bluuebunny/crossref_metadata_2025 huggingface dataset:
The quiet project-UK acoustic community’s response to COVID-19
Authors: Dance Stephen , McIntyre Lindsay
Published: June 2021

The COVID-19 Lockdown created a new kind of environment both in the UK and globally, never experienced before or likely to occur again. A vital and time-critical working group was formed with the aim of gathering crowd-source high quality baseline noise levels and other supporting information across the UK during the lockdown and subsequent recovery period. The acoustic community were mobilised through existing networks engaging private companies, public organisations, and academics to gather data in accessible places. A website was designed and developed to advertise the project, provide instructions and to formalise the uploading of noise data, observations, and Soundscape feedback. In addition, pre-existing on-going measurements from major infrastructure projects, airport, and planning applications were gathered to create a data repository of 1.6 GB. The plan was to have regular 6 monthly national noise surveys, which turned into multiple Lockdown surveys. Noise data has been compared to the traffic flow data from the TRIS national wide permanent monitoring system. Ultimately, the databank will be used to establish the relation to other impacts such as air quality, air traffic, economic, and health and wellbeing. As publicly funded research the databank will be made publicly available to assist future research.
Changes in statistical traffic noise descriptors during COVID-19
Authors: Edwards McCall , Dong Wayland , Lo Verde John , Rawlings Samantha
Published: June 2021

Road traffic noise assessments are based on noise indicators, which were traditionally based on long-term average levels such as Ldn and Lnight. Newer regulations also include the “loudest” hourly Leq, although the loudest hour is not defined nor is any guidance provided for determining it. Previous work has focused on methods for estimating these noise indicators from short-duration measurements and determining the uncertainty and reliability of those estimates. The analyses were based on statistical analyses of time history noise levels recorded at various cities across Connecticut and California as well as Dublin, Ireland [King et al., in Noise-con (2016)]. Preliminary analysis of the changes in traffic patterns during to the COVID-19 pandemic showed that the hourly and daily variability increased significantly, with implications for the uncertainty of noise descriptors estimated from measurements. In this paper, an additional six months of traffic data are presented. The analysis presented looks at how the increased variability affects the definition and measurement of both average and loudest hourly levels and the uncertainties of the measurements.
The iterative nonlinear contrast source method for simulating ultrasound propagation through a polydisperse microbubble population
Authors: Matalliotakis Agisilaos , Verweij Martin D.
Published: June 2021

Multiple scattering of sound by a population of particles attracts scientific interest for many decades. In contrast-enhanced echography, the simulation of ultrasound propagation through a dense cloud of nonlinearly oscillating microbubbles imposes a numerical challenge. This is particularly the case for polydisperse concentrations in which each scatterer has individual and independent properties. To address this problem, the Iterative Nonlinear Contrast Source (INCS) method has been adapted. Originally, this solved the Westervelt equation by letting its nonlinear term represent a contrast source in a “linearized” medium, and iteratively updating the pressure by computing the 4D spatiotemporal convolution between this source and the Green’s function. Because convolution allows a coarse discretization, INCS is suitable to deal with large-scale problems. In this talk, microbubbles are regarded as nonlinearly responding point sources that act as contrast sources. The total scattered pressure is computed iteratively, as in the original method, but now in each iteration the temporal signature of the contrast sources is calculated by solving every bubble’s own Marmottant equation. Physically, each iteration accounts for an order of multiple scattering. Numerical results will also be presented, demonstrating that INCS can accurately and efficiently simulate ultrasound propagation through a 3D population of polydisperse nonlinear microbubbles.
Reconsidering reading span as the sole measure of working memory in speech recognition research
Authors: Bosen Adam K.
Published: June 2021

Although it is generally accepted that speech recognition depends on working memory, it can be difficult to delineate the roles of different aspects of working memory in speech recognition. A limitation of many studies relating speech recognition and working memory is the reliance on a single measure of working memory, often reading span. While reading span is a valuable assessment of working memory, its association with several aspects of cognition makes its connection to speech recognition difficult to interpret when used in isolation. Here, we present the benefits of using a combination of different stimuli, listening conditions, and tasks to assess working memory. By varying the stimuli and listening conditions in a serial recall task we isolated serial recall ability from difficulty identifying words in adverse listening conditions. Separating these aspects allowed us to characterize their relationship with vocoded sentence recognition. We also found that recognition of vocoded speech in the presence of two-talker competing speech was precited to the same extent by serial recall, free recall, and reading span tasks, which indicates that alternative tasks are viable for assessing the aspects of working memory which support speech recognition. We encourage assessing working memory ability with multiple short memory tasks.
Categorical perception: Lessons from an enduring myth
Authors: McMurray Bob
Published: June 2021

