCeLyA of the University of Lyon, within the program ‘‘Investissements d’Avenir” (ANR-10-LABX-0060/ANR-16-IDEX-0005) operated by the French National Research Agency and has received funding from the European Union's Horizon 2020 research and innovation programme (Grant Agreement No. 769896 (RUMBLE).]
Cues to monaural edge pitch in single auditory nerve fibers
Authors: Li Yi-Hsuan , Joris Philip X.
Published: June 2021

The spectral edge of a bandlimited noise can create a pitch sensation, called “edge pitch,” which is slightly mismatched to the edge frequency. This pitch is usually speculated to reflect neural lateral inhibition but could also reflect temporal cues. We looked for such cues recording responses of single auditory nerve fibers in the anesthetized chinchilla to edge pitch stimuli. For every stimulus, we compute shuffled autocorrelograms for all recorded fibers and pool them in a population interval distribution (PID) from which we obtain the most common interval. We also quantify the slower “envelope” fluctuations in firing resulting from cochlear bandpass filtering of the bandlimited noise stimulus. Single fibers shows systematic temporal changes related to the spectral edge of the stimulus when it does not cover the fiber's frequency filter. Across the population of fibers, the estimated pitch based on the dominant interspike interval shows trends that are similar, qualitatively and quantitatively, to those observed behaviorally. Slower envelope fluctuations also systematically vary with the relationship of edge frequency to fiber CF, and are another potential temporal cue to the presence of the edge frequency. We conclude that temporal cues to edge-pitch are present in the auditory nerve at multiple time scales.
Controlled cortical impact-induced brain injury alters auditory sensitivity in laboratory mice
Authors: Burke Kali , Alexandris Athanasios S. , Koliatsos Vassilis , Lauer Amanda M.
Published: June 2021

Individuals who have sustained a traumatic brain injury (TBI) often report auditory dysfunction including changes to their hearing sensitivity, tinnitus, and hyperacusis. One factor that may have a significant contribution to a person’s post-injury outcomes is whether the TBI occurred in combination with a high intensity noise exposure (e.g., as in the case of a car accident). To date, no study has examined the combined effects of a brain injury and high intensity noise exposure to evaluate whether this would lead to worse overall auditory outcomes than either trauma in isolation. In this study we tested the auditory sensitivity of male and female CBA/CaJ laboratory mice before and 3, 7, 14, 30, 60, and 90 days after acoustic (noise exposure), physical (controlled cortical impact), and combined acoustic and physical injuries. Following completion of the experiment, cochlear and brain tissue was fixed with paraformaldehyde and central and peripheral auditory structures were examined for damage. Our preliminary results show that physical injuries alone cause damage to the auditory sensitivity of mice measured using the auditory brainstem response, reduced acoustic startle responses in quiet and noise, yet hair cells remain intact. Long-term consequences on auditory perception are being tracked in these mice.
Grasshopper mice alter vocalizations with age-related and noise-induced hearing loss
Authors: Kobrina Anastasiya , Hidau Mahendra , Riede Tobias , Guthrie O’Neil , Pasch Bret
Published: June 2021

Age-related and noise-induced hearing loss disorders are among the most common pathologies affecting Americans across their lifespans. Loss of auditory feedback due to hearing disorders is correlated with changes in voice and speech-motor control in humans. Although rodents are increasingly used to model human age- and noise-induced hearing pathologies, few studies have assessed vocal changes that co-occur with hearing deterioration. Northern grasshopper mice represent a candidate model because their hearing sensitivity is matched to the frequencies of long-distance vocalizations that are produced using vocal fold vibrations similar to human speech. In this study, we quantified changes in auditory brainstem responses and vocalizations related to aging and noise-induced acoustic trauma. Mice showed a progressive decrease in hearing sensitivity for pure tone stimuli, with males losing hearing more rapidly than females. Mice experienced severe hearing loss across all frequencies after exposure to noise. Frequency and duration of long-distance vocalizations were affected by hearing loss similar to findings in other mammals. Our findings indicate that grasshopper mice experience age- and noise- induced hearing loss and concomitant changes in vocal output, making them a promising model for hearing and communication disorders.
Transformable topological mechanical metamaterials based on Maxwell lattices
Authors: Mao Xiaoming
Published: June 2021

Maxwell lattices are mechanical networks on the verge of instability and feature convenient mechanisms of transformation. They exhibit topologically protected floppy modes and states of self-stress, offering an excellent platform for topologically robust and yet transformable mechanical and acoustic properties. In this talk, we will discuss recent progress in developing topological mechanical metamaterials based on Maxwell lattices, from dramatic changes of surface stiffness upon a small stimuli, to programmable stress distribution for fracturing protection, and nonreciprocal propagation for nonlinear waves. These results reveal great potential for Maxwell lattices as a new class of topological mechanical metamaterials with emerging applications.
Collecting experimental data online: How to maintain data quality when you can’t see your participants
Authors: Rodd Jennifer
Published: June 2021

Researchers are often nervous about collecting experimental data online because unlike lab-based experiments they cannot directly control their participants’ hardware, software or their location. They also cannot directly observe participants’ behaviour during the experiment. I will review the key issues that arise from using remote participants, and suggest a systematic approach to (i) participant recruitment, (ii) data collection and (iii) data analysis that ensures high levels of data quality. I will argue that it is inevitable that online recruitment will lead to the collection of unsuitable data, and that while we should do all we can to improve the quality of our collected data, it is perhaps more important to focus on ensuring that poor quality data is not included in our final analyses. A cornerstone of this approach is the careful pre-registration of exclusion criteria based on task piloting. I will also suggest that this principled approach to data quality control is often missing in lab-based settings and that the lessons learned due to running experiments online can be broadly applied to a range of experimental paradigms.
Testing performance in complex listening tasks with primary school children in remote settings
Authors: Visentin Chiara , Pellegatti Matteo , Prodi Nicola
Published: June 2021

When assessing the impact of the classroom sound environment on students’ learning an approach as much ecological as possible is needed. Tasks should be presented collectively to the entire class in real-life scenarios, as during regular school-day activities, thus preserving self- and mutual perception of the students. However, in this specific era of pandemic, such an ecological approach cannot be pursued and new ways for testing students are necessary. In this study, the method used to present two experiments remotely to primary school children (8 to 10 year olds) is described. Online platforms with specific design tools and touch-screen devices were used to build and administer the tasks. Auditory stimuli were presented via headphones, whose effect was compensated by filtering. In the sound stimuli the typical reverberant environment of the classroom was simulated by auralization. Aiming to improve as much as possible the face validity of the experiments, the tests were presented collectively to the students in their classrooms even though each children performed the task individually and at his/her own pace. Moreover, the tasks were presented and explained by the experimenters by using interactive whiteboards, as during distance learning.
Running voice identity perception studies online
Authors: Lavan Nadine
Published: June 2021

In this presentation, I will give a broad overview of my experience running voice identity perception studies online. I will give examples of the kinds of perceptual studies I have run online using testing platforms, such as Qualtrics and Gorilla, paired with the online recruitment service Prolific. As part of this overview, I will discuss some ways to ensure and improve data quality, such as adding vigilance trials, limiting the duration of the online experiments, and including other checks that enable researchers to assess whether a participant's data is useable. Finally, I will highlight some of the advantages and considerations that are specific to online testing. For example, it is possible to test hundreds of participants in one afternoon using online testing, thus dramatically speeding up data collection. However, it is very difficult to tightly control the participant's listening environment and the use of hardware (e.g., type of speakers or headphones used).
Bayesian signal processing: A practical guide to particle filtering design and performance
Authors: Candy James V.
Published: June 2021

When uncertain acoustic processes can no longer be characterized by Gaussian or for that matter unimodal (single peak) distributions along with the fact that the underlying phenomenology is nonstationary (time-varying) and nonlinear, then more general Bayesian processors must be applied to solve the underlying signal enhancement/extraction problem. A particle filter provides a solution to this multimodal (multiple peaks) posterior distribution estimation problem in noisy acoustic environments. A particle filter is a sequential Markov chain Monte Carlo processor capable of providing reasonable performance for data evolving from a multimodal distribution by estimating a nonparametric representation of the posterior distribution from which a multitude of meaningful statistics can be retrieved. However, the question of evaluating its performance can be challenging even for the simplest of processes. For instance, it is well-known that Kalman filter optimality can be obtained only when the resulting error residuals (innovations) are zero-mean and white. It is not that simple for the particle filter. Once characterized, the performance of the particle filter must be analyzed for it to be of practical value. Here a set of design and analysis criteria is discussed and applied to demonstrate their ability to quantify particle filtering performance.
Uncertainty and interdependence of localization parameters within Bayesian framework for near-field source localization
Authors: Metzger Thomas , Xiang Ning
Published: June 2021