Categorical perception holds a unique place in cognitive science. In terms of its impact on other fields, it is likely the most impactful finding in speech perception over the last 60 years. However, within speech perception, it is widely known to be largely an artifact of task demands. Categorical perception is empirically defined as a relationship between phoneme identification and discrimination. As discrimination tasks do not appear to require categorization, such linkage violates psychophysical laws and was thought to support the claim that listeners perceive speech solely in terms of linguistic categories. However, 50 years of work using a variety of discrimination tasks, priming, the visual world paradigm, and event related potentials has roundly rejected this account. In this talk, I explore the origins and impact of this scientific meme and the work challenging it. This leads to a new understanding of how to use and interpret some of the most basic techniques of speech—phoneme identification along a continuum—and to new ways of understanding the role of sensitivity to withing category variation. This has major implications for understanding language and hearing disorders and development.
Glider-based passive bottom reflection-loss estimation: Proof of concept
Authors: Muzi Lanfranco , Schecklman Scott , Siderius Martin , Nielsen Peter L.
Published: June 2021

This study presents the proof of concept, based on data collected by a flying glider, for extending the capabilities of autonomous underwater vehicles to the passive measurement of the seabed reflection loss, an important contributor to the transmission loss in shallow water scenarios. During the GLISTEN 15 experiment, a Slocum glider was equipped with an advanced acoustic multi-channel payload coupled with a nose-mounted eight-element vertical line array of hydrophones. By processing the ambient-noise field generated by wind and breaking waves at the surface, recorded while the glider is quietly hovering over the seabed, the system provides an entirely passive, in situ measurement of the bottom power reflection coefficient as a function of frequency and grazing angle. The theoretical foundations and the algorithms for processing the data are summarized and applied for the first time to data collected by a linear array mounted on a flying glider. The results are compared to those obtained by arrays moored in the vicinity of the glider during the same experimental campaign. The possibility of recovering the layering structure of the bottom by passive fathometry is also discussed.
Underwater navigation via spiral wave front beacon
Authors: Dzikowicz Benjamin , Yoritomo John , Hefner Brian T. , Brown David A. , Bachand Corey L.
Published: June 2021

Experiments carried out at NUWC’s Seneca Lake facility in the summer of 2020 demonstrate the efficacy of navigating via a single spiral wave front (SWF) beacon. A set of experiments were performed where an Unmanned Underwater Vehicle (UUV) operating in Seneca Lake under various channel conditions receives a regular signal from a single SWF beacon. The UUV’s aspect relative to the beacon and its radial velocity can be determined by comparing the phase of a specially generated spiral wave front signal to that of an omnidirectional reference signal. Comparison of the SWF navigation solutions to the UUVs inertial/GPS navigation solutions will be presented for various geometries. This talk will also discuss how this technology can be used to navigate the UUV in GPS denied environments, how it compares to other acoustic navigation systems, and its robust operation in multipath environments. (Work sponsored by the Office of Naval Research.)
Deriving an acoustic-based abundance estimate for porpoise species in Pacific Canadian waters
Authors: Ferguson Elizabeth , Doniol-Valcroze Thomas , Nichol Linda
Published: June 2021

The Pacific Region International Survey of Marine Megafauna was conducted in the summer of 2018 to determine the distribution and abundance of cetaceans within the coastal and offshore waters of Canada. Tom Norris led the passive acoustic monitoring operations for this survey, and his Bio-Waves team of bioacousticians conducted 24-hour linear towed hydrophone array monitoring. Ocean Science Analytics worked in partnership with Bio-Waves, Inc. to conduct a post-processing analysis of this dataset and obtain an acoustic-based abundance estimate of porpoises by localizing individual click trains. Data were first re-processed in PAMGuard to reduce confounding noise and improve click classification. High-pass filters were used to reduce noise, and narrow-band, high-frequency (NBHF) echolocation clicks were up-sampled to improve the time delay measurement. The average peak frequency of clicks was used to determine their likely categorization as Dall’s (Phocoenoides dalli) or harbour (Phocoena phocoena) porpoise. Of the 90 NBHF clicks trains detected, 78 were categorized as Dall’s porpoise, and 56 yielded localizations. The resulting acoustic-based Dall’s porpoise abundance estimate (3967, CV 29%) was considerably lower than the visual-based estimate (27 002, CV 23%). We discuss possible reasons for this discrepancy and new insights into porpoise occurrence and distribution within the study area.
Modelling statistics of sonic boom parameters in turbulent media using nonlinear parabolic equation
Authors: Yuldashev Petr V. , Karzova Maria M. , Khokhlova Vera , Blanc-Benon Philippe
Published: June 2021

Over the past decade, plans to develop a new generation of supersonic passenger aircrafts have spurred interest in sonic boom propagation in the atmosphere. New designs are focused on reducing its loudness on the ground. Sonic boom waves are affected by propagation in turbulence of the planetary boundary layer occurring in few kilometers above the ground. Therefore, sonic boom wave parameters such as peak pressure and rise time, as well as corresponding noise levels, become random, which requires statistical characterization. Theoretical analysis of the effects of the presence of turbulent layer is frequently based on one-way model equations of different complexity, of which the basic equation is the nonlinear parabolic Khokhlov-Zabolotskaya-Kuznetsov-type (KZK) equation. Here, sonic boom propagation through homogeneous isotropic turbulence is simulated using the KZK equation. Classical N-waves with different amplitudes and several examples of low-boom waveforms are considered as input waveforms at the entrance to turbulent layer. Statistical data of the peak pressure, shock front steepness, and perceived loudness metric are analyzed. It is shown than unless sonic boom amplitude exceeds a certain threshold, perceived loudness variability is mainly determined by waveform spectral components at mid-range frequencies around 100 Hz. [Work supported by RSF-18-72-00196 and ANR-10-LABX-0060/ANR-16-IDEX-0005.]
One-dimensional harmonic scattering from a localized damage modeled as symmetric and asymmetric hysteretic nonlinearity
Authors: Ghodake Pravinkumar R.
Published: June 2021

A monochromatic ultrasonic wave propagating in damaged material modeled as quadratic, cubic, and hysteretic nonlinearities generates higher harmonics as reported in various theoretical, computational, and experimental studies. In metals under fatigue, certain grains get plastically deformed due to their preferentially oriented slip planes in certain regions and form localized damages like slip bands and micro-cracks. To capture the complex nature of the locally damaged material, local damage is modeled as symmetric and asymmetric hysteretic nonlinearity in this study. A one-dimensional domain is discretized as a long spring-mass chain with few spring-mass elements at the center of a domain modeled as hysteretic elements. Both the back and forward scattered waves from the symmetric hysteretic model contain only odd harmonics and in an asymmetric hysteretic model, both the odd and even harmonics observed. The amplitude of fundamental harmonics of the forward scattered wave decreases with an increase in local damage size and the amplitudes of higher harmonics increases due to an energy transfer from fundamental harmonics in both symmetric and asymmetric hysteretic models. Due to interference of backscatterd waves from two interfaces of local damage, backscattered higher harmonics amplitudes shows increasing and decreasing nature with an increase in local damage size.
Broadband global acoustic cloaking experiments
Authors: Becker Theodor S. , Robertsson Johan O. , van Manen Dirk-Jan
Published: June 2021

Rendering objects invisible to impinging acoustic waves (i.e., acoustic cloaking), is a mature topic in the acoustic community and has diverse applications. Nevertheless, existing approaches and physical demonstrations still exhibit a large range of assumptions and limitations. Passive approaches, which surround the scattering object with a suitable (meta-)material, are usually only effective in a narrow frequency-band and cannot adapt to changing incident fields. Active approaches, which rely on the emission of a secondary wavefield that destructively interferes with the scattered field, have the potential to respond dynamically and be broad band. However, without knowledge of the primary or scattered field, the signals for the secondary sources need to be estimated from wavefield measurements in real-time. To our knowledge, this was never demonstrated beyond 1D acoustic experiments to achieve global broadband control of forward- and backscattered waves. Here, we present experimental results of active, broadband 2D acoustic cloaking without any assumptions of the primary or scattered wavefields. Using a low-latency control system and a dense array of control microphones, the signals for 20 control sources surrounding the scatterer are estimated and applied in real-time to achieve fully deterministic, global acoustic cloaking.
Teaching underwater acoustics and sonar during the COVID pandemic
Authors: Korman Murray S. , Burge Leah E.
Published: June 2021

USNA’s Underwater Acoustics and Sonar (SP411) course, taught in a studio classroom, can seat 36 students with 5 experimental/computer workstations on each side of the classroom. This non-laboratory course relies on hands-on demos and in-class mini-laboratory experiences bringing theoretical concepts and experimental aspects of sound propagation and detection theory to life. Experiments include: (a) sound speed versus temperature in water, (b) beam pattern functions versus angle for multi-element arrays, (c) Fourier analysis of periodic waveforms including rectangular pulses, and (d) square law detection of signals plus noise—generating receiving operating characteristic ROC curves. Computer visualizations using Mathematica included phasor addition of signals, N-element array superposition for directivity analysis and a user friendly ray tracing program implementing any sound speed versus depth profile. On 20 March, 2020, the USNA entered the pandemic era by requiring remote learning for all 4100 midshipman, commencing shortly after spring break. Remote learning in SP411 was asynchronous, devoid of lectures, including handouts and videos of wave effects and worked examples. Mathematica visualizations replaced experiments and extra instruction (in different time zones) was always available. Co-author LEB’s photoacoustic imaging experiments, done remotely, used homemade electronics (pulsed LED driver and low-noise amplifiers)—keeping future midshipmen research going.
Active sonar target classification using a physics-cognizant feature representation
Authors: Kubicek Bernice , Sen Gupta Ananya , Kirsteins Ivars
Published: June 2021