Localization of sound sources relative to a receiver is of great interest in many acoustical applications. In a recent study, a Bayesian framework was presented for the three-dimensional localization of an unknown number of sound sources within the near field of a spherical microphone array. Within this model-based probabilistic framework, the spherical beamforming model is formulated to include dependence on radial distances of potentially multiple sources in the near field. The focus of this work is threefold. First, to analyze the uncertainty and error of the localization results. The results provide estimates of the source distance(s) with increasing uncertainty at increased distances. Second, to analyze the interdependence of source distance and amplitude on the estimation results when multiple sources are present. Finally, this work discusses how mitigation of this interdependence affects the uncertainty and error for multiple sound sources.
Spatio-temporal Gaussian process regression for room impulse response interpolation with acoustically informed priors
Authors: Caviedes-Nozal Diego , Fernandez-Grande Efren
Published: June 2021

The reconstruction of sound fields in a room from a limited set of measurements is a central problem in acoustics, with relevant applications in e.g. acoustic analysis, audio, or sound field control. Conventional approaches rely on measuring the room impulse response (RIR) at several locations in the room, and fitting a wave model that enables to estimate the field at other locations—via solving an inverse problem. Previous studies have shown that the reconstruction of RIRs strongly depends on the regularization method used to solve the problem, and that enforcing sparsity is beneficial for the reconstruction of the early part of the RIR. This work studies Gaussian processes with time-dependent regularization in order to exploit the temporal properties of RIRs. The inverse problem is solved in the time domain, where hierarchical Bayes is applied in order to explicitly promote solutions where waves are more likely to propagate as time evolves. The model aims at reconstructing both the early part, and the late part of the RIRs. The performance of the proposed model is studied with experimental measurements, and compared to classical reconstruction methods with l1 and l2-norm regularization schemes
COVID-19 impact on the Northern Gulf of Mexico soundscapes
Authors: Sidorovskaia Natalia , Mathew Naomi
Published: June 2021

Changes in the Gulf of Mexico soundscapes due to COVID-19 are investigated. Baseline ambient noise recordings from five Environmental Acoustic Recording System buoys in the Mississippi Valley/Canyon region between May 2018 and June 2020, collected as a part of the collaborative efforts funded by BOEM, are analyzed. The statistical data processing is based on the standards developed for the previous large-scale ocean ambient noise monitoring projects; extracted acoustic metrics are directly comparable to the levels reported in the Baltic Sea, the North Atlantic, and the North Sea . The monthly medians of 1/3-octave band Sound Pressure Levels (SPLs) vary up to 15 dB re 1 μPa across sites depending on surrounding anthropogenic activities and local propagation conditions that makes it challenging to recognize the variations due to the pandemic. Overall, the deepest site appears to have the highest SPLs at the low frequency bands and the lowest SPLs at the mid-frequency bands. The mid-frequency band highest SPLs are observed at the shallow site and the site outside the canyon. Exploration surveys and industrial activities were present across all COVID-19 impacted months. More subtle changes in ambient levels due to the pandemic impact will be discussed in the presentation.
Global shipping soundscapes: A study of the COVID-19 impact
Authors: Verlinden Chris , Heaney Kevin D. , Rosenthal Sarah , Murray James J.
Published: June 2021

The global ocean soundscape, at frequencies below 400 Hz, is dominated by shipping and at some select frequencies marine mammals and large storms. In this paper, we present a global model of the shipping and wind noise soundscape. The Parabolic Equation (PE) Model is used to compute the propagation loss from a grid of points through the dynamical ocean to a high resolution grid of receivers. Source depths of 5 m are used for ships and 1/4 wavelength are used surface wind. The combined wind/shipping soundscape can then be generated using satellite observations of the shipping positions via Automated Identification Services and the wind speed at 10 m. Both databases were provided by SPIRE Inc. SPIRE provided the shipping AIS for March/April 2018 and March/April 2020. The global shipping soundscape for these two time periods reveals a drop of 3-6 dB depending upon position at 50 Hz from the reduction in surface shipping traffic due to the COVID-19 global shut down.
Sound field fluctuations in shallow water waveguide in the presence of nonlinear internal waves and estimation of their speed. ASIAEX experiment as a case study
Authors: Katsnelson Boris , Grigorev Valery , Jiang Yanyu
Published: June 2021

Spectra of the sound field fluctuations in shallow water waveguide in the presence of nonlinear internal waves (NIW) are studied and used for solution of inverse problem: to estimate variability of speed of NIW using results of ASIAEX experiment. ASIAEX was carried out in the South China sea since April 29 until May 14, 2001, a few tens of solitary NIW with amplitude up to 100 m were registered, moving toward the beach. Sound pulses (M-sequences, frequency 224 Hz) from the source were propagating in narrowing channel (350 m–120 m, distance 30 km) toward the beach in the presence of NIW. It was shown earlier by authors that spectrum of fluctuations measured during NIW’s motion contains peaks at frequencies F depending on speed v of NIW and scales of interference beating D of waveguide modes F ∼ v/D. D depends on bathymetry and sound speed profile in a waveguide. Using measurement of peak frequencies and known values of D, and using matching procedure between modeling and experimental data, variations of v were found for set of above mentioned events of NIW passing. Results were compared with direct measurements using satellite observations. [Work was supported by RFBR under Grant No. 20-55-S52005.]
Long-term analysis of ocean noise floor in the northeast Pacific Ocean
Authors: Schwock Felix , Abadi Shima
Published: June 2021

Characterizing the ocean noise floor is important for tracking long-term acoustic changes and creating environmental regulations to mitigate the effects of human activities on the ocean soundscape. Underwater noise levels have been measured at two sites in the northeast Pacific off the coast of Oregon between 2015 and 2019. The acoustic data were recorded continuously at a sample rate of 64 kHz at 81 m depth and 581 m depth at the continental shelf and slope, respectively. Sequential one-minute power spectral density estimates are computed and used to calculate spectral probability density functions (SPDFs) for every month of the measurement period. The ocean noise floor is then defined as the 5th percentile of the SPDF. Multi-year data are used to compute time series of the ocean noise floor at various frequencies, which are then examined for long-term trends and seasonal patterns. The frequency dependence of the noise floor is analyzed and the results are compared between two measurement sites. Environmental data from surface buoys and Conductivity, Temperature, Depth (CTD) instruments collocated with the hydrophones are used to study how the ocean noise floor changes with wind, temperature, and sound speed. [Work supported by ONR.]
Seasonal variations of ambient sound and ice draft in the Northwest Passage between 2018 and 2021
Authors: Cook Emmanuelle , Barclay David R. , Richards Clark , Nudds Shannon
Published: June 2021

The Barrow Straight Real-time Observatory is a cabled underwater monitoring station operated by Fisheries and Oceans Canada in the Tallurutiup Imanga National Marine Conservation Area. The observatory measures temperature, salinity, pressure, dissolved oxygen, currents, ambient noise and ice draft. Every 2 h a hydrophone records a 1-min pressure time series and generates a spectrogram with a frequency range of 10–6390 Hz and time resolution of 1 s. The IPS generates a histogram of ice draft measurements every 2 h. Data are sent in near real-time to the Bedford Institute of Oceanography via satellite. The average monthly sound levels follow seasonal ice variations with higher frequencies varying more strongly with season than the lower frequencies and depend on the timing of ice melt and freeze-up. Ambient levels are higher in the summer during open water and quieter in the winter during periods of pack ice and shore fast ice. An autocorrelation of weekly noise levels over the ice freeze-up and complete cover periods reveal a ∼24 h periodic trend in noise at high frequencies (>1000 Hz) which is caused by tidally driven surface currents in combination with increased ice block collisions or increased stress in the shore fast sea ice.
Assimilation of acoustic thermometry data in Fram Strait
Authors: Geyer Florian , Gopalakrishnan Ganesh , Sagen Hanne , Cornuelle Bruce , Mazloff Matthew M.
Published: June 2021