Active sonar target classification is challenging due to the non-linear overlap of changing oceanic and target parameters, creating entangled acoustic color spectra that should be disentangled prior to classification. A physics-cognizant feature extraction algorithm, used before interfacing with three machine learning techniques for active sonar target classification of experimental field data, is presented. The feature extraction algorithm convolves a two-dimensional Gabor wavelet across acoustic color spectra prior to threshold-based binarization, feature culling, and dimensional reduction. The optimal two-dimensional Gabor wavelet parameters are chosen through sensitivity analysis by a support vector machine (SVM) on a disjoint subset of data. Classification is performed on the second subset of data with an SVM, random forest tree, and neural network on the Gabor filtered spectra and unfiltered spectra to show the increased classification accuracy of the application of the geometric wavelet. Classification results are presented as confusion matrices for four targets of two public domain experiments. Ongoing and future work will include extending this feature extraction technique using various geometric feature representations to capture and describe far-field large scattering mechanisms from targets such as oil rigs, tankers, and shipwrecks. [This research is funded by the Office of Naval Research under Grant No. N00014-19-1-2436.]
Representation of bioacoustic sound data through graphical similarities to enhance knowledge discovery
Authors: McCarthy Ryan A.
Published: June 2021

Autonomous detection and classification of species through bioacoustics sound has been an ongoing and challenging problem due to noise, overlapping sound, and varying frequency components. This work assesses bioacoustic sound data through speech patterns similarities by utilizing graphical representations of features found in spectrograms. Speech within the received sound can be characterized as individual components within the spectrogram that can be used to identify species. In this work, individual components are connected high PSD dB values in the spectrogram that form unique shapes. By representing these components through graphical representations, similarities of speech can be seen as repeating patterns across larger collected data sets that can be associated with certain behaviors of species. An example resulting graphical representation is presented through a sample humpback whale speech collected. [This research is funded by the Office of Naval Research under Grant No. N00014-19-1-2609.]
International collaboration on acoustics Orchestrating five essential elements
Authors: Chung Andy W. , Schulte-Fortkamp Brigitte
Published: June 2021

E—empowering knowledge transfer X—eXtending application of acoustics to other sectors C—capacity building “rethink” E—engaging stakeholders & community L—long term strategic management towards healthy and harmonised cities/societies
Spatial variability of epi- and mesopelagic backscattering layers remains relatively constant over multi-year monitoring across the southeastern U.S. shelf break
Authors: Blair Hannah , Miksis-Olds Jennifer , Warren Joseph
Published: June 2021

Acoustic echosounders can measure the distribution and abundance of pelagic organisms over varying spatial and temporal scales. The spatial variability of 38 kHz backscatter along the U.S. Mid- and South Atlantic continental slope was measured from ship-based surveys (50–100 km2) at seven sites over a four year period. We used variogram analysis to estimate the horizontal spatial structure of backscatter measurements and examined how these varied among sites, across years, and with environmental factors. Average patch sizes were consistently between 2 and 4 km for surveys across time and location. Modeled variogram range varied significantly with the depth of the backscatter layer, but linear effect sizes were negligible (<1m). Chlorophyll a (chl-a) concentration had a significant positive effect on range (95 m), suggesting patch sizes are slightly larger in the epipelagic where chl-a concentration is higher. Incorporating variogram range, sill, and nugget produced some clustering of backscatter spatial autocorrelation with depth, particularly for the deepest sites assessed. These results offer insight into nekton and macrozooplankton backscatter patterns in important shelf slope systems, and provide needed information to design accurate long-term monitoring programs for offshore marine habitats. [Work supported by BOEM/ONR/NOAA under NOPP]
H-scan analysis of subtle changes in scattering
Authors: Parker Kevin J.
Published: June 2021

The H-scan analysis provides a matched filter approach to quantifying the scattering transfer function of tissue, at high resolution, in medical ultrasound. The approach yields quantitative estimates and high resolution images where color encodes the scattering information, and the results on normal and diseased tissues will be presented.
Towards real-time super-resolution imaging with fastAWSALM
Authors: Riemer Kai , Toulemonde M. , Lerendegui M. , Christensen-Jeffries K. , Harput S. , Zhang G. , Dunsby C. , Tang M-X
Published: June 2021

Localization-based ultrasound super-resolution imaging can visualize the microvascular structure beyond the diffraction limit but is sensitive to contrast concentration and requires acquisition for seconds. Low-boiling-point phase-change nanodroplets achieve super-resolved images with subsecond temporal resolution through activation and destruction with high frame rate plane waves in real-time.
Image compositing for simultaneous passive imaging of stable and inertial cavitation
Authors: Lafond Maxime , Kennedy Sonya , Salido Nuria G. , Haworth Kevin J. , Hannah Alexander S. , Macke Gregory P. , Genstler Curtis , Holland Christy K.
Published: June 2021

For image guidance of ultrasound-mediated drug delivery using Definity® infusions through the Ekosonic Endovascular System (Boston Scientific, Arden Hills, MN), composite cavitation images were formed using ultraharmonic and inharmonic energy values in the green and red channels, respectively, and overlayed on B-mode images. The extension of the traditional 1D color bar to a 2D color map enabled simultaneous display of ultraharmonic and inharmonic energy, coupled with B-mode imaging for spatial localization.
The role of bubbles in twinkling on pathological mineralizations
Authors: Rokni Eric , Simon Julianna C.
Published: June 2021