The 2010i–2012 ACOBAR acoustic thermometry experiment in Fram Strait resulted in 2-year-long timeseries of sound speed and temperature. These timeseries are section- and depth-average along 4 sections covering the deep part of Fram Strait (77.9°–78.9°N, 4.2°W–8.7°E). They were obtained by inversion from the acoustic travel times measured in the thermometry experiment. Such large-scale average measurements in a highly turbulent environment at one of the important sites for ocean circulation in the Arctic are unique and will hopefully increase our understanding of volume and heat exchanges between the Arctic and Atlantic. A regional ocean model of Fram Strait was set up for the assimilation of the ACOBAR measurements using the 4-DVAR data assimilation technique. The forward model part was evaluated using both oceanographic and acoustic measurements (Geyer et al., 2019). First assimilation results show a cost reduction of 85% after 10 iterations. The resulting ocean state estimate will be evaluated using the long-term oceanographic mooring section in Fram Strait at 78°50’N. The aim of this study is to use the ocean state estimate to facilitate the interpretation of the acoustic thermometry results and to investigate how the circulation dynamics in Fram Strait are influencing the volume and heat exchanges through the strait.
Advances in ultrasound imaging: Passive cavitation imaging/mapping
Authors: Gray Michael , Haworth Kevin J.
Published: June 2021

Ultrasound-induced cavitation has been demonstrated to induce numerous bioeffects, including tissue ablation and drug delivery. Different types of cavitation activity (e.g., inertial or stable) nucleate different bioeffects and are associated with distinct regimes of ultrasonic emissions. Thus decades of research have investigated the emission-bioeffect relationship. Since 2008, beamforming of cavitation emissions has been performed to provide images of cavitation activity. This enables the spatio-temporal localization, characterization, and quantification of cavitation activity, which has been shown to have utility in both image-guidance of therapies and basic science studies. The goal of this tutorial is to familiarize participants with the principles and implementation techniques for array-based passive cavitation monitoring. We will begin with a review the fundamentals of time-domain and frequency-domain beamforming, including an opportunity to form images during the tutorial using data and MATLAB code provided by the speakers. Next, we will discuss steps to correct for propagation path and hardware-specific effects in order to provide improved cavitation dose estimates. Display considerations and B-mode duplex imaging topics will follow. Finally, common hardware configurations, including benefits and limitations, will be covered to provide guidance for individuals considering a setup in their laboratory.
A tutorial on the finite and boundary element methods in acoustics
Authors: Hargreaves Jonathan A.
Published: June 2021

The Finite Element Method (FEM) and Boundary Element Method (BEM) are established numerical simulation techniques that are widely used in Engineering, including in Acoustics. This tutorial lecture will give a brief tour of both methods, some discussion of their pros and cons—including when to choose which, or when to use a coupled combination of both—and pointers to commercial and open-source software implementations.
A tutorial on the transfer matrix method for acoustic modeling
Authors: Scavone Gary
Published: June 2021

The transfer matrix method (TMM) is a common technique used to calculate the input impedance or reflectance for 1D acoustic systems that can be approximated in terms of concatenated cylindrical and/or conical sections, as well as side branches. Each section is represented by a transfer matrix that relates frequency-domain expressions of input to output in terms of pressure and volume velocity. This tutorial will provide a brief overview of the TMM formulation, followed by examples using an open-source implementation in Matlab. Methods to derive TMM characterizations for more arbitrarily shaped geometries and extensions for tonehole interactions will also be briefly discussed.
Evaluating the depth capability of underwater thermophone projectors
Authors: Mayo Nathanael K. , Blottman John
Published: June 2021

Thermophones are sound projectors which operate by producing thermally induced gas rarefaction and compression within a thin region adjacent to an electrically heated active element. To enable use underwater and provide protection, the active element can be encapsulated within a housing which is typically backfilled with either an inert gas or a liquid. Until recently, all characterization of underwater thermophones has been conducted at relatively low hydrostatic pressure, within 50 feet of the water’s surface. Hydrostatic pressure tests, Multiphysics simulations, and methods of improving depth capability are discussed as well as an evaluation of the tradeoffs and difficulties associated with improving the performance of these underwater projectors.
Flexoelectric barium strontium titanate (BST) hydrophones
Authors: Hahn Michael , Blanford Thomas , Meyer Richard J. , Trolier-McKinstry Susan
Published: June 2021