The Doppler ultrasound twinkling artifact has been attributed to scattering off microbubbles on and within kidney stones; however, it is not clear if microbubbles are also present on other pathological mineralizations. Uric acid, cholesterol, calcium oxalate, and calcium phosphate crystals (n = 5/type) were grown in the lab and imaged with Doppler ultrasound in ambient and hyperbaric conditions to show that microbubbles are present and causetwinkling on mineralizations other than kidney stones. [Work supported by NSF CAREER Grant No. 1943937 and NSF GRFP Grant No. DGE1255832.]
Tuning idiophone bar torsional modes with three-dimensional cutaway geometries
Authors: Beaton Douglas , Scavone Gary
Published: June 2021

The bars of marimbas, vibraphones and similar idiophones are tuned by shaping their “cutaway” or “undercut” geometries. Makers commonly shape bar cutaways to tune three flexural modes of vibration. The first flexural mode is tuned to the fundamental frequency of the bar’s musical note. Two other flexural modes are tuned such that their frequencies become specific multiples of the fundamental. The remaining flexural modes and all other modes are left untuned. Makers have complained of untuned torsional modes polluting bar timbre over specific sections of the keyboard. In wooden marimba bars this problem has proven difficult to predict, filling reject bins with valuable tonewood. This work investigates tuning these torsional modes by varying bar cutaway geometry in three dimensions. No additional mass or heterogeneous materials are employed. Modal frequencies are determined via finite element analysis. Mode shapes are identified algorithmically, enabling analyses to explore the parameter space unsupervised. Geometries are tuned using a gradient-based search method. The approach, designed to efficiently solve underdetermined systems with multiple objectives, is readily applicable to other problems. A selection of tuned example models will be showcased, including rosewood and aluminum bars with common and uncommon tuning ratios.
Analyzing spectral envelope position and shape in a large set of sustained musical instrument sounds
Authors: Siedenburg Kai , Jacobsen Simon , Reuter Christoph
Published: June 2021

It has been argued that the relative position of spectral envelopes along the frequency axis serves as a cue for musical instrument size (e.g., violin versus viola) and that the shape of the spectral envelope encodes family identity (violin versus flute). However, the extent to which spectral envelope position and shape are affected by fundamental frequency (F0), F0- register within instruments, and dynamic level has never been rigorously quantified across a representative set of musical instrument sounds. Here, we analyzed sounds from 50 sustained orchestral instruments sampled across their entire range of F0s at three dynamic levels. Linear regression of spectral centroid (SC) values that index envelope position indicated that smaller instruments possessed higher SC values in most instrument classes, but SC also correlated with F0 and was strongly and consistently affected by the dynamic level. Instrument classification using relatively low-dimensional cepstral audio descriptors allowed for discrimination between instrument classes with accuracies beyond 80%. Envelope shape became much less indicative of instrument class whenever the classification problem involved generalization across dynamic levels or F0-registers. These analyses confirm that the spectral envelope encodes information about instrument size and family identity and highlight its strong dependence on F0 (-register) and dynamic level.
Recognition of sound source components in soundscape based on deep learning
Authors: Yang Ming
Published: June 2021

Sound source components are a crucially important aspect in soundscape, since humans’ perception and evaluation of soundscape strongly depend on the recognition of the constituent sound sources of the acoustic environment. Over the last few years, numbers of studies examined the methods of automated recognition of environmental sound sources/events using machine learning technology. However, the recognition of sound source components in soundscapes remains a challenge for real applications. This present study utilizes the deep learning, a latest developed and advanced machine learning technology, to develop an algorithm to solve this challenge. Without manually extracted acoustic or psychoacoustic features based on expertise, this algorithm automatically extracts features from the spectrogram representation of the sound signals and makes the recognition. It produces the sound source components recognized in the acoustic environment and their respective present time. The algorithm achieves high recognition accuracy, based on binaural recordings of outdoor acoustic environment. For new recordings, i.e., test samples, the recognition accuracies vary from 81.3% to 100%, depending on the specific sound source. This algorithm developed can greatly help soundscape research, and can be applied in automatic soundscape description of sound source components, prediction of soundscape perception and evaluation, and soundscape management.
A socio-technical model for soundmapping community airplane noise
Authors: Park Tae Hong
Published: June 2021