Flexoelectric hydrophones offer the possibility of reasonable sensitivity in lead-free systems. Flexoelectricity utilizes strain gradients, rathan the strain, in the case of a piezoelectric. As a fourth rank tensor, flexoelectricity is shown by all solids; the magnitude of the flexoelectric coefficient scales with the relative permittivity, In this work, a Ba0.7Sr0.3TiO3 ceramic with an effective flexoelectric coefficient, ∼μ12, of 105.6 ± 0.6 μC/m at room temperature was utilized in a prototype three-point bending hydrophone. Tap testing with a calibrated acoustic hammer showed a resonant frequency of 250 Hz and a maximum sensitivity of 80 pC/N. Finite element analysis (FEA) was employed to compare single and three bending point hydrophone designs. The results showed a 43% increase in charge output in the three bending point design versus the single bending point design despite an average strain decrease of 48% in each electrode pair. This design would lower the voltage output by 48% in a voltage-based design unless the voltages could be added in series.
The fretted zither and the influence of a supporting table on its initial transients—An impulse pattern formulation model
Authors: Linke Simon , Bader Rolf , Mores Robert
Published: June 2021

Fretted zithers originate in the Alpine region and their adjacent countries. They consist of 5 fretted and 24-37 free vibrating strings stretched across a thin body. The instrument is usually played on a specific table, which is designed to amplify the sound. Thus, the table is crucial for the produced sound and must therefore be considered in respective acoustical analyses. This work explores the influence of various tables and other supporting material on the length and character of initial transients of a played zither tone. Measurements are performed while playing with differently designed tables, with a solid tabletop or with a hollow sound chamber, but while playing without a table, with the instrument placed on one’s knees. As every part of the instrument is coupled to the table, the transients not only depend on the impedance of the support material but also on the plucked string itself. Thus, all components are modeled together. The method of choice is the Impulse Pattern Formulation (IPF) which assumes the zither to work with impulses traveling through the instrument body. During the transition from zither to the table, they get partly reflected, damped, and act back on the string, effectively co-defining the transient behavior.
String choice: Why do harpists still prefer gut?
Authors: Woodhouse Jim , Lynch-Aird Nicolas
Published: June 2021

There are three materials commonly used for non-metallic musical strings: nylon, fluorocarbon and natural gut. Classical guitarists have, almost universally, switched from gut to nylon or fluorocarbon, but many harpists still prefer gut. A design chart for string choice will be presented, and versions of it will be shown for the three materials. These will be used to demonstrate that harpists make a choice of gauges and tensions that contrasts dramatically with the practice of guitarists. This leads them to be interested in a different corner of the design chart, where gut indeed has an advantage over nylon in terms of the internal damping behaviour of bass strings. It will then be suggested that this advantage could be eliminated by the use of fluorocarbon strings, with appropriate gauges, in the lower register of plain strings (without over-winding).
Effects of humidity on natural gut harp strings
Authors: Lynch-Aird Nicolas , Woodhouse Jim
Published: June 2021

Natural gut harp strings are notoriously sensitive to changes in humidity, but the nature of this sensitivity is poorly understood. The results of some recent measurements will be presented, in which a number of well-settled strings were held at constant temperature and subjected to changes in humidity. It will be shown that there appears to be some form of coupling between humidity-induced changes in the string linear density and its tension. Moreover, these changes in linear density and tension largely cancel out, with little net effect on the string frequency. It appears, instead, that the major effect of changes in humidity is to trigger episodes of additional string creep. The longevity of gut harp strings may therefore be determined as much by their propensity to creep as by their breaking strength.
Empirical probability density of sound levels to understand the contribution of mapping sonar to a soundscape
Authors: Kates Varghese Hilary S. , Smith Michael J. , Miksis-Olds Jennifer , Lurton Xavier , Mayer Larry A.
Published: June 2021