Modern megacities around the world are exemplified by extraordinary population densities, ground transportation omnipresence, and breathtakingly busy airports that operate day and night. And while airports act as critical city infrastructures from economic, employment, and transportation perspectives, assessing noise resulting from the constancy of flyover aircraft is challenging, in part due to the lack of noise measurements. Additionally, community noise reporting yield mostly qualitative data which further renders community noise assessment difficult. Citygram, in partnership with GetNoisy, employs a socio-technical model to enable the creation of data-driven, community-accessible spatio-temporally granular airplane noise maps. The technology layer is comprised of edge compute sensor devices, cloud server, and web-based user dashboard that automatically identifies, tracks, and tags airplane events with timestamps, decibel levels, 3D positions, tail numbers, and speed. The social layer enables community engagement and facilitates rapid sensor network scaling. This socio-technical airplane soundmapping model, we believe, can be applied to practically any neighborhood as it harnesses and integrates state-of-the-art smart noise sensing technologies, environmentally incentivized communities, existing community resources, and participation workflows that are necessary in rendering a scalable and cost-effective airplane noise soundmapping system.
The role of technology in creating community participation in soundscape projects
Authors: Leonardson Eric
Published: June 2021

For those who seek to engage diverse, multi-generational communities in urban soundscape awareness, this paper examines the social and creative roles of technology and collaborators in fostering networks and participation in public projects. The author— an experimental improvised music performer, sound artist/designer, and educator—explores models for social practice and public engagement in acoustic ecology as introduced through soundwalks, handmade electronic instruments, and field recording. The importance of inclusive approaches to programming, access to recording and other technologies, attraction through thematically focused events, listening as somatic process, and the role of institutional support, are described. Underlying these topics is a “do it yourself” (DIY) ethic of equity and collaboration with neighborhood community leaders as catalysts for using the power of narrative to build and influence soundscape awareness, thereby creating agency for local residents in shaping their own acoustic environments. Informed by Leonardson's extensive firsthand experience, the importance of art and science collaboration, balanced and informed use of new mobile technologies, the challenges of grassroots volunteer organizing, teaching in higher education and designing youth workshops, are among other ear-minded points and pursuits to be discussed.
Towards a new understanding of the concept of quietness
Authors: Tsaligopoulos Aggelos , Kyvelou Stella , Votsi Nefta E. , Karapostoli Aimilia , Economou Chris , Matsinos Yiannis
Published: June 2021

Sound is an inseparable part of the living environment and the liveability of the city, whilst environmental noise is a major stressor affecting the urban environment. Several approaches have been applied for its mitigation and the goal of several strategy plans regards the creation of quietness. “Quietness” as a term retains an ambiguity and it can be described, so far, as the lack of noise that is portrayed by means of intensity. The concept of quietness in the urban environment is revisited, in an attempt to reveal a new understanding of the specific phenomena. In this research, the focus is on setting aside all indicators either measuring intensity or contextual ones and use quantifiable metrics regarding the acoustic environment, thus introducing a new composite index called the Composite Urban Quietness Index (CUQI). CUQI comprises two sub-indicators, the Acoustic Complexity Index and the Normalized Difference Soundscape Index. CUQI was tested in order to verify the results of previous research regarding the identification of Quiet Areas in the city of Mytilene. It was concluded that CUQI is effective even in this early stage of development.
Distortion and losses of sonic booms through turbulent fields
Authors: Lonzaga Joel B.
Published: June 2021

Distortion and losses due to scattering of sonic booms propagating through turbulent fields are investigated using an extended Burgers equation that incorporates an extinction coefficient model previously reported by the author. The extinction coefficient, induced by turbulence, is modeled as a correction to the free field wavenumber using multiple scattering theory. It is a complex-valued function whose real part leads to a frequency dependent attenuation while the imaginary part results in additional dispersion of sonic booms. Numerical calculation of the extinction coefficient is validated using an exact solution derived for a turbulent field with an exponentially decaying correlation function. The model is suitable for direct integration into any Burgers equation that only accounts for geometrical spreading, nonlinear, and atmospheric absorption effects. The extended Burgers equation lends itself to a very efficient algorithm compared to other sonic boom numerical models developed to account for turbulent fields. The algorithm is then used to model sonic boom waveform distortion and loudness variability through randomly generated, realistic turbulent fields. The effects of the intensity and correlation length of the turbulence on the loudness of N-waves and shaped booms are examined and will be presented.
Complex ray tracing algorithm for infrasound propagation in the atmosphere
Authors: Zelias Annie , Coulouvrat François , Gainville Olaf
Published: June 2021

A classical long standing challenge for the infrasound research community is explaining frequently observed infrasound arrivals into shadow zones. This arrivals can be obtained by generalising standard ray method to complex ray tracing, which takes into account diffraction effects. This method is applied to long range infrasound propagation in a stratified and moving atmosphere by a three step numerical algorithm computing both real and complex eigenrays. First, real rays shooting allows to locate caustics and shadow zones. Second, extrapolation around caustics provides real and complex rays initial guesses. Third, their optimisation is performed using an adaptive algorithm. This process provides wave arrival times, azimuths, apparent velocities and over-pressures at a set of stations. Algorithm efficiency and robustness are illustrated by numerical examples: the ground sonic boom of a slightly supersonic aircraft (Mach cut-off problem), explosion at a ground-based point source, and the sonic boom from a meteorite atmospheric entry. In this last case, a 2D model has been developed inspired by the well-documented Carancas meteorite. Finally, comparisons are performed with other numerical methods.
Investigation of distortion product otoacoustic emission in humans using a nonlinear mechano-electro-acoustic model of the cochlea
Authors: Agarwal Naman , Ramamoorthy Sripriya
Published: June 2021