Soundscapes—or the characterization of the temporal, spatial, and frequency attributes of the ambient sound and its sound sources—are commonly used to assess the impact of anthropogenic noise-generating events. Large-scale, cabled hydrophone arrays offer a unique opportunity for high-resolution temporal and spatial sampling, providing a comprehensive empirical understanding of the contribution of anthropogenic noise to a soundscape. The Southern California Antisubmarine Warfare Range hydrophone array, which spans 2000 km2 and contains 89 bottom-mounted 50Hz–48 kHz receivers, was used to characterize the marine soundscape during a mapping survey utilizing a hull-mounted 12 kHz multibeam echosounder (MBES). The acoustic data from the array were continuously recorded throughout the approximately two-day survey in January 2017 and used to calculate unweighted decidecade sound levels using standard temporal window lengths and weighted levels with non-standard window lengths motivated by their applicability to marine mammal hearing. The time-dependent contribution of the MBES survey to the unweighted and marine mammal-weighted soundscape was assessed by calculating the probability density of the decidecade sound levels and comparing them spatially for four analysis periods. The analysis periods were: (1) no mapping activity; (2) vessel-only; (3) vessel and MBES; and (4) vessel, MBES, and other active acoustic sources.
Simulating wave propagation in acoustic metamaterials with isogeometric analysis
Authors: Goldsberry Benjamin M. , Wallen Samuel P. , Haberman Michael R.
Published: June 2021

Finite element analysis (FEA) is commonly used to simulate and design acoustic metamaterials (AMM). Numerical studies employing FEA often rely on Bloch-Floquet analysis of a single unit cell or direct numerical simulations that include many unit cells. Unfortunately, AMM unit cells with fine features necessitate dense computational meshes to resolve the geometry and accurately model wave motion, sometimes prohibiting the use of FEA. Isogeometric Analysis (IGA) is a potential alternative approach to FEA for wave propagation problems. IGA utilizes basis functions that are typically employed in Computer Aided Design (CAD) software, such as B-splines and Non-Uniform Rational B-Splines (NURBS), to represent both the geometry and the wave solution. The direct utilization of the CAD geometry eliminates the need for a separate computational mesh of the geometry and the smoothness of the NURBS basis functions provides increased accuracy per degree of freedom. The latter point is particularly useful for high frequency problems. This talk presents IGA as a means to model AMM behavior and compares results with FEA simulations in terms of total simulation time and accuracy. Finally, we comment on the current limitations of IGA and discuss avenues of future research. [Work supported by the ARL:UT postdoctoral fellowship program.]
Laboratory seismic measurements for layer-specific description of fluid mud and for linking seismic velocities to rheological properties
Authors: Ma Xu , Kirichek Alex , Shakeel Ahmad , Heller Karel , Draganov Deyan
Published: June 2021

The velocities of the seismic waves propagating in the fluid-mud layer are governed by the rheological properties and density of the fluid mud. Performing seismic transmission measurements inside the fluid mud can give good estimates of the seismic velocities and, thus, of the rheological properties and density. Laboratory ultrasonic transmission measurements of the wave velocities in the fluid-mud layer and their temporal evolution are shown. It is found that the shear-wave velocity and yield stress are positively correlated. Performing a seismic reflection survey for characterization of the fluid-mud layers could be more practical because it allows towing the sources and receivers above the top of fluid-mud layer. Interpretation of the results from a reflection survey, though, is influenced by the water layer above the fluid mud. Applying seismic interferometry to reflection measurements can eliminate the influence of the water layer and retrieve a reflection response from inside the fluid-mud layer. This eliminates the influence of the temperature and salinity of the water layer to obtain information about the seismic properties of the fluid-mud layer. To introduce the approach of retrieving and extracting the reflection response from inside the fluid-mud layer, data from laboratory measurements are used. The obtained compressional- and shear-wave velocities are validated by comparing them with values from current transmission measurements.
Long-term analysis of ocean ambient noise recorded at the northeast Pacific continental margin
Authors: Munson Matthew , Schwock Felix , Abadi Shima
Published: June 2021

Long-term underwater ambient noise analysis provides valuable insight into the changing soundscape of the ocean. This study evaluates four years of hydrophone data recorded at four locations off the Oregon coast between 2015 and 2019. The hydrophones record the soundscape continuously with a sample rate of 64 kHz and are deployed at depths ranging from 80 to 2900 m. The size of the dataset required processing to be distributed between 32 separate cloud machines. To facilitate long-term analysis, the data are averaged into sequential fifteen minute power spectral density (PSD) estimates. The PSD estimates are used to create long-term spectrograms and time series for various frequencies, which are analyzed for long-term trends and seasonal patterns. Spectrograms and ambient noise time series are used to identify different sound sources such as storms and periods of intense shipping and marine mammal activity. Furthermore, cross-element comparisons of the noise level are made to evaluate the site and depth dependence of the ambient noise. [Work supported by ONR.]
Parallelizing viscoelastic shear wave simulations with MPI and CUDA
Authors: Wiseman Luke M. , McGough Robert J.
Published: June 2021

Three dimensional (3D) simulations of shear wave elasticity imaging (SWEI) are performed by computing a 3D push beam in FOCUS, the “Fast Object-oriented C++ Ultrasound Simulator” (https://www.egr.msu.edu/~fultras-web) followed by the superposition of Green's function solutions to Navier's equation in viscoelastic media. Results show that these Green's function calculations are particularly amenable to parallel implementations that combine MPI and CUDA.
Numerical solutions of the inviscid Burgers equation with the discontinuous Galerkin method
Authors: Holmes Vaughn E. , McGough Robert J.
Published: June 2021

Solutions to the inviscid Burgers equation are numerically computed with the discontinuous Galerkin method with basis functions up to 16th order. Simulation results show that shock waves are effectively modeled and that in the absence of filtering, significant oscillations are observed.
Numerical prediction of hydro-acoustics signature of NACA foils for tidal turbines
Authors: Zhao Dan , Liu Xiran
Published: June 2021

Tidal power is one of the renewable energy sources. The tides produced in the water is used to drive the blade rotation of a tidal turbine for energy conversion. However, the blade rotation produces noises over 10–150 kHz that affect underwater mammals. In this wok, numerical simulations are conducted to predict the hydro-acoustics signature of different NACA foils, which could be used for tidal turbine blades. Finite volume and Ffowcs-WilliamsHawking’s method are used to predict the fluid dynamics and acoustics signatures. We first study the effect of thickness to chord ratio (Tb/cb = 0.1, 0.13 and 0.19) on the noise generation from three different NACA foils (i.e., NACA0012, 0018, and 2410). Hydrodynamic data of these three foils are used for validation of its hydro-acoustics signature. Hydro-acoustics data are acquitted over the propagation distance from 50 m to 2.6 km at different angular positions and at various angles of attack (AOA) (AOA = 0°, 9°, and 15°). To shed lights on the sound generation mechanism, the NACA 2410 foil with vortex generator-produced perturbations is chosen as a case study. Comparison is then made between the prediction and the acoustic data of an actual foil.
Experimental demonstration of a two-dimensional sound diffusing acoustic metasurface with subwavelength thickness
Authors: Kang Janghoon , Haberman Michael R.
Published: June 2021

Acoustic diffusers are surfaces that minimize the strength of room modes in small- and medium-sized rooms and reduce specular reflections in large spaces. Since diffusers are surface treatments that are mounted to walls of interior spaces, it is desirable to reduce their thickness in order to maximize usable space. Traditional diffuser designs, such as the quadratic residue diffuser (QRD) make use of variable depth wells to control the local phase of the reflected field. In these designs, well depth is directly proportional to the reflected phase, rendering the overall thickness dependent on the design frequency. Coiled-space (CS) structures are good candidates to minimize diffuser thickness while maintaining performance. However, CS structures have tortuous channels which are susceptible to viscous losses which can degrade diffuser performance. This work presents a CS design for a 2D QRD (N = 7) diffuser with minimal viscous losses and λ/8 thickness, a 4x reduction compared to traditional QRD. Six unit-cell designs were optimized, fabricated, and measured in an impedance tube. Measured reflection coefficients are in a good agreement with predictions. The 3D diffusion performance of the CS and traditional diffusers were measured on multiple planes orthogonal to the diffuser surface with CS and traditional designs performing comparably.