Nonlinear response component (2f1-f2) measured in the ear canal when two primary tones at f1 and f2 are presented to the mammalian cochlea, is termed as distortion product otoacoustic emission (DPOAE). Whether the mechanism of propagation of distortion product (DP) from the cochlea toward the middle ear, via fast compression waves in fluid or via slow traveling waves on the basilar membrane, is still being debated. In the current study, the computational mechano-electro-acoustic nonlinear cochlea model is used to predict the location and propagation of DP. The three-dimensional model has two fluid-filled ducts coupled with BM and OHC somatic feedback motility coupled to nonlinear HB mechanotransduction, which is the source of nonlinear distortion in the model. The Puria-Allen transmission line model is used for the middle ear. For solving the nonlinear cochlea model dynamics, the alternating time-frequency method is used. The model parameters are adapted to the human cochlea to help understand DPOAE in humans. Preliminary results based on the model will be discussed.
Ripple density resolution in the presence of an additional rippled pattern
Authors: Tomozova Marina , Supin Alexander , Nechaev Dmitry I. , Milekhina Olga N.
Published: June 2021

Rippled-spectrum signals are known for measurements of ripple density resolution. Such signals used previously had uniform ripple patterns across the entire signal’s frequency band. In the present study, signals consisted of two overlapping test and additional patterns with different ripple densities. Ripple density resolution in the test signal was measured as a function of ripple density in the additional pattern. Two discrimination tasks were conducted: either discrimination between a rippled test signal and rippled reference signal or a non-rippled reference signal. The additional pattern reduced the resolution of the test signal in general. For a rippled reference signal, the effect of the additional pattern could be explained by decreased ripple depth in the test signal. For a non-rippled reference signal, the resolution of the test signal was lower for a rippled than for a non-rippled additional pattern. In such a case, there was no dependence on the density of ripples in the additional pattern. The last cannot be explained by a decrease of the ripple depth and was interpreted as a manifestation of temporal processing equivalent to the reveal of a delayed segment of the autocorrelation function of the test signal. [This study was supported by Russian Foundation for Basic research, Grant No. 20-015-00054.]
A model of cortical timbre classification using spike latency coding
Authors: Dahlbom David A. , Braasch Jonas
Published: June 2021

Earlier modeling studies of spiking neural networks with conduction delays have shown that temporally precise, distributed spike patterns (polychronous groups) contain more information about timbral distinctions than firing rates. Additionally, experimental work in auditory cortex has suggested that the initial onset of firing activity is especially important for encoding timbre, an observation that is in accordance with psychoacoustical evidence that the onset characteristics of a stimulus can have a profound effect on the perception of timbre. These observations are combined in a model that uses spike latency to make timbral classifications. A simplified spiking model of the subcortical auditory system is connected to a reservoir of spiking point neurons with cortex-like connectivity statistics and conduction delays. Stimuli are presented to the model in an unsupervised manner, and synaptic strengths are adapted via a spike-timing-dependent plasticity mechanism. After training, a stochastic search algorithm is used to find stimulus-triggered firing patterns generated in the reservoir, the firing latency of which can be used to make accurate timbral categorizations of novel stimuli. The stimuli consist of FM-synthesized instrument sounds (two categories) with varying pitches, demonstrating the model’s ability to learn timbral distinctions in a manner invariant with respect to changes of pitch.
Unit cell interactions of non-local active acoustic media
Authors: Geib Nathan , Popa Bogdan-Ioan , Grosh Karl
Published: June 2021

Active acoustic metamaterials have greatly expanded upon the unique and unusual ways that passive metamaterials manipulate sound. Previously, we have shown how spatially non-local forces in an acoustic system can create band gaps and break acoustic reciprocity, and how such effects can be realized in practice using a non-local active acoustic metamaterial (NAM). We demonstrated experimentally the remarkable ability of a single NAM unit cell to generate large, subwavelength, broadband nonreciprocity using an open loop feedforward control mechanism where a measured local pressure is transmitted by an electronic controller downstream to actuate an acoustic source. In NAM systems with multiple unit cells, this control scheme strongly couples each cell with every other cell, and thus requires special design considerations. Here, we discuss the advantages and challenges of developing NAM systems with multiple unit cells by first considering a system with two cells, detailing the impacts of their complex interaction on both performance and stability. We validate model predictions with experiments and highlight the exciting prospects offered by larger multi-cell NAM arrays.
Tips for collecting self-recordings on smartphones
Authors: Freeman Valerie
Published: June 2021

The COVID-19 pandemic has challenged phoneticians to adopt remote methods of collecting recorded speech. For many research questions, remote collection presents enough logistical benefits to balance the reduced control over recording conditions, allowing us to expand our toolkits and reach more participants quickly and cheaply, even after the pandemic subsides. A current study of multiple vowel mergers provides a successful example of collecting talker-supplied recordings on smartphones and laptops. In two months, over 90 talkers made good-quality 10-min recordings of read words and passages. The short procedure and $5 e-compensation bolstered this success, but smartphone familiarity skewed the sample toward young, educated respondents, necessitating adaptations for less tech-savvy older adults. These and other methodological challenges will be addressed with tips and lessons learned: simplifying task design for increased response rates and compliance, successful approaches to online recruiting and compensation, considerations for populations with poor tech access/skills, and maximizing audio quality within logistical constraints. Recent work will be referenced to support the quality of homemade recordings, with suggestions for determining their suitability for any acoustic measures. Throughout the talk, various tradeoffs will be highlighted: quality/quantity, breadth/depth, control/access, complexity, speed, cost.
A computational Bayesian approach to machine learning of an acoustic scatterer's state of motion in a refractive propagation environment under a small aperture constraint
Authors: Gendron Paul J. , Barros Abner C.
Published: June 2021

A computational Bayesian method for inference regarding the size and state of motion of a submerged mobile object from narrow band transmissions and a small receiver aperture is presented. The challenge of attendant closely spaced multipath arrivals is addressed by taking advantage of knowledge of the refractive environment. Acoustic phase fronts, their angles and Doppler compressed wavelengths are jointly inferred. We take full advantage of the analytic conditional densities of eigenray amplitudes as well as ambient and reverberant power under the conventional Gaussian-Inverse Gamma model and focus computational resources on conditional densities for the frequency-angle dependent wave vectors via sampling from conditional quantile functions. Inversion of the posterior probability density of the wave vectors to the scatterer's state space is accomplished quickly via eigen-ray interpolation. Examples are given from real ocean sound speed profiles as well as the classic Munk profile.
Effect of COVID-19 spring lockdown on low-frequency ambient noise levels along the Brittany coast
Authors: Mathias Delphine , Bonnel Julien , Chauvaud Laurent
Published: June 2021

Shipping noise is a major source of ocean noise in Brest bay, and includes cargo vessels, navy ships, fishing boats and recreational vessels with frequencies overlapping the range of marine animal sound emission. Changes in vessel activity provide unique opportunities to quantify the relationship between traffic levels and soundscape conditions in biologically important habitats. Using an autonomous recorder deployed from March 20 to July 29 2019 inside Sainte-Anne harbor in Brest area we assessed the effect of the 2020 spring COVID-19 lockdown (March 17 to May 11) on ambient noise levels. We measured the mean power spectral density levels in different third-octave bands (including Marine Strategy Framework Directive bands centered on 63 Hz and 125 Hz). The March 20–May 15 (during lockdown) levels were up to 2.6 dB re 1 μPa2/Hz below the May 15–July 28th (after lockdown) levels, corresponding to nearly a halving of acoustic power.
An update to real-time observations of the impact of COVID-19 on underwater sound
Authors: Barclay David R. , Thomson Dugald
Published: June 2021

A slowdown in global trade activity due to COVID-19 has led to a reduction in commercial shipping traffic into the Port of Vancouver. The Ocean Networks Canada observatory system provides researchers real-time access to oceanographic data from a wide range of instruments including hydrophones located along the offshore and inshore approaches to Vancouver. Power spectral density statistics at 100 Hz from four of these bottom mounted hydrophones were monitored, along with AIS data and shipping and trade statistics to assess to what extent the economic impact of COVID-19 can be observed acoustically and in near real-time. The quarterly trend in median weekly noise power in the shipping band of frequencies provides an early indicator that a reduction in noise commensurate with the economic slowdown occurred at two hydrophone stations. Time series of the median and 1st percentile weekly power provide a retrospective detail of the impact of the pandemic on underwater sound.
Multipurpose acoustic networks in the Arctic
Authors: Sagen Hanne , Dzieciuch Matthew A. , Worcester Peter F. , Storheim Espen , Geyer Florian
Published: June 2021

To improve the Arctic Ocean observing capability, OceanObs19 recommends “to pilot a sustained multipurpose acoustic network for positioning, tomography, passive acoustics, and communication in an integrated Arctic Observing System, with eventual transition to global coverage.” A multipurpose acoustic network will widen the wealth of observations of ocean and sea ice variables in the central Arctic. Several regional multipurpose acoustic experiments have been carried out in the Arctic, helping create the capability and experience to go basin wide. The CAATEX (Coordinated Arctic Acoustic Thermometry Experiment) is a first step towards a basin wide multipurpose acoustic system. CAATEX was a one-year limited experiment, but the experiences from the experiment are a forerunner for a sustained Pan Arctic Acoustic Observation Network. This presentation will focus on the planning of and first results from CAATEX and the role of acoustic networks in the future Arctic Ocean Observing System. [CAATEX is supported by Office of Naval Research through Grant No. N00014-18-1-2698 and the Research Council of Norway under Grant No. 280531.]